[SHOW] EXPLAIN UPDATE/DELETE, code re-structuring

- Merge with current 10.0-base

libmysqld/CMakeLists.txt

@@ -99,6 +99,7 @@ SET(SQL_EMBEDDED_SOURCES emb_qcache.cc libmysqld.c lib_sql.cc
            ../sql/sql_expression_cache.cc
            ../sql/my_apc.cc ../sql/my_apc.h
 	   ../sql/rpl_gtid.cc
+           ../sql/opt_qpf.cc ../sql/opt_qpf.h
            ${GEN_SOURCES}
            ${MYSYS_LIBWRAP_SOURCE}
 )

mysql-test/disabled.def

@@ -16,4 +16,4 @@ read_many_rows_innodb    : Bug#11748886 2010-11-15 mattiasj report already exist
 archive-big              : Bug#11817185 2011-03-10 Anitha Disabled since this leads to timeout on Solaris Sparc
 log_tables-big           : Bug#11756699 2010-11-15 mattiasj report already exists
 mysql_embedded           : Bug#12561297 2011-05-14 Anitha Dependent on PB2 changes - eventum#41836
-show_explain  : Psergey: random timeout in range-checked-for-each record query.
+#show_explain  : Psergey: random timeout in range-checked-for-each record query.

mysql-test/r/derived_opt.result

@@ -109,8 +109,8 @@ count(*)
 2
 explain select count(*) from t1 INNER JOIN (SELECT A.E1, A.E2, A.E3 FROM t1 AS A WHERE A.E3 = (SELECT MAX(B.E3) FROM t1 AS B WHERE A.E2 = B.E2)) AS THEMAX ON t1.E1 = THEMAX.E2 AND t1.E1 = t1.E2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	A	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	2	Using where
-1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.A.E2	1	Using where
+1	PRIMARY	t1	eq_ref	PRIMARY	PRIMARY	4	test.A.E2	1	Using where
 3	DEPENDENT SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	2	Using where
 drop table t1;
 create table t1 (a int);

mysql-test/r/derived_view.result

@@ -386,7 +386,7 @@ materialized derived in merged derived
 explain extended  select * from (select * from 
 (select * from t1 where f1 < 7 group by f1) tt where f1 > 2) zz;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	<derived3>	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where; Using temporary; Using filesort
 Warnings:
 Note	1003	select `tt`.`f1` AS `f1`,`tt`.`f11` AS `f11` from (select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f11` AS `f11` from `test`.`t1` where (`test`.`t1`.`f1` < 7) group by `test`.`t1`.`f1`) `tt` where (`tt`.`f1` > 2)
@@ -429,8 +429,8 @@ join
 (select * from (select * from t1 where f1 < 7 group by f1) tt where f1 > 2) z
 on x.f1 = z.f1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	<derived3>	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
-1	SIMPLE	<derived5>	ref	key0	key0	5	tt.f1	2	100.00	
+1	PRIMARY	<derived5>	ref	key0	key0	5	tt.f1	2	100.00	
 5	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where; Using temporary; Using filesort
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where; Using temporary; Using filesort
 Warnings:
@@ -522,7 +522,7 @@ materialized view in merged derived
 explain extended 
 select * from ( select * from v1 where f1 < 7) tt;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	<derived3>	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	11	100.00	Using temporary; Using filesort
 Warnings:
 Note	1003	select `v1`.`f1` AS `f1`,`v1`.`f11` AS `f11` from `test`.`v1` where (`v1`.`f1` < 7)
@@ -568,8 +568,8 @@ f1	f11
 join of above two
 explain extended select * from v6 join v7 on f2=f1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	11	100.00	Using where
-1	SIMPLE	<derived5>	ref	key0	key0	5	test.t2.f2	2	100.00	
+1	PRIMARY	<derived5>	ref	key0	key0	5	test.t2.f2	2	100.00	
 5	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	11	100.00	Using temporary; Using filesort
 Warnings:
 Note	1003	select `test`.`t2`.`f2` AS `f2`,`test`.`t2`.`f22` AS `f22`,`v1`.`f1` AS `f1`,`v1`.`f11` AS `f11` from `test`.`t2` join `test`.`v1` where ((`v1`.`f1` = `test`.`t2`.`f2`) and (`test`.`t2`.`f2` < 7) and (`test`.`t2`.`f2` in (2,3)))
@@ -1220,7 +1220,7 @@ Note	1003	select `test`.`t1`.`b` AS `b` from `test`.`t1` where 0
 EXPLAIN EXTENDED
 SELECT * FROM (SELECT b FROM v2 WHERE b = 0) t WHERE b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using temporary; Using filesort
 Warnings:
 Note	1003	select `v2`.`b` AS `b` from `test`.`v2` where 0

mysql-test/r/explain_non_select.result

@@ -0,0 +1,104 @@
+drop table if exists t0, t1;
+create table t0 (a int) engine=myisam;
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+#
+#  Tests for single-table DELETE
+# 
+explain select * from t0 where a=3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+explain delete from t0 where a=3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+# DELETE without WHERE is a special case:
+explain delete from t0;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Deleting all rows
+create table t1 (a int, b int, filler char(100), key(a), key(b));
+insert into t1 
+select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler' 
+from t0 A, t0 B, t0 C;
+# This should use an index,  possible_keys=NULL because there is no WHERE
+explain delete from t1 order by a limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	a	NULL	NULL	512	
+# This should use range, possible_keys={a,b}
+explain delete from t1 where a<20 and b < 10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a,b	a	5	NULL	1	Using where
+# This should use ALL + filesort
+explain delete from t1 order by a+1 limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	512	Using filesort
+# This should use range + using filesort
+explain delete from t1 where a<20 order by b limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	1	Using where; Using filesort
+# Try some subqueries:
+explain delete from t1 where a < (select max(a) from t0);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	range	a	a	5	NULL	1	Using where
+2	SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	8	
+explain delete from t1 where a < (select max(a) from t0 where a < t1.b);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	512	Using where
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+#
+#  Tests for multi-table DELETE
+# 
+explain delete t1 from t0, t1 where t0.a = t1.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+1	SIMPLE	t1	ref	a	a	5	test.t0.a	4	Using index
+drop table t0, t1;
+# ###################################################################
+# ## EXPLAIN UPDATE tests
+# ###################################################################
+create table t0 (a int) engine=myisam;
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+explain update t0 set a=3 where a=4;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+create table t1 (a int, b int, filler char(100), key(a), key(b));
+insert into t1 
+select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler' 
+from t0 A, t0 B, t0 C;
+explain update t1 set a=a+1 where 3>4;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible where
+explain update t1 set a=a+1 where a=3 and a=4;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible where
+# This should use an index,  possible_keys=NULL because there is no WHERE
+explain update t1 set a=a+1 order by a limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	512	
+# This should use range, possible_keys={a,b}
+explain update t1 set filler='fooo' where a<20 and b < 10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a,b	a	5	NULL	1	Using where
+# This should use ALL + filesort
+explain update t1 set filler='fooo' order by a+1 limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	512	
+# This should use range + using filesort
+explain update t1 set filler='fooo' where a<20 order by b limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	1	Using where
+# Try some subqueries:
+explain update t1 set filler='fooo' where a < (select max(a) from t0);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	range	a	a	5	NULL	1	Using where
+2	SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	8	
+explain update t1 set filler='fooo' where a < (select max(a) from t0 where a < t1.b);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	512	Using where
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+#
+#  Tests for multi-table UPDATE
+# 
+explain update t0, t1 set t1.a=t1.a+1 where t0.a = t1.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+1	SIMPLE	t1	ref	a	a	5	test.t0.a	4	Using index
+drop table t0, t1;

mysql-test/r/limit_rows_examined.result

@@ -439,7 +439,7 @@ from (select * from t1
 where c1 IN (select * from t2 where c2 > ' ' LIMIT ROWS EXAMINED 0)) as tmp
 LIMIT ROWS EXAMINED 11;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
 3	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
 select *
 from (select * from t1

mysql-test/r/selectivity.result

@@ -393,7 +393,7 @@ and not exists (select * from orders where o_custkey = c_custkey)
 group by cntrycode
 order by cntrycode;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
+1	PRIMARY	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
 4	DEPENDENT SUBQUERY	orders	ref	i_o_custkey	i_o_custkey	5	dbt3_s001.customer.c_custkey	15	100.00	Using index
 3	SUBQUERY	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where
 Warnings:
@@ -434,7 +434,7 @@ and not exists (select * from orders where o_custkey = c_custkey)
 group by cntrycode
 order by cntrycode;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
+1	PRIMARY	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
 4	DEPENDENT SUBQUERY	orders	ref	i_o_custkey	i_o_custkey	5	dbt3_s001.customer.c_custkey	15	100.00	Using index
 3	SUBQUERY	customer	ALL	NULL	NULL	NULL	NULL	150	91.00	Using where
 Warnings:

mysql-test/r/selectivity_innodb.result

@@ -396,7 +396,7 @@ and not exists (select * from orders where o_custkey = c_custkey)
 group by cntrycode
 order by cntrycode;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
+1	PRIMARY	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
 4	DEPENDENT SUBQUERY	orders	ref	i_o_custkey	i_o_custkey	5	dbt3_s001.customer.c_custkey	15	100.00	Using index
 3	SUBQUERY	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where
 Warnings:
@@ -437,7 +437,7 @@ and not exists (select * from orders where o_custkey = c_custkey)
 group by cntrycode
 order by cntrycode;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
+1	PRIMARY	customer	ALL	NULL	NULL	NULL	NULL	150	100.00	Using where; Using temporary; Using filesort
 4	DEPENDENT SUBQUERY	orders	ref	i_o_custkey	i_o_custkey	5	dbt3_s001.customer.c_custkey	15	100.00	Using index
 3	SUBQUERY	customer	ALL	NULL	NULL	NULL	NULL	150	91.00	Using where
 Warnings:

mysql-test/r/show_explain.result

@@ -165,7 +165,11 @@ set @show_explain_probe_select_id=1;
 set debug_dbug='+d,show_explain_probe_join_exec_end';
 select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
+Warnings:
+Note	1003	select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1
 a	(select max(a) from t0 b where b.a+a.a<10)
 0	9
 set debug_dbug=@old_debug;
@@ -186,22 +190,38 @@ set @show_explain_probe_select_id=2;
 set debug_dbug='+d,show_explain_probe_join_exec_start';
 update t2 set dummy=0 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
+Warnings:
+Note	1003	update t2 set dummy=0 where (select max(a) from t0 where t2.a + t0.a <3) >3
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
+Warnings:
+Note	1003	update t2 set dummy=0 where (select max(a) from t0 where t2.a + t0.a <3) >3
 drop table t2;
 set debug_dbug=@old_debug;
 #
-# Attempt SHOW EXPLAIN for a DELETE
+# Attempt SHOW EXPLAIN for a DELETE (UPD: now works)
 # 
 create table t2 as select a as a, a as dummy from t0 limit 2;
 set @show_explain_probe_select_id=2;
 set debug_dbug='+d,show_explain_probe_join_exec_start';
 delete from t2 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
+Warnings:
+Note	1003	delete from t2 where (select max(a) from t0 where t2.a + t0.a <3) >3
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
+Warnings:
+Note	1003	delete from t2 where (select max(a) from t0 where t2.a + t0.a <3) >3
 drop table t2;
 set debug_dbug=@old_debug;
 #
@@ -220,13 +240,13 @@ Note	1003	select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ
 show explain for $thr2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
-2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Query plan already deleted
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
 Warnings:
 Note	1003	select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2
 show explain for $thr2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
-2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Query plan already deleted
+2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
 Warnings:
 Note	1003	select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2
 a	SUBQ
@@ -327,7 +347,11 @@ SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a;
 # FIXED by "conservative assumptions about when QEP is available" fix:
 #    NOTE: current code will not show "Using join buffer": 
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using join buffer (flat, BNL join)
+Warnings:
+Note	1003	SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a
 a
 1
 2
@@ -412,7 +436,10 @@ set @show_explain_probe_select_id=1;
 set debug_dbug='+d,show_explain_probe_join_exec_end';
 select * from t0 where 1>10;
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+Warnings:
+Note	1003	select * from t0 where 1>10
 a
 set debug_dbug=@old_debug;
 #
@@ -424,7 +451,10 @@ set @show_explain_probe_select_id=1;
 set debug_dbug='+d,show_explain_probe_join_exec_end';
 select * from t0,t3 where t3.a=112233;
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
+Warnings:
+Note	1003	select * from t0,t3 where t3.a=112233
 a	a
 set debug_dbug=@old_debug;
 drop table t3;
@@ -529,7 +559,12 @@ set @show_explain_probe_select_id=1;
 set debug_dbug='+d,show_explain_probe_join_exec_end';
 SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`);
 show explain for $thr2;
-ERROR HY000: Target is not running an EXPLAINable command
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<subquery2>	const	distinct_key	distinct_key	8	const,const	1	
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	20	Using join buffer (flat, BNL join)
+2	MATERIALIZED	t2	index	NULL	a1	4	NULL	20	Using index
+Warnings:
+Note	1003	SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`)
 pk	a1
 set debug_dbug=@old_debug;
 DROP TABLE t2;
@@ -635,7 +670,7 @@ SELECT a + 1 FROM v1;
 show explain for $thr2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
-2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Query plan already deleted
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	
 Warnings:
 Note	1003	SELECT a + 1 FROM v1
 a + 1
@@ -1045,7 +1080,7 @@ show explain for $thr2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	alias1	ALL	NULL	NULL	NULL	NULL	14	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	20	
-3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Query plan already deleted
+3	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	20	Using where
 Warnings:
 Note	1003	SELECT max(a+b+c) FROM t1 AS alias1, ( SELECT * FROM t2 ) AS alias 
 WHERE EXISTS ( SELECT * FROM t3 WHERE b = c )  OR a <= 10

mysql-test/r/show_explain_non_select.result

@@ -0,0 +1,44 @@
+drop table if exists t0, t1;
+SET @old_debug= @@session.debug;
+set debug_sync='RESET';
+create table t0 (a int) engine=myisam;
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+create table t1 (a int, b int, filler char(100), key(a), key(b));
+insert into t1 
+select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler' 
+from t0 A, t0 B, t0 C;
+#
+# Test SHOW EXPLAIN for single-table DELETE
+#
+set debug_dbug='+d,show_explain_probe_delete_exec_start';
+delete from t1 where a<10 and b+1>1000;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	1	Using where
+Warnings:
+Note	1003	delete from t1 where a<10 and b+1>1000
+#
+# Test SHOW EXPLAIN for multi-table DELETE
+#
+set @show_explain_probe_select_id=1;
+set debug_dbug='+d,show_explain_probe_do_select';
+delete t1 from t1, t0 where t0.a=t1.a and t1.b +1 > 1000;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	8	Using where
+1	SIMPLE	t1	ref	a	a	5	test.t0.a	4	Using where
+Warnings:
+Note	1003	delete t1 from t1, t0 where t0.a=t1.a and t1.b +1 > 1000
+#
+# Test SHOW EXPLAIN for single-table UPDATE
+#
+set debug_dbug='+d,show_explain_probe_update_exec_start';
+update t1 set filler='filler-data-2' where a<10 and b+1>1000;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	1	Using where
+Warnings:
+Note	1003	update t1 set filler='filler-data-2' where a<10 and b+1>1000
+drop table t0,t1;
+set debug_dbug=@old_debug;
+set debug_sync='RESET';

mysql-test/r/subselect.result

@@ -10,7 +10,7 @@ select (select 2);
 2
 explain extended select (select 2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select 2 AS `(select 2)`
@@ -734,7 +734,7 @@ id
 1
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using index
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select `test`.`t2`.`id` AS `id` from `test`.`t2` where (`test`.`t2`.`id` = 1)
@@ -746,7 +746,7 @@ id
 2
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using where; Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using where; Using index
 Warnings:
 Note	1249	Select 3 was reduced during optimization
 Note	1249	Select 2 was reduced during optimization
@@ -880,7 +880,7 @@ select 10.5 > ANY (SELECT * from t1);
 1
 explain extended select (select a+1) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
 Note	1249	Select 2 was reduced during optimization
@@ -4554,7 +4554,7 @@ int_nokey	int_key
 0	0
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
+1	SIMPLE	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
 DROP TABLE C;
 # End of test for bug#45061.
 #
@@ -6112,7 +6112,7 @@ FROM t1 AS sq4_alias1
 WHERE (sq4_alias1.col_varchar_key + NULL) IS NULL OR
 sq4_alias1.col_varchar_key = @var3 ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
 2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
 SELECT * FROM ( SELECT @var3:=12, sq4_alias1.*
 FROM t1 AS sq4_alias1
@@ -6157,7 +6157,7 @@ FROM t2 AS c_sq1_alias1
 WHERE (c_sq1_alias1.col_int_nokey != @var2
 OR c_sq1_alias1.pk != @var3)) ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 3	DEPENDENT SUBQUERY	c_sq1_alias1	system	PRIMARY	NULL	NULL	NULL	1	
 SELECT * FROM ( SELECT sq4_alias1.*
 FROM t1 AS sq4_alias1

mysql-test/r/subselect2.result

@@ -258,7 +258,7 @@ WHERE date < '2012-12-12 12:12:12'
 ORDER BY mirror_date ASC
 ) AS calculated_result;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	range	date	date	9	NULL	2	Using index condition; Using where; Rowid-ordered scan; Using filesort
 SELECT * FROM (
 SELECT node_uid, date, mirror_date, @result := 0 AS result
@@ -281,7 +281,7 @@ WHERE date < '2012-12-12 12:12:12'
 ORDER BY mirror_date ASC
 ) AS calculated_result;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
 2	DERIVED	t1	range	date	date	9	NULL	2	Using index condition; Using where; Using filesort
 SELECT * FROM (
 SELECT node_uid, date, mirror_date, @result := 0 AS result

mysql-test/r/subselect3.result

@@ -1031,7 +1031,7 @@ update t22 set c = '2005-12-08 15:58:27' where a = 255;
 explain select t21.* from t21,t22 where t21.a = t22.a and 
 t22.a in (select t12.a from t11, t12 where t11.a in(255,256) and t11.a = t12.a and t11.c is null) and t22.c is null order by t21.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t11	ALL	NULL	NULL	NULL	NULL	8	Using where; Using temporary; Using filesort; Start temporary
+1	PRIMARY	t11	ALL	NULL	NULL	NULL	NULL	8	Using where; Start temporary; Using temporary; Using filesort
 1	PRIMARY	t12	ALL	NULL	NULL	NULL	NULL	8	Using where; Using join buffer (flat, BNL join)
 1	PRIMARY	t22	ALL	NULL	NULL	NULL	NULL	26	Using where; End temporary; Using join buffer (flat, BNL join)
 1	PRIMARY	t21	ALL	NULL	NULL	NULL	NULL	26	Using where; Using join buffer (flat, BNL join)

mysql-test/r/subselect3_jcl6.result

@@ -1041,7 +1041,7 @@ update t22 set c = '2005-12-08 15:58:27' where a = 255;
 explain select t21.* from t21,t22 where t21.a = t22.a and 
 t22.a in (select t12.a from t11, t12 where t11.a in(255,256) and t11.a = t12.a and t11.c is null) and t22.c is null order by t21.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t11	ALL	NULL	NULL	NULL	NULL	8	Using where; Using temporary; Using filesort; Start temporary
+1	PRIMARY	t11	ALL	NULL	NULL	NULL	NULL	8	Using where; Start temporary; Using temporary; Using filesort
 1	PRIMARY	t12	hash_ALL	NULL	#hash#$hj	4	test.t11.a	8	Using where; Using join buffer (flat, BNLH join)
 1	PRIMARY	t22	hash_ALL	NULL	#hash#$hj	4	test.t11.a	26	Using where; End temporary; Using join buffer (incremental, BNLH join)
 1	PRIMARY	t21	hash_ALL	NULL	#hash#$hj	4	test.t11.a	26	Using where; Using join buffer (incremental, BNLH join)

mysql-test/r/subselect4.result

@@ -93,12 +93,12 @@ DROP TABLE t1,t2;
 #
 EXPLAIN SELECT 1 LIKE ( 1 IN ( SELECT 1 ) );
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 DESCRIBE SELECT 1 LIKE ( 1 IN ( SELECT 1 ) );
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 # None of the below should crash
@@ -520,8 +520,8 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer (flat, BNL join)
 EXECUTE stmt;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	t1_IDX	NULL	NULL	NULL	5	
+1	PRIMARY	t1	ALL	t1_IDX	NULL	NULL	NULL	5	
-1	SIMPLE	<subquery2>	eq_ref	distinct_key	distinct_key	3	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	3	func	1	
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer (flat, BNL join)
 DEALLOCATE PREPARE stmt;
@@ -558,8 +558,8 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer (flat, BNL join)
 EXECUTE stmt;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	t1_IDX	NULL	NULL	NULL	5	
+1	PRIMARY	t1	ALL	t1_IDX	NULL	NULL	NULL	5	
-1	SIMPLE	<subquery2>	eq_ref	distinct_key	distinct_key	3	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	3	func	1	
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer (flat, BNL join)
 DEALLOCATE PREPARE stmt;
@@ -595,8 +595,8 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer (flat, BNL join)
 EXECUTE stmt;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	
-1	SIMPLE	<subquery2>	eq_ref	distinct_key	distinct_key	3	func	1	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	3	func	1	
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 2	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer (flat, BNL join)
 DEALLOCATE PREPARE stmt;

mysql-test/r/subselect_exists_to_in.result

@@ -14,7 +14,7 @@ select (select 2);
 2
 explain extended select (select 2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select 2 AS `(select 2)`
@@ -738,7 +738,7 @@ id
 1
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using index
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select `test`.`t2`.`id` AS `id` from `test`.`t2` where (`test`.`t2`.`id` = 1)
@@ -750,7 +750,7 @@ id
 2
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using where; Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using where; Using index
 Warnings:
 Note	1249	Select 3 was reduced during optimization
 Note	1249	Select 2 was reduced during optimization
@@ -884,7 +884,7 @@ select 10.5 > ANY (SELECT * from t1);
 1
 explain extended select (select a+1) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
 Note	1249	Select 2 was reduced during optimization
@@ -4560,7 +4560,7 @@ int_nokey	int_key
 0	0
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
+1	SIMPLE	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
 DROP TABLE C;
 # End of test for bug#45061.
 #
@@ -6120,7 +6120,7 @@ FROM t1 AS sq4_alias1
 WHERE (sq4_alias1.col_varchar_key + NULL) IS NULL OR
 sq4_alias1.col_varchar_key = @var3 ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
 2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
 SELECT * FROM ( SELECT @var3:=12, sq4_alias1.*
 FROM t1 AS sq4_alias1
@@ -6165,7 +6165,7 @@ FROM t2 AS c_sq1_alias1
 WHERE (c_sq1_alias1.col_int_nokey != @var2
 OR c_sq1_alias1.pk != @var3)) ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 3	DEPENDENT SUBQUERY	c_sq1_alias1	system	PRIMARY	NULL	NULL	NULL	1	
 SELECT * FROM ( SELECT sq4_alias1.*
 FROM t1 AS sq4_alias1

mysql-test/r/subselect_no_mat.result

@@ -17,7 +17,7 @@ select (select 2);
 2
 explain extended select (select 2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select 2 AS `(select 2)`
@@ -741,7 +741,7 @@ id
 1
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using index
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select `test`.`t2`.`id` AS `id` from `test`.`t2` where (`test`.`t2`.`id` = 1)
@@ -753,7 +753,7 @@ id
 2
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using where; Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using where; Using index
 Warnings:
 Note	1249	Select 3 was reduced during optimization
 Note	1249	Select 2 was reduced during optimization
@@ -887,7 +887,7 @@ select 10.5 > ANY (SELECT * from t1);
 1
 explain extended select (select a+1) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
 Note	1249	Select 2 was reduced during optimization
@@ -4556,7 +4556,7 @@ int_nokey	int_key
 0	0
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
+1	SIMPLE	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
 DROP TABLE C;
 # End of test for bug#45061.
 #
@@ -6111,7 +6111,7 @@ FROM t1 AS sq4_alias1
 WHERE (sq4_alias1.col_varchar_key + NULL) IS NULL OR
 sq4_alias1.col_varchar_key = @var3 ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
 2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
 SELECT * FROM ( SELECT @var3:=12, sq4_alias1.*
 FROM t1 AS sq4_alias1
@@ -6156,7 +6156,7 @@ FROM t2 AS c_sq1_alias1
 WHERE (c_sq1_alias1.col_int_nokey != @var2
 OR c_sq1_alias1.pk != @var3)) ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 3	DEPENDENT SUBQUERY	c_sq1_alias1	system	PRIMARY	NULL	NULL	NULL	1	
 SELECT * FROM ( SELECT sq4_alias1.*
 FROM t1 AS sq4_alias1

mysql-test/r/subselect_no_opts.result

@@ -13,7 +13,7 @@ select (select 2);
 2
 explain extended select (select 2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select 2 AS `(select 2)`
@@ -737,7 +737,7 @@ id
 1
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using index
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select `test`.`t2`.`id` AS `id` from `test`.`t2` where (`test`.`t2`.`id` = 1)
@@ -749,7 +749,7 @@ id
 2
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using where; Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using where; Using index
 Warnings:
 Note	1249	Select 3 was reduced during optimization
 Note	1249	Select 2 was reduced during optimization
@@ -883,7 +883,7 @@ select 10.5 > ANY (SELECT * from t1);
 1
 explain extended select (select a+1) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
 Note	1249	Select 2 was reduced during optimization
@@ -4552,7 +4552,7 @@ int_nokey	int_key
 0	0
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
+1	SIMPLE	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
 DROP TABLE C;
 # End of test for bug#45061.
 #
@@ -6107,7 +6107,7 @@ FROM t1 AS sq4_alias1
 WHERE (sq4_alias1.col_varchar_key + NULL) IS NULL OR
 sq4_alias1.col_varchar_key = @var3 ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
 2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
 SELECT * FROM ( SELECT @var3:=12, sq4_alias1.*
 FROM t1 AS sq4_alias1
@@ -6152,7 +6152,7 @@ FROM t2 AS c_sq1_alias1
 WHERE (c_sq1_alias1.col_int_nokey != @var2
 OR c_sq1_alias1.pk != @var3)) ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 3	DEPENDENT SUBQUERY	c_sq1_alias1	system	PRIMARY	NULL	NULL	NULL	1	
 SELECT * FROM ( SELECT sq4_alias1.*
 FROM t1 AS sq4_alias1

mysql-test/r/subselect_no_scache.result

@@ -16,7 +16,7 @@ select (select 2);
 2
 explain extended select (select 2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select 2 AS `(select 2)`
@@ -740,7 +740,7 @@ id
 1
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using index
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select `test`.`t2`.`id` AS `id` from `test`.`t2` where (`test`.`t2`.`id` = 1)
@@ -752,7 +752,7 @@ id
 2
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using where; Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using where; Using index
 Warnings:
 Note	1249	Select 3 was reduced during optimization
 Note	1249	Select 2 was reduced during optimization
@@ -886,7 +886,7 @@ select 10.5 > ANY (SELECT * from t1);
 1
 explain extended select (select a+1) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
 Note	1249	Select 2 was reduced during optimization
@@ -4560,7 +4560,7 @@ int_nokey	int_key
 0	0
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
+1	SIMPLE	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
 DROP TABLE C;
 # End of test for bug#45061.
 #
@@ -6118,7 +6118,7 @@ FROM t1 AS sq4_alias1
 WHERE (sq4_alias1.col_varchar_key + NULL) IS NULL OR
 sq4_alias1.col_varchar_key = @var3 ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
 2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
 SELECT * FROM ( SELECT @var3:=12, sq4_alias1.*
 FROM t1 AS sq4_alias1
@@ -6163,7 +6163,7 @@ FROM t2 AS c_sq1_alias1
 WHERE (c_sq1_alias1.col_int_nokey != @var2
 OR c_sq1_alias1.pk != @var3)) ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 3	DEPENDENT SUBQUERY	c_sq1_alias1	system	PRIMARY	NULL	NULL	NULL	1	
 SELECT * FROM ( SELECT sq4_alias1.*
 FROM t1 AS sq4_alias1

mysql-test/r/subselect_no_semijoin.result

@@ -13,7 +13,7 @@ select (select 2);
 2
 explain extended select (select 2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select 2 AS `(select 2)`
@@ -737,7 +737,7 @@ id
 1
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using index
 Warnings:
 Note	1249	Select 2 was reduced during optimization
 Note	1003	select `test`.`t2`.`id` AS `id` from `test`.`t2` where (`test`.`t2`.`id` = 1)
@@ -749,7 +749,7 @@ id
 2
 EXPLAIN EXTENDED SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ref	id	id	5	const	1	100.00	Using where; Using index
+1	SIMPLE	t2	ref	id	id	5	const	1	100.00	Using where; Using index
 Warnings:
 Note	1249	Select 3 was reduced during optimization
 Note	1249	Select 2 was reduced during optimization
@@ -883,7 +883,7 @@ select 10.5 > ANY (SELECT * from t1);
 1
 explain extended select (select a+1) from t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
 Note	1249	Select 2 was reduced during optimization
@@ -4552,7 +4552,7 @@ int_nokey	int_key
 0	0
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
+1	SIMPLE	C	ALL	NULL	NULL	NULL	NULL	20	100.00	Using where
 DROP TABLE C;
 # End of test for bug#45061.
 #
@@ -6107,7 +6107,7 @@ FROM t1 AS sq4_alias1
 WHERE (sq4_alias1.col_varchar_key + NULL) IS NULL OR
 sq4_alias1.col_varchar_key = @var3 ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	0	const row not found
 2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
 SELECT * FROM ( SELECT @var3:=12, sq4_alias1.*
 FROM t1 AS sq4_alias1
@@ -6152,7 +6152,7 @@ FROM t2 AS c_sq1_alias1
 WHERE (c_sq1_alias1.col_int_nokey != @var2
 OR c_sq1_alias1.pk != @var3)) ) AS alias3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 3	DEPENDENT SUBQUERY	c_sq1_alias1	system	PRIMARY	NULL	NULL	NULL	1	
 SELECT * FROM ( SELECT sq4_alias1.*
 FROM t1 AS sq4_alias1

mysql-test/r/subselect_sj.result

@@ -941,9 +941,9 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
 EXECUTE stmt;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	PRIMARY	PRIMARY	4	NULL	2	Using index
+1	PRIMARY	t1	index	PRIMARY	PRIMARY	4	NULL	2	Using index
-1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
+1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
+1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
 DROP TABLE t1, t2, t3;
 DROP VIEW v2, v3;
 # End of Bug#49198

mysql-test/r/subselect_sj_jcl6.result

@@ -954,9 +954,9 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
 EXECUTE stmt;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	PRIMARY	PRIMARY	4	NULL	2	Using index
+1	PRIMARY	t1	index	PRIMARY	PRIMARY	4	NULL	2	Using index
-1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
+1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
+1	PRIMARY	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.t1field	1	Using index
 DROP TABLE t1, t2, t3;
 DROP VIEW v2, v3;
 # End of Bug#49198

mysql-test/r/table_elim.result

@@ -119,27 +119,27 @@ t2 where id=f.id);
 This should use one table:
 explain select id from v1 where id=2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	f	const	PRIMARY	PRIMARY	4	const	1	Using index
+1	PRIMARY	f	const	PRIMARY	PRIMARY	4	const	1	Using index
 This should use one table:
 explain extended select id from v1 where id in (1,2,3,4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	f	range	PRIMARY	PRIMARY	4	NULL	4	100.00	Using where; Using index
+1	PRIMARY	f	range	PRIMARY	PRIMARY	4	NULL	4	100.00	Using where; Using index
 Warnings:
 Note	1276	Field or reference 'test.a2.id' of SELECT #3 was resolved in SELECT #2
 Note	1003	select `f`.`id` AS `id` from `test`.`t0` `f` where (`f`.`id` in (1,2,3,4))
 This should use facts and a1 tables:
 explain extended select id from v1 where attr1 between 12 and 14;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	a1	range	PRIMARY,attr1	attr1	5	NULL	2	100.00	Using index condition
+1	PRIMARY	a1	range	PRIMARY,attr1	attr1	5	NULL	2	100.00	Using index condition
-1	SIMPLE	f	eq_ref	PRIMARY	PRIMARY	4	test.a1.id	1	100.00	Using index
+1	PRIMARY	f	eq_ref	PRIMARY	PRIMARY	4	test.a1.id	1	100.00	Using index
 Warnings:
 Note	1276	Field or reference 'test.a2.id' of SELECT #3 was resolved in SELECT #2
 Note	1003	select `f`.`id` AS `id` from `test`.`t0` `f` join `test`.`t1` `a1` where ((`f`.`id` = `a1`.`id`) and (`a1`.`attr1` between 12 and 14))
 This should use facts, a2 and its subquery:
 explain extended select id from v1 where attr2 between 12 and 14;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	a2	range	PRIMARY,attr2	attr2	5	NULL	5	100.00	Using index condition; Using where
+1	PRIMARY	a2	range	PRIMARY,attr2	attr2	5	NULL	5	100.00	Using index condition; Using where
-1	SIMPLE	f	eq_ref	PRIMARY	PRIMARY	4	test.a2.id	1	100.00	Using index
+1	PRIMARY	f	eq_ref	PRIMARY	PRIMARY	4	test.a2.id	1	100.00	Using index
 3	DEPENDENT SUBQUERY	t2	ref	PRIMARY	PRIMARY	4	test.a2.id	2	100.00	Using index
 Warnings:
 Note	1276	Field or reference 'test.a2.id' of SELECT #3 was resolved in SELECT #2
@@ -147,27 +147,27 @@ Note	1003	select `f`.`id` AS `id` from `test`.`t0` `f` join `test`.`t2` `a2` whe
 This should use one table:
 explain select id from v2 where id=2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	f	const	PRIMARY	PRIMARY	4	const	1	Using index
+1	PRIMARY	f	const	PRIMARY	PRIMARY	4	const	1	Using index
 This should use one table:
 explain extended select id from v2 where id in (1,2,3,4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	f	range	PRIMARY	PRIMARY	4	NULL	4	100.00	Using where; Using index
+1	PRIMARY	f	range	PRIMARY	PRIMARY	4	NULL	4	100.00	Using where; Using index
 Warnings:
 Note	1276	Field or reference 'test.f.id' of SELECT #3 was resolved in SELECT #2
 Note	1003	select `f`.`id` AS `id` from `test`.`t0` `f` where (`f`.`id` in (1,2,3,4))
 This should use facts and a1 tables:
 explain extended select id from v2 where attr1 between 12 and 14;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	a1	range	PRIMARY,attr1	attr1	5	NULL	2	100.00	Using index condition
+1	PRIMARY	a1	range	PRIMARY,attr1	attr1	5	NULL	2	100.00	Using index condition
-1	SIMPLE	f	eq_ref	PRIMARY	PRIMARY	4	test.a1.id	1	100.00	Using index
+1	PRIMARY	f	eq_ref	PRIMARY	PRIMARY	4	test.a1.id	1	100.00	Using index
 Warnings:
 Note	1276	Field or reference 'test.f.id' of SELECT #3 was resolved in SELECT #2
 Note	1003	select `f`.`id` AS `id` from `test`.`t0` `f` join `test`.`t1` `a1` where ((`f`.`id` = `a1`.`id`) and (`a1`.`attr1` between 12 and 14))
 This should use facts, a2 and its subquery:
 explain extended select id from v2 where attr2 between 12 and 14;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	a2	range	PRIMARY,attr2	attr2	5	NULL	5	100.00	Using index condition
+1	PRIMARY	a2	range	PRIMARY,attr2	attr2	5	NULL	5	100.00	Using index condition
-1	SIMPLE	f	eq_ref	PRIMARY	PRIMARY	4	test.a2.id	1	100.00	Using where; Using index
+1	PRIMARY	f	eq_ref	PRIMARY	PRIMARY	4	test.a2.id	1	100.00	Using where; Using index
 3	DEPENDENT SUBQUERY	t2	ref	PRIMARY	PRIMARY	4	test.f.id	2	100.00	Using index
 Warnings:
 Note	1276	Field or reference 'test.f.id' of SELECT #3 was resolved in SELECT #2

mysql-test/r/view.result

@@ -119,7 +119,7 @@ c
 12
 explain extended select c from v5;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	<derived3>	ALL	NULL	NULL	NULL	NULL	5	100.00	
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	5	100.00	
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	
 Warnings:
 Note	1003	select (`v2`.`c` + 1) AS `c` from `test`.`v2`
@@ -4475,8 +4475,8 @@ f1	f1
 1	1
 EXPLAIN EXTENDED SELECT * FROM v2 AS a1, v2 AS a2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	<derived3>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using temporary; Using filesort
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using temporary; Using filesort
-1	SIMPLE	<derived5>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using join buffer (flat, BNL join)
+1	PRIMARY	<derived5>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using join buffer (flat, BNL join)
 5	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
 Warnings:

mysql-test/t/explain_non_select.test

@@ -0,0 +1,86 @@
+#
+# MariaDB tests for EXPLAIN UPDATE/DELETE.
+#
+--disable_warnings
+drop table if exists t0, t1;
+--enable_warnings
+
+create table t0 (a int) engine=myisam;
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+
+--echo #
+--echo #  Tests for single-table DELETE
+--echo # 
+
+explain select * from t0 where a=3;
+explain delete from t0 where a=3;
+
+--echo # DELETE without WHERE is a special case:
+explain delete from t0;
+
+create table t1 (a int, b int, filler char(100), key(a), key(b));
+insert into t1 
+select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler' 
+from t0 A, t0 B, t0 C;
+
+--echo # This should use an index,  possible_keys=NULL because there is no WHERE
+explain delete from t1 order by a limit 2;
+
+--echo # This should use range, possible_keys={a,b}
+explain delete from t1 where a<20 and b < 10;
+
+--echo # This should use ALL + filesort
+explain delete from t1 order by a+1 limit 2;
+
+--echo # This should use range + using filesort
+explain delete from t1 where a<20 order by b limit 2;
+
+--echo # Try some subqueries:
+explain delete from t1 where a < (select max(a) from t0);
+explain delete from t1 where a < (select max(a) from t0 where a < t1.b);
+
+--echo #
+--echo #  Tests for multi-table DELETE
+--echo # 
+explain delete t1 from t0, t1 where t0.a = t1.a;
+drop table t0, t1;
+
+--echo # ###################################################################
+--echo # ## EXPLAIN UPDATE tests
+--echo # ###################################################################
+create table t0 (a int) engine=myisam;
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+
+explain update t0 set a=3 where a=4;
+
+create table t1 (a int, b int, filler char(100), key(a), key(b));
+insert into t1 
+select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler' 
+from t0 A, t0 B, t0 C;
+
+explain update t1 set a=a+1 where 3>4;
+explain update t1 set a=a+1 where a=3 and a=4;
+
+--echo # This should use an index,  possible_keys=NULL because there is no WHERE
+explain update t1 set a=a+1 order by a limit 2;
+
+--echo # This should use range, possible_keys={a,b}
+explain update t1 set filler='fooo' where a<20 and b < 10;
+
+--echo # This should use ALL + filesort
+explain update t1 set filler='fooo' order by a+1 limit 2;
+
+--echo # This should use range + using filesort
+explain update t1 set filler='fooo' where a<20 order by b limit 2;
+
+--echo # Try some subqueries:
+explain update t1 set filler='fooo' where a < (select max(a) from t0);
+explain update t1 set filler='fooo' where a < (select max(a) from t0 where a < t1.b);
+
+--echo #
+--echo #  Tests for multi-table UPDATE
+--echo # 
+explain update t0, t1 set t1.a=t1.a+1 where t0.a = t1.a;
+
+
+drop table t0, t1;

mysql-test/t/show_explain.test

@@ -202,7 +202,6 @@ set debug_dbug='+d,show_explain_probe_join_exec_end';
 send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
 connection default;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;
@@ -238,10 +237,10 @@ set debug_dbug='+d,show_explain_probe_join_exec_start';
 send update t2 set dummy=0 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
 connection default;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+#--error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+#--error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;
@@ -249,7 +248,7 @@ drop table t2;
 set debug_dbug=@old_debug;
 
 --echo #
---echo # Attempt SHOW EXPLAIN for a DELETE
+--echo # Attempt SHOW EXPLAIN for a DELETE (UPD: now works)
 --echo # 
 create table t2 as select a as a, a as dummy from t0 limit 2;
 set @show_explain_probe_select_id=2;
@@ -257,10 +256,10 @@ set debug_dbug='+d,show_explain_probe_join_exec_start';
 send delete from t2 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
 connection default;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+#--error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+#--error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;
@@ -349,7 +348,7 @@ connection default;
 --source include/wait_condition.inc
 --echo # FIXED by "conservative assumptions about when QEP is available" fix:
 --echo #    NOTE: current code will not show "Using join buffer": 
---error ER_TARGET_NOT_EXPLAINABLE
+#--error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;
@@ -428,7 +427,7 @@ set debug_dbug='+d,show_explain_probe_join_exec_end';
 send select * from t0 where 1>10;
 connection default;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+#--error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;
@@ -444,7 +443,7 @@ set debug_dbug='+d,show_explain_probe_join_exec_end';
 send select * from t0,t3 where t3.a=112233;
 connection default;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+# --error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;
@@ -540,7 +539,7 @@ send
   SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`);
 connection default;
 --source include/wait_condition.inc
---error ER_TARGET_NOT_EXPLAINABLE
+# --error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
 connection con1;
 reap;

mysql-test/t/show_explain_non_select.test

@@ -0,0 +1,78 @@
+#
+# SHOW EXPLAIN tests for non-select subqueries
+#
+#--source include/have_debug.inc
+#--source include/have_innodb.inc
+#--source include/not_embedded.inc
+
+--disable_warnings
+drop table if exists t0, t1;
+--enable_warnings
+
+SET @old_debug= @@session.debug;
+set debug_sync='RESET';
+
+# 
+# Setup two threads and their ids
+#
+let $thr1=`select connection_id()`;
+connect (con2, localhost, root,,);
+connection con2;
+let $thr2=`select connection_id()`;
+connection default;
+
+# 
+# Create tables
+# 
+create table t0 (a int) engine=myisam;
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+
+create table t1 (a int, b int, filler char(100), key(a), key(b));
+insert into t1 
+select A.a+10*B.a + 10*C.a, A.a+10*B.a + 10*C.a, 'filler' 
+from t0 A, t0 B, t0 C;
+
+let $wait_condition= select State='show_explain_trap' from information_schema.processlist where id=$thr2;
+
+--echo #
+--echo # Test SHOW EXPLAIN for single-table DELETE
+--echo #
+connection con2;
+set debug_dbug='+d,show_explain_probe_delete_exec_start';
+send delete from t1 where a<10 and b+1>1000;
+
+connection default;
+--source include/wait_condition.inc
+evalp show explain for $thr2;
+connection con2;
+reap;
+
+--echo #
+--echo # Test SHOW EXPLAIN for multi-table DELETE
+--echo #
+set @show_explain_probe_select_id=1;
+set debug_dbug='+d,show_explain_probe_do_select';
+send delete t1 from t1, t0 where t0.a=t1.a and t1.b +1 > 1000;
+connection default;
+--source include/wait_condition.inc
+evalp show explain for $thr2;
+connection con2;
+reap;
+
+--echo #
+--echo # Test SHOW EXPLAIN for single-table UPDATE
+--echo #
+connection con2;
+set debug_dbug='+d,show_explain_probe_update_exec_start';
+send update t1 set filler='filler-data-2' where a<10 and b+1>1000;
+
+connection default;
+--source include/wait_condition.inc
+evalp show explain for $thr2;
+connection con2;
+reap;
+
+drop table t0,t1;
+
+set debug_dbug=@old_debug;
+set debug_sync='RESET';

sql/CMakeLists.txt

@@ -80,6 +80,7 @@ SET (SQL_SOURCE
                sql_reload.cc
 
                # added in MariaDB:
+               opt_qpf.h opt_qpf.cc
                sql_lifo_buffer.h sql_join_cache.h sql_join_cache.cc
                create_options.cc multi_range_read.cc
                opt_index_cond_pushdown.cc opt_subselect.cc

sql/log_event.cc

@@ -9151,6 +9151,7 @@ int Rows_log_event::do_apply_event(Relay_log_info const *rli)
       call might reset the value of current_stmt_binlog_format, so
       we need to do any changes to that value after this function.
     */
+    delete_qpf_query(thd->lex);
     lex_start(thd);
     mysql_reset_thd_for_next_command(thd, 0);
     /*

sql/my_apc.cc

@@ -70,6 +70,7 @@ void Apc_target::enable()
 void Apc_target::disable()
 {
   bool process= FALSE;
+  DBUG_ASSERT(enabled);
   mysql_mutex_lock(LOCK_thd_data_ptr);
   if (!(--enabled))
     process= TRUE;

sql/my_apc.h

@@ -65,6 +65,8 @@ public:
     return test(apc_calls);
   }
 
+  inline bool is_enabled() { return enabled; }
+  
   /* Functor class for calls you can schedule */
   class Apc_call
   {

sql/opt_qpf.cc

@@ -0,0 +1,615 @@
+/*
+   TODO MP AB copyright
+*/
+
+#ifdef USE_PRAGMA_IMPLEMENTATION
+#pragma implementation				// gcc: Class implementation
+#endif
+
+#include "sql_priv.h"
+#include "sql_select.h"
+
+
+QPF_query::QPF_query()
+{
+  upd_del_plan= NULL;
+  operations= 0;
+  //memset(&unions, 0, sizeof(unions));
+  //memset(&selects, 0, sizeof(selects));
+}
+
+
+QPF_query::~QPF_query()
+{
+  delete upd_del_plan;
+  uint i;
+  for (i= 0 ; i < unions.elements(); i++)
+    delete unions.at(i);
+  for (i= 0 ; i < selects.elements(); i++)
+    delete selects.at(i);
+}
+
+
+QPF_node *QPF_query::get_node(uint select_id)
+{
+  QPF_union *u;
+  if ((u= get_union(select_id)))
+    return u;
+  else
+    return get_select(select_id);
+}
+
+QPF_union *QPF_query::get_union(uint select_id)
+{
+  return (unions.elements() > select_id) ? unions.at(select_id) : NULL;
+}
+
+QPF_select *QPF_query::get_select(uint select_id)
+{
+  return (selects.elements() > select_id) ? selects.at(select_id) : NULL;
+}
+
+
+void QPF_query::add_node(QPF_node *node)
+{
+  operations++;
+  if (node->get_type() == QPF_node::QPF_UNION)
+  {
+    QPF_union *u= (QPF_union*)node;
+    uint select_id= u->get_select_id();
+    if (unions.elements() <= select_id)
+      unions.resize(max(select_id+1, unions.elements()*2), NULL);
+
+    QPF_union *old_node;
+    if ((old_node= get_union(select_id)))
+      delete old_node;
+
+    unions.at(select_id)= u;
+  }
+  else
+  {
+    QPF_select *sel= (QPF_select*)node;
+    if (sel->select_id == (int)UINT_MAX)
+    {
+      //TODO this is a "fake select" from a UNION.
+      DBUG_ASSERT(0);
+    }
+    else
+    {
+      uint select_id= sel->select_id;
+      QPF_select *old_node;
+      //DBUG_ASSERT(!get_select(select_id));
+      if (selects.elements() <= select_id)
+        selects.resize(max(select_id+1, selects.elements()*2), NULL);
+
+      if ((old_node= get_select(select_id)))
+        delete old_node;
+
+      selects.at(select_id)= sel;
+    }
+  }
+}
+
+
+/*
+  The main entry point to print EXPLAIN of the entire query
+*/
+
+int QPF_query::print_explain(select_result_sink *output, 
+                             uint8 explain_flags)
+{
+  if (upd_del_plan)
+  {
+    upd_del_plan->print_explain(this, output, explain_flags);
+    return 0;
+  }
+  else
+  {
+    // Start with id=1
+    QPF_node *node= get_node(1);
+    return node->print_explain(this, output, explain_flags);
+  }
+}
+
+
+void QPF_union::push_table_name(List<Item> *item_list)
+{
+}
+
+
+static void push_str(List<Item> *item_list, const char *str)
+{
+  item_list->push_back(new Item_string(str,
+                                      strlen(str), system_charset_info));
+}
+
+
+static void push_string(List<Item> *item_list, String *str)
+{
+  item_list->push_back(new Item_string(str->ptr(), str->length(),
+                       system_charset_info));
+}
+
+
+int QPF_union::print_explain(QPF_query *query, select_result_sink *output, 
+                             uint8 explain_flags)
+{
+  // print all children, in order
+  for (int i= 0; i < (int) union_members.elements(); i++)
+  {
+    QPF_select *sel= query->get_select(union_members.at(i));
+    sel->print_explain(query, output, explain_flags);
+  }
+
+  /* Print a line with "UNION RESULT" */
+  List<Item> item_list;
+  Item *item_null= new Item_null();
+
+  /* `id` column */
+  item_list.push_back(item_null);
+
+  /* `select_type` column */
+  push_str(&item_list, fake_select_type);
+
+  /* `table` column: something like "<union1,2>" */
+  //
+  {
+    char table_name_buffer[SAFE_NAME_LEN];
+    uint childno= 0;
+    uint len= 6, lastop= 0;
+    memcpy(table_name_buffer, STRING_WITH_LEN("<union"));
+
+    for (; childno < union_members.elements() && len + lastop + 5 < NAME_LEN;
+         childno++)
+    {
+      len+= lastop;
+      lastop= my_snprintf(table_name_buffer + len, NAME_LEN - len,
+                          "%u,", union_members.at(childno));
+    }
+
+    if (childno < union_members.elements() || len + lastop >= NAME_LEN)
+    {
+      memcpy(table_name_buffer + len, STRING_WITH_LEN("...>") + 1);
+      len+= 4;
+    }
+    else
+    {
+      len+= lastop;
+      table_name_buffer[len - 1]= '>';  // change ',' to '>'
+    }
+    const CHARSET_INFO *cs= system_charset_info;
+    item_list.push_back(new Item_string(table_name_buffer, len, cs));
+  }
+  //
+  push_table_name(&item_list);
+  
+  /* `partitions` column */
+  if (explain_flags & DESCRIBE_PARTITIONS)
+    item_list.push_back(item_null);
+
+  /* `type` column */
+  push_str(&item_list, join_type_str[JT_ALL]);
+
+  /* `possible_keys` column */
+  item_list.push_back(item_null);
+
+  /* `key` */
+  item_list.push_back(item_null);
+
+  /* `key_len` */
+  item_list.push_back(item_null);
+
+  /* `ref` */
+  item_list.push_back(item_null);
+ 
+  /* `rows` */
+  item_list.push_back(item_null);
+
+  /* `filtered` */
+  if (explain_flags & DESCRIBE_EXTENDED)
+    item_list.push_back(item_null);
+
+  /* `Extra` */
+  StringBuffer<256> extra_buf;
+  if (using_filesort)
+  {
+    extra_buf.append(STRING_WITH_LEN("Using filesort"));
+  }
+  const CHARSET_INFO *cs= system_charset_info;
+  item_list.push_back(new Item_string(extra_buf.ptr(), extra_buf.length(), cs));
+
+  //output->unit.offset_limit_cnt= 0; 
+  if (output->send_data(item_list))
+    return 1;
+
+  return print_explain_for_children(query, output, explain_flags);
+}
+
+
+int QPF_node::print_explain_for_children(QPF_query *query, 
+                                         select_result_sink *output,
+                                         uint8 explain_flags)
+{
+  for (int i= 0; i < (int) children.elements(); i++)
+  {
+    QPF_node *node= query->get_node(children.at(i));
+    if (node->print_explain(query, output, explain_flags))
+      return 1;
+  }
+  return 0;
+}
+
+
+QPF_select::~QPF_select()
+{
+  if (join_tabs)
+  {
+    for (uint i= 0; i< n_join_tabs; i++)
+      delete join_tabs[i];
+    my_free(join_tabs);
+  }
+} 
+
+
+int QPF_select::print_explain(QPF_query *query, select_result_sink *output,
+                              uint8 explain_flags)
+{
+  //output->unit.offset_limit_cnt= 0; 
+
+  if (message)
+  {
+    List<Item> item_list;
+    const CHARSET_INFO *cs= system_charset_info;
+    Item *item_null= new Item_null();
+
+    item_list.push_back(new Item_int((int32) select_id));
+    item_list.push_back(new Item_string(select_type,
+                                        strlen(select_type), cs));
+    for (uint i=0 ; i < 7; i++)
+      item_list.push_back(item_null);
+    if (explain_flags & DESCRIBE_PARTITIONS)
+      item_list.push_back(item_null);
+    if (explain_flags & DESCRIBE_EXTENDED)
+      item_list.push_back(item_null);
+
+    item_list.push_back(new Item_string(message,strlen(message),cs));
+
+    if (output->send_data(item_list))
+      return 1;
+  }
+  else
+  {
+    bool using_tmp= using_temporary;
+    bool using_fs= using_filesort;
+    for (uint i=0; i< n_join_tabs; i++)
+    {
+      join_tabs[i]->print_explain(output, explain_flags, select_id,
+                                  select_type, using_tmp, using_fs);
+      if (i == 0)
+      {
+        /* 
+          "Using temporary; Using filesort" should only be shown near the 1st
+          table
+        */
+        using_tmp= false;
+        using_fs= false;
+      }
+    }
+  }
+
+  return print_explain_for_children(query, output, explain_flags);
+}
+
+
+int QPF_table_access::print_explain(select_result_sink *output, uint8 explain_flags, 
+                                    uint select_id, const char *select_type,
+                                    bool using_temporary, bool using_filesort)
+{
+  List<Item> item_list;
+  Item *item_null= new Item_null();
+  //const CHARSET_INFO *cs= system_charset_info;
+  
+  if (sjm_nest_select_id)
+    select_id= sjm_nest_select_id;
+
+  /* `id` column */
+  item_list.push_back(new Item_int((int32) select_id));
+
+  /* `select_type` column */
+  if (sjm_nest_select_id)
+    push_str(&item_list, "MATERIALIZED");
+  else
+    push_str(&item_list, select_type);
+
+  /* `table` column */
+  push_string(&item_list, &table_name);
+  
+  /* `partitions` column */
+  if (explain_flags & DESCRIBE_PARTITIONS)
+  {
+    if (used_partitions_set)
+    {
+      push_string(&item_list, &used_partitions);
+    }
+    else
+      item_list.push_back(item_null); 
+  }
+
+  /* `type` column */
+  push_str(&item_list, join_type_str[type]);
+
+  /* `possible_keys` column */
+  if (possible_keys_str.length() > 0)
+    push_string(&item_list, &possible_keys_str);
+  else
+    item_list.push_back(item_null); 
+
+  /* `key` */
+  if (key_set)
+    push_string(&item_list, &key);
+  else
+    item_list.push_back(item_null); 
+
+  /* `key_len` */
+  if (key_len_set)
+    push_string(&item_list, &key_len);
+  else
+    item_list.push_back(item_null);
+
+  /* `ref` */
+  if (ref_set)
+    push_string(&item_list, &ref);
+  else
+    item_list.push_back(item_null);
+ 
+  /* `rows` */
+  if (rows_set)
+  {
+    item_list.push_back(new Item_int((longlong) (ulonglong) rows, 
+                         MY_INT64_NUM_DECIMAL_DIGITS));
+  }
+  else
+    item_list.push_back(item_null);
+
+  /* `filtered` */
+  if (explain_flags & DESCRIBE_EXTENDED)
+  {
+    if (filtered_set)
+    {
+      item_list.push_back(new Item_float(filtered, 2));
+    }
+    else
+      item_list.push_back(item_null);
+  }
+
+  /* `Extra` */
+  StringBuffer<256> extra_buf;
+  bool first= true;
+  for (int i=0; i < (int)extra_tags.elements(); i++)
+  {
+    if (first)
+      first= false;
+    else
+      extra_buf.append(STRING_WITH_LEN("; "));
+    append_tag_name(&extra_buf, extra_tags.at(i));
+  }
+
+  if (using_temporary)
+  {
+    if (first)
+      first= false;
+    else
+      extra_buf.append(STRING_WITH_LEN("; "));
+    extra_buf.append(STRING_WITH_LEN("Using temporary"));
+  }
+
+  if (using_filesort)
+  {
+    if (first)
+      first= false;
+    else
+      extra_buf.append(STRING_WITH_LEN("; "));
+    extra_buf.append(STRING_WITH_LEN("Using filesort"));
+  }
+
+  const CHARSET_INFO *cs= system_charset_info;
+  item_list.push_back(new Item_string(extra_buf.ptr(), extra_buf.length(), cs));
+
+  if (output->send_data(item_list))
+    return 1;
+
+  return 0;
+}
+
+
+const char * extra_tag_text[]=
+{
+  "ET_none",
+  "Using index condition",
+  "Using index condition(BKA)",
+  "Using ", //special
+  "Range checked for each record (index map: 0x", //special
+  "Using where with pushed condition",
+  "Using where",
+  "Not exists",
+  
+  "Using index",
+  "Full scan on NULL key",
+  "Skip_open_table",
+  "Open_frm_only",
+  "Open_full_table", 
+
+  "Scanned 0 databases",
+  "Scanned 1 database",
+  "Scanned all databases",
+
+  "Using index for group-by", // Special?
+
+  "USING MRR: DONT PRINT ME", // Special!
+
+  "Distinct",
+  "LooseScan",
+  "Start temporary",
+  "End temporary",
+  "FirstMatch", //TODO: also handle special variant!
+
+  "Using join buffer", // Special!,
+
+  "const row not found",
+  "unique row not found",
+  "Impossible ON condition"
+};
+
+
+void QPF_table_access::append_tag_name(String *str, enum Extra_tag tag)
+{
+  switch (tag) {
+    case ET_USING:
+    {
+      // quick select
+      str->append(STRING_WITH_LEN("Using "));
+      str->append(quick_info);
+      break;
+    }
+    case ET_RANGE_CHECKED_FOR_EACH_RECORD:
+    {
+      /* 4 bits per 1 hex digit + terminating '\0' */
+      char buf[MAX_KEY / 4 + 1];
+      str->append(STRING_WITH_LEN("Range checked for each "
+                                   "record (index map: 0x"));
+      str->append(range_checked_map.print(buf));
+      str->append(')');
+      break;
+    }
+    case ET_USING_MRR:
+    {
+      str->append(mrr_type);
+      break;
+    }
+    case ET_USING_JOIN_BUFFER:
+    {
+      str->append(extra_tag_text[tag]);
+
+      str->append(STRING_WITH_LEN(" ("));
+      const char *buffer_type= bka_type.incremental ? "incremental" : "flat";
+      str->append(buffer_type);
+      str->append(STRING_WITH_LEN(", "));
+      str->append(bka_type.join_alg);
+      str->append(STRING_WITH_LEN(" join"));
+      str->append(STRING_WITH_LEN(")"));
+      if (bka_type.mrr_type.length())
+        str->append(bka_type.mrr_type);
+
+      break;
+    }
+    case ET_FIRST_MATCH:
+    {
+      if (firstmatch_table_name.length())
+      {
+        str->append("FirstMatch(");
+        str->append(firstmatch_table_name);
+        str->append(")");
+      }
+      else
+        str->append(extra_tag_text[tag]);
+      break;
+    }
+    case ET_USING_INDEX_FOR_GROUP_BY:
+    {
+      str->append(extra_tag_text[tag]);
+      if (loose_scan_is_scanning)
+        str->append(" (scanning)");
+      break;
+    }
+    default:
+     str->append(extra_tag_text[tag]);
+  }
+}
+
+
+int QPF_delete::print_explain(QPF_query *query, select_result_sink *output, 
+                              uint8 explain_flags)
+{
+  if (deleting_all_rows)
+  {
+    const char *msg= "Deleting all rows";
+    int res= print_explain_message_line(output, explain_flags,
+                                        1 /*select number*/,
+                                        select_type, msg);
+    return res;
+
+  }
+  else
+  {
+    return QPF_update::print_explain(query, output, explain_flags);
+  }
+}
+
+
+int QPF_update::print_explain(QPF_query *query, select_result_sink *output, 
+                              uint8 explain_flags)
+{
+  StringBuffer<64> extra_str;
+  if (impossible_where)
+  {
+    const char *msg= "Impossible where";
+    int res= print_explain_message_line(output, explain_flags,
+                                        1 /*select number*/,
+                                        select_type, msg);
+    return res;
+  }
+
+  if (using_where)
+    extra_str.append(STRING_WITH_LEN("Using where"));
+
+  if (mrr_type.length() != 0)
+  {
+    if (extra_str.length() !=0)
+      extra_str.append(STRING_WITH_LEN("; "));
+    extra_str.append(mrr_type);
+  }
+
+  if (using_filesort)
+  {
+    if (extra_str.length() !=0)
+      extra_str.append(STRING_WITH_LEN("; "));
+    extra_str.append(STRING_WITH_LEN("Using filesort"));
+  }
+
+  /* 
+    Single-table DELETE commands do not do "Using temporary".
+    "Using index condition" is also not possible (which is an unjustified limitation)
+  */
+
+  print_explain_row(output, explain_flags, 
+                    1, /* id */
+                    select_type,
+                    table_name.c_ptr(), 
+                    // partitions,
+                    jtype,
+                    possible_keys_line.length()? possible_keys_line.c_ptr(): NULL,
+                    key_str.length()? key_str.c_ptr() : NULL,
+                    key_len_str.length() ? key_len_str.c_ptr() : NULL,
+                    NULL, /* 'ref' is always NULL in single-table EXPLAIN DELETE */
+                    rows,
+                    extra_str.c_ptr());
+
+  return print_explain_for_children(query, output, explain_flags);
+}
+
+
+void delete_qpf_query(LEX *lex)
+{
+  delete lex->query_plan_footprint;
+  lex->query_plan_footprint= NULL;
+}
+
+
+void create_qpf_query(LEX *lex, MEM_ROOT *mem_root)
+{
+  DBUG_ASSERT(!lex->query_plan_footprint);
+  lex->query_plan_footprint= new QPF_query;
+  DBUG_ASSERT(mem_root == current_thd->mem_root);
+  lex->query_plan_footprint->mem_root= mem_root;
+}
+

sql/opt_qpf.h

@@ -0,0 +1,418 @@
+/**************************************************************************************
+ 
+  Query Plan Footprint (QPF) structures
+
+  These structures
+  - Can be produced in-expensively from query plan.
+  - Store sufficient information to produce either a tabular or a json EXPLAIN
+    output
+  - Have methods that produce a tabular output.
+ 
+*************************************************************************************/
+
+class QPF_query;
+
+/* 
+  A node can be either a SELECT, or a UNION.
+*/
+class QPF_node : public Sql_alloc
+{
+public:
+  enum qpf_node_type {QPF_UNION, QPF_SELECT, QPF_UPDATE, QPF_DELETE };
+  virtual enum qpf_node_type get_type()= 0;
+
+
+  virtual int get_select_id()= 0;
+
+  /* 
+    A node may have children nodes. When a node's QPF (Query Plan Footprint) is
+    created, children nodes may not yet have QPFs.  This is why we store ids.
+  */
+  Dynamic_array<int> children;
+  void add_child(int select_no)
+  {
+    children.append(select_no);
+  }
+
+  virtual int print_explain(QPF_query *query, select_result_sink *output, 
+                            uint8 explain_flags)=0;
+  
+  int print_explain_for_children(QPF_query *query, select_result_sink *output, 
+                                 uint8 explain_flags);
+  virtual ~QPF_node(){}
+};
+
+
+class QPF_table_access;
+
+
+/*
+  Query Plan Footprint of a SELECT.
+  
+  A select can be:
+  1. A degenerate case. In this case, message!=NULL, and it contains a 
+     description of what kind of degenerate case it is (e.g. "Impossible 
+     WHERE").
+  2. a non-degenrate join. In this case, join_tabs describes the join.
+
+  In the non-degenerate case, a SELECT may have a GROUP BY/ORDER BY operation.
+
+  In both cases, the select may have children nodes. class QPF_node provides
+  a way get node's children.
+*/
+
+class QPF_select : public QPF_node
+{
+public:
+  enum qpf_node_type get_type() { return QPF_SELECT; }
+
+  QPF_select() : 
+    message(NULL), join_tabs(NULL),
+    using_temporary(false), using_filesort(false)
+  {}
+  
+  ~QPF_select();
+
+  bool add_table(QPF_table_access *tab)
+  {
+    if (!join_tabs)
+    {
+      join_tabs= (QPF_table_access**) my_malloc(sizeof(QPF_table_access*) *
+                                                MAX_TABLES, MYF(0));
+      n_join_tabs= 0;
+    }
+    join_tabs[n_join_tabs++]= tab;
+    return false;
+  }
+
+public:
+  int select_id;
+  const char *select_type;
+
+  int get_select_id() { return select_id; }
+
+  /*
+    If message != NULL, this is a degenerate join plan, and all subsequent
+    members have no info 
+  */
+  const char *message;
+  
+  /*
+    A flat array of Query Plan Footprints. The order is "just like EXPLAIN
+    would print them".
+  */
+  QPF_table_access** join_tabs;
+  uint n_join_tabs;
+
+  /* Global join attributes. In tabular form, they are printed on the first row */
+  bool using_temporary;
+  bool using_filesort;
+  
+  int print_explain(QPF_query *query, select_result_sink *output, 
+                    uint8 explain_flags);
+};
+
+
+/* 
+  Query Plan Footprint of a UNION.
+
+  A UNION may or may not have "Using filesort".
+*/
+
+class QPF_union : public QPF_node
+{
+public:
+  enum qpf_node_type get_type() { return QPF_UNION; }
+
+  int get_select_id()
+  {
+    DBUG_ASSERT(union_members.elements() > 0);
+    return union_members.at(0);
+  }
+  /*
+    Members of the UNION.  Note: these are different from UNION's "children".
+    Example:
+
+      (select * from t1) union 
+      (select * from t2) order by (select col1 from t3 ...)
+
+    here 
+      - select-from-t1 and select-from-t2 are "union members",
+      - select-from-t3 is the only "child".
+  */
+  Dynamic_array<int> union_members;
+
+  void add_select(int select_no)
+  {
+    union_members.append(select_no);
+  }
+  void push_table_name(List<Item> *item_list);
+  int print_explain(QPF_query *query, select_result_sink *output, 
+                    uint8 explain_flags);
+
+  const char *fake_select_type;
+  bool using_filesort;
+};
+
+class QPF_delete;
+
+
+/*
+  Query Plan Footprint (QPF) for a query (i.e. a statement).
+
+  This should be able to survive when the query plan was deleted. Currently, 
+  we do not intend for it survive until after query's MEM_ROOT is freed. It
+  does surivive freeing of query's items.
+   
+  For reference, the process of post-query cleanup is as follows:
+
+    >dispatch_command
+    | >mysql_parse
+    | |  ...
+    | | lex_end()
+    | |  ...
+    | | >THD::cleanup_after_query
+    | | | ...
+    | | | free_items()
+    | | | ...
+    | | <THD::cleanup_after_query
+    | |
+    | <mysql_parse
+    |
+    | log_slow_statement()
+    | 
+    | free_root()
+    | 
+    >dispatch_command
+  
+  That is, the order of actions is:
+    - free query's Items
+    - write to slow query log 
+    - free query's MEM_ROOT
+    
+*/
+
+class QPF_query : public Sql_alloc
+{
+public:
+  QPF_query();
+  ~QPF_query();
+  /* Add a new node */
+  void add_node(QPF_node *node);
+
+  /* This will return a select, or a union */
+  QPF_node *get_node(uint select_id);
+
+  /* This will return a select (even if there is a union with this id) */
+  QPF_select *get_select(uint select_id);
+  
+  QPF_union *get_union(uint select_id);
+  
+  /* QPF_delete inherits from QPF_update */
+  QPF_update *upd_del_plan;
+
+  /* Produce a tabular EXPLAIN output */
+  int print_explain(select_result_sink *output, uint8 explain_flags);
+  
+  /* If true, at least part of EXPLAIN can be printed */
+  bool have_query_plan() { return upd_del_plan!= NULL || get_node(1) != NULL; }
+  MEM_ROOT *mem_root;
+private:
+  Dynamic_array<QPF_union*> unions;
+  Dynamic_array<QPF_select*> selects;
+  
+  /* 
+    Debugging aid: count how many times add_node() was called. Ideally, it
+    should be one, we currently allow O(1) query plan saves for each
+    select or union.  The goal is not to have O(#rows_in_some_table), which 
+    is unacceptable.
+  */
+  longlong operations;
+};
+
+
+enum Extra_tag
+{
+  ET_none= 0, /* not-a-tag */
+  ET_USING_INDEX_CONDITION,
+  ET_USING_INDEX_CONDITION_BKA,
+  ET_USING, /* For quick selects of various kinds */
+  ET_RANGE_CHECKED_FOR_EACH_RECORD,
+  ET_USING_WHERE_WITH_PUSHED_CONDITION,
+  ET_USING_WHERE,
+  ET_NOT_EXISTS,
+
+  ET_USING_INDEX,
+  ET_FULL_SCAN_ON_NULL_KEY,
+  ET_SKIP_OPEN_TABLE,
+  ET_OPEN_FRM_ONLY,
+  ET_OPEN_FULL_TABLE,
+
+  ET_SCANNED_0_DATABASES,
+  ET_SCANNED_1_DATABASE,
+  ET_SCANNED_ALL_DATABASES,
+
+  ET_USING_INDEX_FOR_GROUP_BY,
+
+  ET_USING_MRR, // does not print "Using mrr". 
+
+  ET_DISTINCT,
+  ET_LOOSESCAN,
+  ET_START_TEMPORARY,
+  ET_END_TEMPORARY,
+  ET_FIRST_MATCH,
+  
+  ET_USING_JOIN_BUFFER,
+
+  ET_CONST_ROW_NOT_FOUND,
+  ET_UNIQUE_ROW_NOT_FOUND,
+  ET_IMPOSSIBLE_ON_CONDITION,
+
+  ET_total
+};
+
+
+typedef struct st_qpf_bka_type
+{
+  bool incremental;
+  const char *join_alg;
+  StringBuffer<64> mrr_type;
+
+} QPF_BKA_TYPE;
+
+
+/*
+  Query Plan Footprint for a JOIN_TAB.
+*/
+class QPF_table_access : public Sql_alloc
+{
+public:
+  void push_extra(enum Extra_tag extra_tag);
+
+  /* Internals */
+public:
+  /* 
+    0 means this tab is not inside SJM nest and should use QPF_select's id
+    other value means the tab is inside an SJM nest.
+  */
+  int sjm_nest_select_id;
+
+  /* id and 'select_type' are cared-of by the parent QPF_select */
+  TABLE *table;
+  StringBuffer<64> table_name;
+
+  enum join_type type;
+
+  StringBuffer<64> used_partitions;
+  bool used_partitions_set;
+
+  key_map possible_keys;
+  StringBuffer<64> possible_keys_str;
+  
+  /* Not used? */
+  uint key_no;
+  uint key_length;
+
+  bool key_set; /* not set means 'NULL' should be printed */
+  StringBuffer<64> key;
+
+  bool key_len_set; /* not set means 'NULL' should be printed */
+  StringBuffer<64> key_len;
+
+  bool ref_set; /* not set means 'NULL' should be printed */
+  StringBuffer<64> ref;
+
+  bool rows_set; /* not set means 'NULL' should be printed */
+  ha_rows rows;
+
+  bool filtered_set; /* not set means 'NULL' should be printed */
+  double filtered;
+
+  /* 
+    Contents of the 'Extra' column. Some are converted into strings, some have
+    parameters, values for which are stored below.
+  */
+  Dynamic_array<enum Extra_tag> extra_tags;
+
+  // Valid if ET_USING tag is present
+  StringBuffer<64> quick_info;
+
+  // Valid if ET_USING_INDEX_FOR_GROUP_BY is present
+  bool loose_scan_is_scanning;
+  
+  // valid with ET_RANGE_CHECKED_FOR_EACH_RECORD
+  key_map range_checked_map;
+
+  // valid with ET_USING_MRR
+  StringBuffer<64> mrr_type;
+
+  // valid with ET_USING_JOIN_BUFFER
+  //StringBuffer<64> join_buffer_type;
+  QPF_BKA_TYPE bka_type;
+  
+  //TABLE *firstmatch_table;
+  StringBuffer<64> firstmatch_table_name;
+
+  int print_explain(select_result_sink *output, uint8 explain_flags, 
+                    uint select_id, const char *select_type,
+                    bool using_temporary, bool using_filesort);
+private:
+  void append_tag_name(String *str, enum Extra_tag tag);
+};
+
+
+/*
+  Query Plan Footprint for single-table UPDATE. 
+  
+  This is similar to QPF_table_access, except that it is more restrictive.
+  Also, it can have UPDATE operation options, but currently there aren't any.
+*/
+
+class QPF_update : public QPF_node
+{
+public:
+  virtual enum qpf_node_type get_type() { return QPF_UPDATE; }
+  virtual int get_select_id() { return 1; /* always root */ }
+
+  const char *select_type;
+
+  bool impossible_where;
+  StringBuffer<64> table_name;
+
+  enum join_type jtype;
+  StringBuffer<128> possible_keys_line;
+  StringBuffer<128> key_str;
+  StringBuffer<128> key_len_str;
+  StringBuffer<64> mrr_type;
+  
+  bool using_where;
+  ha_rows rows;
+
+  bool using_filesort;
+
+  virtual int print_explain(QPF_query *query, select_result_sink *output, 
+                            uint8 explain_flags);
+};
+
+
+/* 
+  Query Plan Footprint for a single-table DELETE.
+*/
+
+class QPF_delete: public QPF_update
+{
+public:
+  /*
+    TRUE means we're going to call handler->delete_all_rows() and not read any
+    rows.
+  */
+  bool deleting_all_rows;
+
+  virtual enum qpf_node_type get_type() { return QPF_DELETE; }
+  virtual int get_select_id() { return 1; /* always root */ }
+
+  virtual int print_explain(QPF_query *query, select_result_sink *output, 
+                            uint8 explain_flags);
+};
+
+

sql/opt_range.h

@@ -944,11 +944,7 @@ public:
   void dbug_dump(int indent, bool verbose);
 #endif
   bool is_agg_distinct() { return have_agg_distinct; }
-  virtual void append_loose_scan_type(String *str) 
+  bool loose_scan_is_scanning() { return is_index_scan; }
-  {
-    if (is_index_scan)
-      str->append(STRING_WITH_LEN(" (scanning)"));
-  }
 };
 
 

sql/sp_head.cc

@@ -2988,6 +2988,7 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
   }
 
   reinit_stmt_before_use(thd, m_lex);
+  // not here, but inside every instr: create_qpf_query(m_lex);
 
   if (open_tables)
     res= instr->exec_open_and_lock_tables(thd, m_lex->query_tables);
@@ -3022,6 +3023,8 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
       thd->mdl_context.release_statement_locks();
   }
   
+  delete_qpf_query(m_lex);
+
   if (m_lex->query_tables_own_last)
   {
     /*
@@ -3228,6 +3231,7 @@ sp_instr_set::execute(THD *thd, uint *nextp)
 int
 sp_instr_set::exec_core(THD *thd, uint *nextp)
 {
+  create_qpf_query(thd->lex, thd->mem_root);
   int res= thd->spcont->set_variable(thd, m_offset, &m_value);
 
   if (res)
@@ -3240,6 +3244,7 @@ sp_instr_set::exec_core(THD *thd, uint *nextp)
       my_error(ER_OUT_OF_RESOURCES, MYF(ME_FATALERROR));
     }
   }
+  delete_qpf_query(thd->lex);
 
   *nextp = m_ip+1;
   return res;

sql/sql_array.h

@@ -106,6 +106,7 @@ public:
 
   Elem& at(size_t idx)
   {
+    DBUG_ASSERT(idx < array.elements);
     return *(((Elem*)array.buffer) + idx);
   }
 
@@ -139,6 +140,23 @@ public:
     array.elements= n;
   }
 
+  bool resize(size_t new_size, Elem default_val)
+  {
+    size_t old_size= elements();
+    if (allocate_dynamic(&array, new_size))
+      return true;
+    
+    if (new_size > old_size)
+    {
+      set_dynamic(&array, (uchar*)&default_val, new_size - 1);
+      /*for (size_t i= old_size; i != new_size; i++)
+      {
+        at(i)= default_val;
+      }*/
+    }
+    return false;
+  }
+
   ~Dynamic_array()
   {
     delete_dynamic(&array);

sql/sql_class.h

@@ -3409,6 +3409,11 @@ public:
   void begin_dataset() {}
 #endif
   virtual void update_used_tables() {}
+
+  void reset_offset_limit()
+  {
+    unit->offset_limit_cnt= 0;
+  }
 };
 
 

sql/sql_delete.cc

@@ -40,6 +40,132 @@
 #include "records.h"                            // init_read_record,
 #include "sql_derived.h"                        // mysql_handle_list_of_derived
                                                 // end_read_record
+
+
+/*
+  @brief
+    Print query plan of a single-table DELETE command
+  
+  @detail
+    This function is used by EXPLAIN DELETE and by SHOW EXPLAIN when it is
+    invoked on a running DELETE statement.
+*/
+
+void Delete_plan::save_query_plan_footprint(QPF_query *query)
+{
+  QPF_delete* qpf= new QPF_delete;
+
+  if (deleting_all_rows)
+  {
+    qpf->deleting_all_rows= true;
+    qpf->select_type= "SIMPLE";
+  }
+  else
+  {
+    qpf->deleting_all_rows= false;
+    Update_plan::save_query_plan_footprint_intern(query, qpf);
+  }
+
+  query->upd_del_plan= qpf;
+}
+
+
+void Update_plan::save_query_plan_footprint(QPF_query *query)
+{
+  QPF_update* qpf= new QPF_update;
+  save_query_plan_footprint_intern(query, qpf);
+  query->upd_del_plan= qpf;
+}
+
+
+void Update_plan::save_query_plan_footprint_intern(QPF_query *query, QPF_update *qpf)
+{
+  qpf->select_type= "SIMPLE";
+  qpf->table_name.append(table->pos_in_table_list->alias);
+  if (impossible_where)
+  {
+    qpf->impossible_where= true;
+    return;
+  }
+  
+  qpf->impossible_where= false;
+
+  select_lex->set_explain_type(TRUE);
+  qpf->select_type= select_lex->type;
+  
+  /* Set jtype */
+  if (select && select->quick)
+  {
+    int quick_type= select->quick->get_type();
+    if ((quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_MERGE) ||
+        (quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_INTERSECT) ||
+        (quick_type == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT) ||
+        (quick_type == QUICK_SELECT_I::QS_TYPE_ROR_UNION))
+      qpf->jtype= JT_INDEX_MERGE;
+    else
+      qpf->jtype= JT_RANGE;
+  }
+  else
+  {
+    if (index == MAX_KEY)
+      qpf->jtype= JT_ALL;
+    else
+      qpf->jtype= JT_NEXT;
+  }
+
+  qpf->using_where= test(select && select->cond);
+  qpf->using_filesort= using_filesort;
+
+  //using_filesort is already set
+  make_possible_keys_line(table, possible_keys, &qpf->possible_keys_line);
+
+  /* Calculate key_len */
+  if (select && select->quick)
+  {
+    select->quick->add_keys_and_lengths(&qpf->key_str, &qpf->key_len_str);
+  }
+  else
+  {
+    if (index != MAX_KEY)
+    {
+      qpf->key_str.append(table->key_info[index].name);
+    }
+    // key_len stays NULL
+  }
+  qpf->rows= select ? select->records : table_rows;
+
+  if (select && select->quick && 
+      select->quick->get_type() == QUICK_SELECT_I::QS_TYPE_RANGE)
+  {
+    explain_append_mrr_info((QUICK_RANGE_SELECT*)select->quick, &qpf->mrr_type);
+  }
+
+  bool skip= updating_a_view;
+  /* Save subquery children */
+  for (SELECT_LEX_UNIT *unit= select_lex->first_inner_unit();
+       unit;
+       unit= unit->next_unit())
+  {
+    if (skip)
+    {
+      skip= false;
+      continue;
+    }
+    /* 
+      Display subqueries only if they are not parts of eliminated WHERE/ON
+      clauses.
+    */
+    if (!(unit->item && unit->item->eliminated))
+      qpf->add_child(unit->first_select()->select_number);
+    
+    //TODO: temporary?:
+    //  A: yes. optimizing children subqueries has caused them to save QPFs,
+    //  automatically.
+    //unit->save_qpf(query);
+  }
+}
+
+
 /**
   Implement DELETE SQL word.
 
@@ -62,13 +188,16 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   bool          const_cond_result;
   ha_rows	deleted= 0;
   bool          reverse= FALSE;
+  bool          err= true;
   ORDER *order= (ORDER *) ((order_list && order_list->elements) ?
                            order_list->first : NULL);
-  uint usable_index= MAX_KEY;
   SELECT_LEX   *select_lex= &thd->lex->select_lex;
   killed_state killed_status= NOT_KILLED;
   THD::enum_binlog_query_type query_type= THD::ROW_QUERY_TYPE;
   bool with_select= !select_lex->item_list.is_empty();
+  Delete_plan query_plan;
+  query_plan.index= MAX_KEY;
+  query_plan.using_filesort= FALSE;
   DBUG_ENTER("mysql_delete");
 
   if (open_and_lock_tables(thd, table_list, TRUE, 0))
@@ -92,6 +221,11 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   }
   thd_proc_info(thd, "init");
   table->map=1;
+  query_plan.select_lex= &thd->lex->select_lex;
+  query_plan.table= table;
+
+  //psergey-todo: Ugly, discuss with Sanja
+  query_plan.updating_a_view= test(table_list->view);
 
   if (mysql_prepare_delete(thd, table_list, select_lex->with_wild,
                                             select_lex->item_list, &conds))
@@ -168,6 +302,11 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
     ha_rows const maybe_deleted= table->file->stats.records;
     DBUG_PRINT("debug", ("Trying to use delete_all_rows()"));
+
+    query_plan.set_delete_all_rows(maybe_deleted);
+    if (thd->lex->describe)
+      goto exit_without_my_ok;
+
     if (!(error=table->file->ha_delete_all_rows()))
     {
       /*
@@ -192,7 +331,12 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     Item::cond_result result;
     conds= remove_eq_conds(thd, conds, &result);
     if (result == Item::COND_FALSE)             // Impossible where
+    {
       limit= 0;
+      query_plan.set_impossible_where();
+      if (thd->lex->describe)
+        goto exit_without_my_ok;
+    }
   }
 
 #ifdef WITH_PARTITION_STORAGE_ENGINE
@@ -200,6 +344,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   {
     free_underlaid_joins(thd, select_lex);
     // No matching record
+    //psergey-explain-todo: No-partitions used EXPLAIN here..
     my_ok(thd, 0);
     DBUG_RETURN(0);
   }
@@ -216,6 +361,10 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     DBUG_RETURN(TRUE);
   if ((select && select->check_quick(thd, safe_update, limit)) || !limit)
   {
+    query_plan.set_impossible_where();
+    if (thd->lex->describe)
+      goto exit_without_my_ok;
+
     delete select;
     free_underlaid_joins(thd, select_lex);
     /* 
@@ -248,26 +397,47 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
 
   if (order)
   {
-    uint         length= 0;
-    SORT_FIELD  *sortorder;
-    ha_rows examined_rows;
-    ha_rows found_rows;
-    
     table->update_const_key_parts(conds);
     order= simple_remove_const(order, conds);
 
-    bool need_sort;
     if (select && select->quick && select->quick->unique_key_range())
     { // Single row select (always "ordered")
-      need_sort= FALSE;
+      query_plan.using_filesort= FALSE;
-      usable_index= MAX_KEY;
+      query_plan.index= MAX_KEY;
     }
     else
-      usable_index= get_index_for_order(order, table, select, limit,
+      query_plan.index= get_index_for_order(order, table, select, limit,
-                                        &need_sort, &reverse);
+                                            &query_plan.using_filesort, 
-    if (need_sort)
+                                            &reverse);
+  }
+
+  query_plan.select= select;
+  query_plan.possible_keys= table->quick_keys;
+  query_plan.table_rows= table->file->stats.records;
+  
+  /*
+    Ok, we have generated a query plan for the DELETE.
+     - if we're running EXPLAIN DELETE, goto produce explain output 
+     - otherwise, execute the query plan
+  */
+  if (thd->lex->describe)
+    goto exit_without_my_ok;
+
+  query_plan.save_query_plan_footprint(thd->lex->query_plan_footprint);
+  thd->apc_target.enable();
+
+  DBUG_EXECUTE_IF("show_explain_probe_delete_exec_start", 
+                  dbug_serve_apcs(thd, 1););
+
+  if (query_plan.using_filesort)
   {
-      DBUG_ASSERT(usable_index == MAX_KEY);
+    ha_rows examined_rows;
+    ha_rows found_rows;
+    uint         length= 0;
+    SORT_FIELD  *sortorder;
+
+    {
+      DBUG_ASSERT(query_plan.index == MAX_KEY);
       table->sort.io_cache= (IO_CACHE *) my_malloc(sizeof(IO_CACHE),
                                                    MYF(MY_FAE | MY_ZEROFILL |
                                                        MY_THREAD_SPECIFIC));
@@ -281,6 +451,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
       {
         delete select;
         free_underlaid_joins(thd, &thd->lex->select_lex);
+        thd->apc_target.disable();
         DBUG_RETURN(TRUE);
       }
       thd->examined_row_count+= examined_rows;
@@ -299,19 +470,21 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   {
     delete select;
     free_underlaid_joins(thd, select_lex);
+    thd->apc_target.disable();
     DBUG_RETURN(TRUE);
   }
-  if (usable_index == MAX_KEY || (select && select->quick))
+  if (query_plan.index == MAX_KEY || (select && select->quick))
   {
     if (init_read_record(&info, thd, table, select, 1, 1, FALSE))
     {
       delete select;
       free_underlaid_joins(thd, select_lex);
+      thd->apc_target.disable();
       DBUG_RETURN(TRUE);
     }
   }
   else
-    init_read_record_idx(&info, thd, table, 1, usable_index, reverse);
+    init_read_record_idx(&info, thd, table, 1, query_plan.index, reverse);
 
   init_ftfuncs(thd, select_lex, 1);
   thd_proc_info(thd, "updating");
@@ -416,6 +589,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   if (options & OPTION_QUICK)
     (void) table->file->extra(HA_EXTRA_NORMAL);
 
+  thd->apc_target.disable();
 cleanup:
   /*
     Invalidate the table in the query cache if something changed. This must
@@ -479,6 +653,28 @@ cleanup:
     DBUG_PRINT("info",("%ld records deleted",(long) deleted));
   }
   DBUG_RETURN(error >= 0 || thd->is_error());
+  
+  /* Special exits */
+exit_without_my_ok:
+  query_plan.save_query_plan_footprint(thd->lex->query_plan_footprint);
+
+  select_send *result;
+  if (!(result= new select_send()))
+    return 1;                               /* purecov: inspected */
+  List<Item> dummy; /* note: looked in 5.6 and they too use a dummy list like this */
+  result->prepare(dummy, &thd->lex->unit);
+  thd->send_explain_fields(result);
+  int err2= thd->lex->query_plan_footprint->print_explain(result, 0 /* explain flags*/);
+
+  if (err2)
+    result->abort_result_set();
+  else
+    result->send_eof();
+  
+  delete select;
+  free_underlaid_joins(thd, select_lex);
+  //table->set_keyread(false);
+  DBUG_RETURN((err || thd->is_error() || thd->killed) ? 1 : 0);
 }
 
 

sql/sql_join_cache.cc

@@ -2568,34 +2568,26 @@ finish:
     none
 */ 
 
-void JOIN_CACHE::print_explain_comment(String *str)
+void JOIN_CACHE::save_qpf(struct st_qpf_bka_type *qpf)
 {
-  str->append(STRING_WITH_LEN(" ("));
+  qpf->incremental= test(prev_cache);
-  const char *buffer_type= prev_cache ? "incremental" : "flat";
-  str->append(buffer_type);
-  str->append(STRING_WITH_LEN(", "));
 
-  const char *join_alg="";
   switch (get_join_alg()) {
   case BNL_JOIN_ALG:
-    join_alg= "BNL";
+    qpf->join_alg= "BNL";
     break;
   case BNLH_JOIN_ALG:
-    join_alg= "BNLH";
+    qpf->join_alg= "BNLH";
     break;
   case BKA_JOIN_ALG:
-    join_alg= "BKA";
+    qpf->join_alg= "BKA";
     break;
   case BKAH_JOIN_ALG:
-    join_alg= "BKAH";
+    qpf->join_alg= "BKAH";
     break;
   default:
     DBUG_ASSERT(0);
   }
-
-  str->append(join_alg);
-  str->append(STRING_WITH_LEN(" join"));
-  str->append(STRING_WITH_LEN(")"));
 }
 
 /**
@@ -2621,18 +2613,17 @@ static void add_mrr_explain_info(String *str, uint mrr_mode, handler *file)
   }
 }
 
-
+void JOIN_CACHE_BKA::save_qpf(struct st_qpf_bka_type *qpf)
-void JOIN_CACHE_BKA::print_explain_comment(String *str)
 {
-  JOIN_CACHE::print_explain_comment(str); 
+  JOIN_CACHE::save_qpf(qpf); 
-  add_mrr_explain_info(str, mrr_mode, join_tab->table->file);
+  add_mrr_explain_info(&qpf->mrr_type, mrr_mode, join_tab->table->file);
 }
 
 
-void JOIN_CACHE_BKAH::print_explain_comment(String *str)
+void JOIN_CACHE_BKAH::save_qpf(struct st_qpf_bka_type *qpf)
 {
-  JOIN_CACHE::print_explain_comment(str); 
+  JOIN_CACHE::save_qpf(qpf); 
-  add_mrr_explain_info(str, mrr_mode, join_tab->table->file);
+  add_mrr_explain_info(&qpf->mrr_type, mrr_mode, join_tab->table->file);
 }
 
 

sql/sql_join_cache.h

@@ -63,6 +63,7 @@ typedef struct st_cache_field {
 
 class JOIN_TAB_SCAN;
 
+struct st_qpf_bka_type;
 
 /*
   JOIN_CACHE is the base class to support the implementations of 
@@ -657,7 +658,7 @@ public:
   enum_nested_loop_state join_records(bool skip_last);
 
   /* Add a comment on the join algorithm employed by the join cache */
-  virtual void print_explain_comment(String *str);
+  virtual void save_qpf(struct st_qpf_bka_type *qpf);
 
   THD *thd();
 
@@ -1335,7 +1336,7 @@ public:
   /* Check index condition of the joined table for a record from BKA cache */
   bool skip_index_tuple(range_id_t range_info);
 
-  void print_explain_comment(String *str);
+  void save_qpf(struct st_qpf_bka_type *qpf);
 };
 
 
@@ -1426,5 +1427,5 @@ public:
   /* Check index condition of the joined table for a record from BKAH cache */
   bool skip_index_tuple(range_id_t range_info);
 
-  void print_explain_comment(String *str);
+  void save_qpf(struct st_qpf_bka_type *qpf);
 };

sql/sql_lex.cc

@@ -448,6 +448,8 @@ void lex_start(THD *thd)
 
   lex->thd= lex->unit.thd= thd;
   
+  lex->query_plan_footprint= NULL;
+
   lex->context_stack.empty();
   lex->unit.init_query();
   lex->unit.init_select();
@@ -2570,7 +2572,8 @@ void Query_tables_list::destroy_query_tables_list()
 */
 
 LEX::LEX()
-  :result(0), option_type(OPT_DEFAULT), is_lex_started(0),
+  : query_plan_footprint(NULL),
+    result(0), option_type(OPT_DEFAULT), is_lex_started(0),
    limit_rows_examined_cnt(ULONGLONG_MAX)
 {
 
@@ -3512,6 +3515,18 @@ bool st_select_lex::optimize_unflattened_subqueries(bool const_only)
         is_correlated_unit|= sl->is_correlated;
         inner_join->select_options= save_options;
         un->thd->lex->current_select= save_select;
+        /// psergey:
+        QPF_query *qpf;
+        if ((qpf= inner_join->thd->lex->query_plan_footprint))
+        {
+          QPF_select *qp_sel;
+          if ((qp_sel= qpf->get_select(inner_join->select_lex->select_number)))
+          {
+            sl->set_explain_type(TRUE);
+            qp_sel->select_type= sl->type;
+          }
+        }
+        ///
         if (empty_union_result)
         {
           /*
@@ -4191,89 +4206,55 @@ bool st_select_lex::is_merged_child_of(st_select_lex *ancestor)
   return all_merged;
 }
 
+/* 
+  This is used by SHOW EXPLAIN. It assuses query plan has been already 
+  collected into QPF structures and we only need to print it out.
+*/
 
-int print_explain_message_line(select_result_sink *result, 
+int LEX::print_explain(select_result_sink *output, uint8 explain_flags,
-                               SELECT_LEX *select_lex,
-                               bool on_the_fly,
-                               uint8 options,
-                               const char *message);
-
-
-int st_select_lex::print_explain(select_result_sink *output, 
-                                 uint8 explain_flags,
                        bool *printed_anything)
 {
   int res;
-  if (join && join->have_query_plan == JOIN::QEP_AVAILABLE)
+  if (query_plan_footprint && query_plan_footprint->have_query_plan())
   {
-    /*
+    res= query_plan_footprint->print_explain(output, explain_flags);
-      There is a number of reasons join can be marked as degenerate, so all
+    *printed_anything= true;
-      three conditions below can happen simultaneously, or individually:
-    */
-    *printed_anything= TRUE;
-    if (!join->table_count || !join->tables_list || join->zero_result_cause)
-    {
-      /* It's a degenerate join */
-      const char *cause= join->zero_result_cause ? join-> zero_result_cause : 
-                                                   "No tables used";
-      res= join->print_explain(output, explain_flags, TRUE, FALSE, FALSE, 
-                               FALSE, cause);
   }
   else
   {
-      res= join->print_explain(output, explain_flags, TRUE,
+    res= 0;
-                               join->need_tmp, // need_tmp_table
+    *printed_anything= false;
-                               !join->skip_sort_order && !join->no_order &&
-                               (join->order || join->group_list), // bool need_order
-                               join->select_distinct, // bool distinct
-                               NULL); //const char *message
   }
-    if (res)
-      goto err;
-
-    for (SELECT_LEX_UNIT *unit= join->select_lex->first_inner_unit();
-         unit;
-         unit= unit->next_unit())
-    {
-      /* 
-        Display subqueries only if they are not parts of eliminated WHERE/ON
-        clauses.
-      */
-      if (!(unit->item && unit->item->eliminated))
-      {
-        if ((res= unit->print_explain(output, explain_flags, printed_anything)))
-          goto err;
-      }
-    }
-  }
-  else
-  {
-    const char *msg;
-    if (!join)
-      DBUG_ASSERT(0); /* Seems not to be possible */
-
-    /* Not printing anything useful, don't touch *printed_anything here */
-    if (join->have_query_plan == JOIN::QEP_NOT_PRESENT_YET)
-      msg= "Not yet optimized";
-    else
-    {
-      DBUG_ASSERT(join->have_query_plan == JOIN::QEP_DELETED);
-      msg= "Query plan already deleted";
-    }
-    res= print_explain_message_line(output, this, TRUE /* on_the_fly */,
-                                    0, msg);
-  }
-err:
   return res;
 }
 
 
-int st_select_lex_unit::print_explain(select_result_sink *output, 
+/*
-                                      uint8 explain_flags, bool *printed_anything)
+  Save query plan of a UNION. The only variable member is whether the union has
-{
+  "Using filesort".
-  int res= 0;
-  SELECT_LEX *first= first_select();
 
+  There is also save_union_qpf_part2() function, which is called before we read
+  UNION's output.
+
+  The reason for it is examples like this:
+
+     SELECT col1 FROM t1 UNION SELECT col2 FROM t2 ORDER BY (select ... from t3 ...)
+
+  Here, the (select ... from t3 ...) subquery must be a child of UNION's
+  st_select_lex. However, it is not connected as child until a very late 
+  stage in execution.
+*/
+
+int st_select_lex_unit::save_union_qpf(QPF_query *output)
+{
+  SELECT_LEX *first= first_select();
+  QPF_union *qpfu= new (output->mem_root) QPF_union;
+
+  /*
+    TODO: The following code should be eliminated. If we have a capability to
+    save Query Plan Footprints, we should just save them, and never need to 
+    print "query plan already deleted".
+  */
   if (first && !first->next_select() && !first->join)
   {
     /*
@@ -4281,24 +4262,44 @@ int st_select_lex_unit::print_explain(select_result_sink *output,
       EXPLAIN state" error.
     */
     const char *msg="Query plan already deleted";
-    res= print_explain_message_line(output, first, TRUE /* on_the_fly */,
+    first->set_explain_type(TRUE/* on_the_fly */);
-                                    0, msg);
+
+    QPF_select *qp_sel= new (output->mem_root)QPF_select;
+    qp_sel->select_id= first->select_number;
+    qp_sel->select_type= first->type;
+    qp_sel->message= msg;
+    output->add_node(qp_sel);
+    qpfu->add_select(qp_sel->select_id);
     return 0;
   }
 
   for (SELECT_LEX *sl= first; sl; sl= sl->next_select())
-  {
+    qpfu->add_select(sl->select_number);
-    if ((res= sl->print_explain(output, explain_flags, printed_anything)))
+
-      break;
+  // Save the UNION node
+  output->add_node(qpfu);
+
+  qpfu->fake_select_type= "UNION RESULT";
+  qpfu->using_filesort= test(global_parameters->order_list.first);
+  return 0;
 }
 
-  /* Note: fake_select_lex->join may be NULL or non-NULL at this point */
+
+int st_select_lex_unit::save_union_qpf_part2(QPF_query *output)
+{
+  QPF_union *qpfu= output->get_union(first_select()->select_number);
   if (fake_select_lex)
   {
-    res= print_fake_select_lex_join(output, TRUE /* on the fly */,
+    for (SELECT_LEX_UNIT *unit= fake_select_lex->first_inner_unit(); 
-                                    fake_select_lex, explain_flags);
+         unit; unit= unit->next_unit())
+    {
+      if (!(unit->item && unit->item->eliminated))
+      {
+        qpfu->add_child(unit->first_select()->select_number);
       }
-  return res;
+    }
+  }
+  return 0;
 }
 
 

sql/sql_lex.h

@@ -618,7 +618,10 @@ class select_result;
 class JOIN;
 class select_union;
 class Procedure;
+class QPF_query;
 
+void delete_qpf_query(LEX *lex);
+void create_qpf_query(LEX *lex, MEM_ROOT *mem_root);
 
 class st_select_lex_unit: public st_select_lex_node {
 protected:
@@ -729,8 +732,9 @@ public:
   friend int subselect_union_engine::exec();
 
   List<Item> *get_unit_column_types();
-  int print_explain(select_result_sink *output, uint8 explain_flags,
+
-                    bool *printed_anything);
+  int save_union_qpf(QPF_query *output);
+  int save_union_qpf_part2(QPF_query *output);
 };
 
 typedef class st_select_lex_unit SELECT_LEX_UNIT;
@@ -1054,8 +1058,7 @@ public:
   bool save_prep_leaf_tables(THD *thd);
 
   bool is_merged_child_of(st_select_lex *ancestor);
-  int print_explain(select_result_sink *output, uint8 explain_flags, 
+
-                    bool *printed_anything);
   /*
     For MODE_ONLY_FULL_GROUP_BY we need to maintain two flags:
      - Non-aggregated fields are used in this select.
@@ -2360,6 +2363,69 @@ protected:
   LEX *m_lex;
 };
 
+
+class Delete_plan;
+class SQL_SELECT;
+
+class QPF_query;
+class QPF_update;
+
+/* 
+  Query plan of a single-table UPDATE.
+  (This is actually a plan for single-table DELETE also)
+*/
+
+class Update_plan
+{
+protected:
+  bool impossible_where;
+public:
+  bool updating_a_view;
+  TABLE *table;
+  SQL_SELECT *select;
+  uint index;
+  ha_rows table_rows; /* Use if select==NULL */
+  /*
+    Top-level select_lex. Most of its fields are not used, we need it only to
+    get to the subqueries.
+  */
+  SELECT_LEX *select_lex;
+  
+  key_map possible_keys;
+  bool using_filesort;
+  
+  /* Set this plan to be a plan to do nothing because of impossible WHRE*/
+  void set_impossible_where() { impossible_where= true; }
+
+  void save_query_plan_footprint(QPF_query *query);
+  void save_query_plan_footprint_intern(QPF_query *query, QPF_update *qpf);
+  virtual ~Update_plan() {}
+
+  Update_plan() : impossible_where(false), using_filesort(false) {}
+};
+
+
+/* Query plan of a single-table DELETE */
+class Delete_plan : public Update_plan
+{
+  bool deleting_all_rows;
+public:
+
+  /* Construction functions */
+  Delete_plan() : 
+    deleting_all_rows(false)  {}
+
+  /* Set this query plan to be a plan to make a call to h->delete_all_rows() */
+  void set_delete_all_rows(ha_rows rows_arg) 
+  { 
+    deleting_all_rows= true;
+    table_rows= rows_arg;
+  }
+
+  void save_query_plan_footprint(QPF_query *query);
+};
+
+
 /* The state of the lex parsing. This is saved in the THD struct */
 
 struct LEX: public Query_tables_list
@@ -2371,6 +2437,9 @@ struct LEX: public Query_tables_list
   /* list of all SELECT_LEX */
   SELECT_LEX *all_selects_list;
   
+  /* Query Plan Footprint of a currently running select  */
+  QPF_query *query_plan_footprint;
+
   char *length,*dec,*change;
   LEX_STRING name;
   char *help_arg;
@@ -2786,6 +2855,9 @@ struct LEX: public Query_tables_list
     }
     return FALSE;
   }
+
+  int print_explain(select_result_sink *output, uint8 explain_flags,
+                    bool *printed_anything);
 };
 
 

sql/sql_parse.cc

@@ -598,6 +598,7 @@ static void handle_bootstrap_impl(THD *thd)
 #if defined(ENABLED_PROFILING)
     thd->profiling.finish_current_query();
 #endif
+    delete_qpf_query(thd->lex);
 
     if (bootstrap_error)
       break;
@@ -807,7 +808,9 @@ bool do_command(THD *thd)
   my_net_set_read_timeout(net, thd->variables.net_read_timeout);
 
   DBUG_ASSERT(packet_length);
+  DBUG_ASSERT(!thd->apc_target.is_enabled());
   return_value= dispatch_command(command, thd, packet+1, (uint) (packet_length-1));
+  DBUG_ASSERT(!thd->apc_target.is_enabled());
 
 out:
   DBUG_RETURN(return_value);
@@ -1117,6 +1120,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       ulong length= (ulong)(packet_end - beginning_of_next_stmt);
 
       log_slow_statement(thd);
+      DBUG_ASSERT(!thd->apc_target.is_enabled());
 
       /* Remove garbage at start of query */
       while (length > 0 && my_isspace(thd->charset(), *beginning_of_next_stmt))
@@ -1489,6 +1493,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
   thd->update_all_stats();
 
   log_slow_statement(thd);
+  /* psergey-todo: this is the place we could print EXPLAIN to slow query log */
 
   thd_proc_info(thd, "cleaning up");
   thd->reset_query();
@@ -1524,6 +1529,8 @@ void log_slow_statement(THD *thd)
 {
   DBUG_ENTER("log_slow_statement");
 
+  delete_qpf_query(thd->lex);
+
   /*
     The following should never be true with our current code base,
     but better to keep this here so we don't accidently try to log a
@@ -1532,6 +1539,7 @@ void log_slow_statement(THD *thd)
   if (unlikely(thd->in_sub_stmt))
     DBUG_VOID_RETURN;                           // Don't set time for sub stmt
 
+
   /* Follow the slow log filter configuration. */ 
   if (!thd->enable_slow_log ||
       (thd->variables.log_slow_filter
@@ -2186,6 +2194,8 @@ mysql_execute_command(THD *thd)
     thd->mdl_context.release_transactional_locks();
   }
   
+  create_qpf_query(thd->lex, thd->mem_root);
+
 #ifndef DBUG_OFF
   if (lex->sql_command != SQLCOM_SET_OPTION)
     DEBUG_SYNC(thd,"before_execute_sql_command");
@@ -3265,7 +3275,8 @@ end_with_restore_list:
   {
     DBUG_ASSERT(first_table == all_tables && first_table != 0);
     TABLE_LIST *aux_tables= thd->lex->auxiliary_table_list.first;
-    multi_delete *del_result;
+    bool explain= test(lex->describe);
+    select_result *result;
 
     if ((res= multi_delete_precheck(thd, all_tables)))
       break;
@@ -3280,15 +3291,37 @@ end_with_restore_list:
     if ((res= open_and_lock_tables(thd, all_tables, TRUE, 0)))
       break;
 
+    if (!explain)
+    {
       MYSQL_MULTI_DELETE_START(thd->query());
+    }
+
     if ((res= mysql_multi_delete_prepare(thd)))
+    {
+      if (!explain)
       {
         MYSQL_MULTI_DELETE_DONE(1, 0);
+      }
       goto error;
     }
 
-    if (!thd->is_fatal_error &&
+    if (!thd->is_fatal_error)
-        (del_result= new multi_delete(aux_tables, lex->table_count)))
+    {
+      if (explain)
+      {
+        result= new select_send();
+        if (thd->send_explain_fields(result))
+        {
+          delete result;
+          result= NULL;
+        }
+        select_lex->set_explain_type(FALSE);
+        //thd->lex->query_plan_footprint= new QPF_query;
+      }
+      else
+        result= new multi_delete(aux_tables, lex->table_count);
+
+      if (result)
       {
         res= mysql_select(thd, &select_lex->ref_pointer_array,
                           select_lex->get_table_list(),
@@ -3300,18 +3333,39 @@ end_with_restore_list:
                           (select_lex->options | thd->variables.option_bits |
                           SELECT_NO_JOIN_CACHE | SELECT_NO_UNLOCK |
                           OPTION_SETUP_TABLES_DONE) & ~OPTION_BUFFER_RESULT,
-			del_result, unit, select_lex);
+                          result, unit, select_lex);
         res|= thd->is_error();
+
+        if (!explain)
+        {
           MYSQL_MULTI_DELETE_DONE(res, del_result->num_deleted());
+        }
+        else
+        {
+          result->reset_offset_limit(); 
+          thd->lex->query_plan_footprint->print_explain(result, thd->lex->describe);
+          //delete thd->lex->query_plan_footprint;
+          //thd->lex->query_plan_footprint= NULL;
+        }
+      
         if (res)
-        del_result->abort_result_set();
+          result->abort_result_set(); /* for both DELETE and EXPLAIN DELETE */
-      delete del_result;
+        else
+        {
+          if (explain)
+            result->send_eof(); 
+        }
+        delete result;
+      }
     }
     else
     {
       res= TRUE;                                // Error
+      if (!explain)
+      {
         MYSQL_MULTI_DELETE_DONE(1, 0);
       }
+    }
     break;
   }
   case SQLCOM_DROP_TABLE:
@@ -4743,8 +4797,14 @@ finish:
     ha_maria::implicit_commit(thd, FALSE);
 #endif
   }
-
   lex->unit.cleanup();
+  //psergey-todo: print EXPLAIN here? After the above JOIN::cleanup calls?
+  // how do we print EXPLAIN extended, then?
+  if (lex->describe)
+  {
+    DBUG_ASSERT(lex->query_plan_footprint);
+    ///..
+  }
   /* Free tables */
   thd_proc_info(thd, "closing tables");
   close_thread_tables(thd);
@@ -4819,7 +4879,25 @@ static bool execute_sqlcom_select(THD *thd, TABLE_LIST *all_tables)
       if (!(result= new select_send()))
         return 1;                               /* purecov: inspected */
       thd->send_explain_fields(result);
+      //thd->lex->query_plan_footprint= new QPF_query;
       res= mysql_explain_union(thd, &thd->lex->unit, result);
+
+      if (!res)
+      {
+        /* 
+          Do like the original select_describe did: remove OFFSET from the
+          top-level LIMIT
+        */        
+        result->reset_offset_limit(); 
+        thd->lex->query_plan_footprint->print_explain(result, thd->lex->describe);
+      }
+      //delete thd->lex->query_plan_footprint;
+      //thd->lex->query_plan_footprint= NULL;
+
+      //psergey-todo: here, produce the EXPLAIN output.
+      //  mysql_explain_union() itself is only responsible for calling
+      //  optimize() for all parts of the query.
+
       /*
         The code which prints the extended description is not robust
         against malformed queries, so skip it if we have an error.

sql/sql_prepare.cc

@@ -2491,6 +2491,7 @@ void reinit_stmt_before_use(THD *thd, LEX *lex)
     object and because of this can be used in different threads.
   */
   lex->thd= thd;
+  DBUG_ASSERT(!lex->query_plan_footprint);
 
   if (lex->empty_field_list_on_rset)
   {
@@ -3930,6 +3931,8 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
 
   if (! cursor)
     cleanup_stmt();
+  //psergey: TODO the "EXECUTE problem" is here
+  delete_qpf_query(thd->lex);
 
   thd->set_statement(&stmt_backup);
   thd->stmt_arena= old_stmt_arena;

sql/sql_select.h

@@ -198,6 +198,12 @@ int rr_sequential(READ_RECORD *info);
 int rr_sequential_and_unpack(READ_RECORD *info);
 
 
+#include "opt_qpf.h"
+
+/**************************************************************************************
+ * New EXPLAIN structures END
+ *************************************************************************************/
+
 class JOIN_CACHE;
 class SJ_TMP_TABLE;
 class JOIN_TAB_RANGE;
@@ -252,7 +258,9 @@ typedef struct st_join_table {
   JOIN_TAB_RANGE *bush_children;
   
   /* Special content for EXPLAIN 'Extra' column or NULL if none */
-  const char	*info;
+  enum Extra_tag info;
+  //const char	*info;
+
   /* 
     Bitmap of TAB_INFO_* bits that encodes special line for EXPLAIN 'Extra'
     column, or 0 if there is no info.
@@ -1328,6 +1336,8 @@ public:
     pre_sort_join_tab= NULL;
     emb_sjm_nest= NULL;
     sjm_lookup_tables= 0;
+
+    exec_qpf_saved= false;
     /* 
       The following is needed because JOIN::cleanup(true) may be called for 
       joins for which JOIN::optimize was aborted with an error before a proper
@@ -1335,6 +1345,7 @@ public:
     */
     table_access_tabs= NULL; 
   }
+  bool exec_qpf_saved;
 
   int prepare(Item ***rref_pointer_array, TABLE_LIST *tables, uint wind_num,
 	      COND *conds, uint og_num, ORDER *order, ORDER *group,
@@ -1460,10 +1471,7 @@ public:
   {
     return (unit->item && unit->item->is_in_predicate());
   }
-
+  int save_qpf(QPF_query *output, bool need_tmp_table, bool need_order,
-  int print_explain(select_result_sink *result, uint8 explain_flags,
-                     bool on_the_fly,
-                     bool need_tmp_table, bool need_order,
                bool distinct, const char *message);
 private:
   /**
@@ -1834,6 +1842,28 @@ void push_index_cond(JOIN_TAB *tab, uint keyno);
 
 #define OPT_LINK_EQUAL_FIELDS    1
 
+/* EXPLAIN-related utility functions */
+int print_explain_message_line(select_result_sink *result, 
+                               uint8 options,
+                               uint select_number,
+                               const char *select_type,
+                               const char *message);
+void explain_append_mrr_info(QUICK_RANGE_SELECT *quick, String *res);
+int print_explain_row(select_result_sink *result,
+                      uint8 options,
+                      uint select_number,
+                      const char *select_type,
+                      const char *table_name,
+                      //const char *partitions, (todo)
+                      enum join_type jtype,
+                      const char *possible_keys,
+                      const char *index,
+                      const char *key_len,
+                      const char *ref,
+                      ha_rows rows,
+                      const char *extra);
+void make_possible_keys_line(TABLE *table, key_map possible_keys, String *line);
+
 /****************************************************************************
   Temporary table support for SQL Runtime
  ***************************************************************************/

sql/sql_show.cc

@@ -2345,7 +2345,7 @@ void Show_explain_request::call_in_target_thread()
 
   DBUG_ASSERT(current_thd == target_thd);
   set_current_thd(request_thd);
-  if (target_thd->lex->unit.print_explain(explain_buf, 0 /* explain flags*/,
+  if (target_thd->lex->print_explain(explain_buf, 0 /* explain flags*/,
                                      &printed_anything))
   {
     failed_to_produce= TRUE;

sql/sql_string.h

@@ -511,6 +511,38 @@ public:
   }
 };
 
+
+// The following class is a backport from MySQL 5.6:
+/**
+  String class wrapper with a preallocated buffer of size buff_sz
+
+  This class allows to replace sequences of:
+     char buff[12345];
+     String str(buff, sizeof(buff));
+     str.length(0);
+  with a simple equivalent declaration:
+     StringBuffer<12345> str;
+*/
+
+template<size_t buff_sz>
+class StringBuffer : public String
+{
+  char buff[buff_sz];
+
+public:
+  StringBuffer() : String(buff, buff_sz, &my_charset_bin) { length(0); }
+  explicit StringBuffer(const CHARSET_INFO *cs) : String(buff, buff_sz, cs)
+  {
+    length(0);
+  }
+  StringBuffer(const char *str, size_t length, const CHARSET_INFO *cs)
+    : String(buff, buff_sz, cs)
+  {
+    set(str, length, cs);
+  }
+};
+
+
 static inline bool check_if_only_end_space(CHARSET_INFO *cs,
                                            const char *str, 
                                            const char *end)

sql/sql_union.cc

@@ -620,6 +620,7 @@ bool st_select_lex_unit::exec()
   ulonglong add_rows=0;
   ha_rows examined_rows= 0;
   DBUG_ENTER("st_select_lex_unit::exec");
+  bool was_executed= executed;
 
   if (executed && !uncacheable && !describe)
     DBUG_RETURN(FALSE);
@@ -629,6 +630,9 @@ bool st_select_lex_unit::exec()
   
   saved_error= optimize();
 
+  if (!was_executed && thd->lex->query_plan_footprint)
+    save_union_qpf(thd->lex->query_plan_footprint);
+
   if (uncacheable || !item || !item->assigned() || describe)
   {
     for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())
@@ -776,6 +780,9 @@ bool st_select_lex_unit::exec()
         if (!fake_select_lex->ref_pointer_array)
           fake_select_lex->n_child_sum_items+= global_parameters->n_sum_items;
         
+        if (!was_executed && thd->lex->query_plan_footprint)
+          save_union_qpf_part2(thd->lex->query_plan_footprint);
+
         saved_error= mysql_select(thd, &fake_select_lex->ref_pointer_array,
                               &result_table_list,
                               0, item_list, NULL,

sql/sql_update.cc

@@ -260,7 +260,7 @@ int mysql_update(THD *thd,
   bool		can_compare_record;
   int           res;
   int		error, loc_error;
-  uint          used_index, dup_key_found;
+  uint          dup_key_found;
   bool          need_sort= TRUE;
   bool          reverse= FALSE;
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
@@ -270,12 +270,16 @@ int mysql_update(THD *thd,
   ha_rows	updated, found;
   key_map	old_covering_keys;
   TABLE		*table;
-  SQL_SELECT	*select;
+  SQL_SELECT	*select= NULL;
   READ_RECORD	info;
   SELECT_LEX    *select_lex= &thd->lex->select_lex;
   ulonglong     id;
   List<Item> all_fields;
   killed_state killed_status= NOT_KILLED;
+  Update_plan query_plan;
+  query_plan.index= MAX_KEY;
+  query_plan.using_filesort= FALSE;
+  bool apc_target_enabled= false; // means was enabled *by code this function*
   DBUG_ENTER("mysql_update");
 
   if (open_tables(thd, &table_list, &table_count, 0))
@@ -310,10 +314,16 @@ int mysql_update(THD *thd,
     my_error(ER_NON_UPDATABLE_TABLE, MYF(0), table_list->alias, "UPDATE");
     DBUG_RETURN(1);
   }
+  
+  //psergey-todo: Ugly, discuss with Sanja
+  query_plan.updating_a_view= test(table_list->view);
+  
   /* Calculate "table->covering_keys" based on the WHERE */
   table->covering_keys= table->s->keys_in_use;
   table->quick_keys.clear_all();
 
+  query_plan.select_lex= &thd->lex->select_lex;
+  query_plan.table= table;
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   /* Force privilege re-checking for views after they have been opened. */
   want_privilege= (table_list->view ? UPDATE_ACL :
@@ -370,7 +380,12 @@ int mysql_update(THD *thd,
     Item::cond_result cond_value;
     conds= remove_eq_conds(thd, conds, &cond_value);
     if (cond_value == Item::COND_FALSE)
+    {
       limit= 0;                                   // Impossible WHERE
+      query_plan.set_impossible_where();
+      if (thd->lex->describe)
+        goto exit_without_my_ok;
+    }
   }
 
   /*
@@ -400,6 +415,10 @@ int mysql_update(THD *thd,
   if (error || !limit || thd->is_error() ||
       (select && select->check_quick(thd, safe_update, limit)))
   {
+    query_plan.set_impossible_where();
+    if (thd->lex->describe)
+      goto exit_without_my_ok;
+
     delete select;
     free_underlaid_joins(thd, select_lex);
     /*
@@ -438,16 +457,16 @@ int mysql_update(THD *thd,
   if (select && select->quick && select->quick->unique_key_range())
   { // Single row select (always "ordered"): Ok to use with key field UPDATE
     need_sort= FALSE;
-    used_index= MAX_KEY;
+    query_plan.index= MAX_KEY;
     used_key_is_modified= FALSE;
   }
   else
   {
-    used_index= get_index_for_order(order, table, select, limit,
+    query_plan.index= get_index_for_order(order, table, select, limit,
                                           &need_sort, &reverse);
     if (select && select->quick)
     {
-      DBUG_ASSERT(need_sort || used_index == select->quick->index);
+      DBUG_ASSERT(need_sort || query_plan.index == select->quick->index);
       used_key_is_modified= (!select->quick->unique_key_range() &&
                              select->quick->is_keys_used(table->write_set));
     }
@@ -455,15 +474,39 @@ int mysql_update(THD *thd,
     {
       if (need_sort)
       { // Assign table scan index to check below for modified key fields:
-        used_index= table->file->key_used_on_scan;
+        query_plan.index= table->file->key_used_on_scan;
       }
-      if (used_index != MAX_KEY)
+      if (query_plan.index != MAX_KEY)
       { // Check if we are modifying a key that we are used to search with:
-        used_key_is_modified= is_key_used(table, used_index, table->write_set);
+        used_key_is_modified= is_key_used(table, query_plan.index, table->write_set);
       }
     }
   }
   
+  /* 
+    Query optimization is finished at this point.
+     - Save the decisions in the query plan
+     - if we're running EXPLAIN UPDATE, get out
+  */
+  query_plan.select= select;
+  query_plan.possible_keys= table->quick_keys;
+  query_plan.table_rows= table->file->stats.records;
+  
+  /*
+    Ok, we have generated a query plan for the UPDATE.
+     - if we're running EXPLAIN UPDATE, goto produce explain output 
+     - otherwise, execute the query plan
+  */
+  if (thd->lex->describe)
+    goto exit_without_my_ok;
+
+  query_plan.save_query_plan_footprint(thd->lex->query_plan_footprint);
+  thd->apc_target.enable();
+  apc_target_enabled= true;
+  DBUG_EXECUTE_IF("show_explain_probe_update_exec_start", 
+                  dbug_serve_apcs(thd, 1););
+
+
   if (used_key_is_modified || order ||
       partition_key_modified(table, table->write_set))
   {
@@ -476,8 +519,8 @@ int mysql_update(THD *thd,
     DBUG_ASSERT(table->read_set == &table->def_read_set);
     DBUG_ASSERT(table->write_set == &table->def_write_set);
 
-    if (used_index < MAX_KEY && old_covering_keys.is_set(used_index))
+    if (query_plan.index < MAX_KEY && old_covering_keys.is_set(query_plan.index))
-      table->add_read_columns_used_by_index(used_index);
+      table->add_read_columns_used_by_index(query_plan.index);
     else
       table->use_all_columns();
 
@@ -537,22 +580,22 @@ int mysql_update(THD *thd,
 
       /*
         When we get here, we have one of the following options:
-        A. used_index == MAX_KEY
+        A. query_plan.index == MAX_KEY
            This means we should use full table scan, and start it with
            init_read_record call
-        B. used_index != MAX_KEY
+        B. query_plan.index != MAX_KEY
            B.1 quick select is used, start the scan with init_read_record
            B.2 quick select is not used, this is full index scan (with LIMIT)
                Full index scan must be started with init_read_record_idx
       */
 
-      if (used_index == MAX_KEY || (select && select->quick))
+      if (query_plan.index == MAX_KEY || (select && select->quick))
       {
         if (init_read_record(&info, thd, table, select, 0, 1, FALSE))
           goto err;
       }
       else
-        init_read_record_idx(&info, thd, table, 1, used_index, reverse);
+        init_read_record_idx(&info, thd, table, 1, query_plan.index, reverse);
 
       thd_proc_info(thd, "Searching rows for update");
       ha_rows tmp_limit= limit;
@@ -618,6 +661,7 @@ int mysql_update(THD *thd,
 	select= new SQL_SELECT;
 	select->head=table;
       }
+      //psergey-todo: disable SHOW EXPLAIN because the plan was deleted? 
       if (reinit_io_cache(&tempfile,READ_CACHE,0L,0,0))
 	error=1; /* purecov: inspected */
       select->file=tempfile;			// Read row ptrs from this file
@@ -901,6 +945,8 @@ int mysql_update(THD *thd,
   if (!transactional_table && updated > 0)
     thd->transaction.stmt.modified_non_trans_table= TRUE;
 
+  thd->apc_target.disable(); //psergey-todo.
+  apc_target_enabled= false;
   end_read_record(&info);
   delete select;
   thd_proc_info(thd, "end");
@@ -974,11 +1020,36 @@ int mysql_update(THD *thd,
   DBUG_RETURN((error >= 0 || thd->is_error()) ? 1 : 0);
 
 err:
+  if (apc_target_enabled)
+    thd->apc_target.disable();
+
   delete select;
   free_underlaid_joins(thd, select_lex);
   table->disable_keyread();
   thd->abort_on_warning= 0;
   DBUG_RETURN(1);
+
+exit_without_my_ok:
+  DBUG_ASSERT(!apc_target_enabled);
+  query_plan.save_query_plan_footprint(thd->lex->query_plan_footprint);
+  
+  select_send *result;
+  //bool printed_anything;
+  if (!(result= new select_send()))
+    return 1;                               /* purecov: inspected */
+  List<Item> dummy; /* note: looked in 5.6 and they too use a dummy list like this */
+  result->prepare(dummy, &thd->lex->unit);
+  thd->send_explain_fields(result);
+  int err2= thd->lex->query_plan_footprint->print_explain(result, 0 /* explain flags*/);
+
+  if (err2)
+    result->abort_result_set();
+  else
+    result->send_eof();
+
+  delete select;
+  free_underlaid_joins(thd, select_lex);
+  DBUG_RETURN((error >= 0 || thd->is_error()) ? 1 : 0);
 }
 
 /*
@@ -1398,8 +1469,24 @@ bool mysql_multi_update(THD *thd,
                         multi_update **result)
 {
   bool res;
+  select_result *output;
+  bool explain= test(thd->lex->describe);
   DBUG_ENTER("mysql_multi_update");
   
+  if (explain)
+  {
+    /* Handle EXPLAIN UPDATE */
+    if (!(output= new select_send()) ||
+        thd->send_explain_fields(output))
+    {
+      delete output;
+      DBUG_RETURN(TRUE);
+    }
+    select_lex->set_explain_type(FALSE);
+    *result= NULL; /* no multi_update object */
+  }
+  else
+  {
     if (!(*result= new multi_update(table_list,
                                    &thd->lex->select_lex.leaf_tables,
                                    fields, values,
@@ -1407,11 +1494,12 @@ bool mysql_multi_update(THD *thd,
     {
       DBUG_RETURN(TRUE);
     }
+    output= *result;
+  }
 
   thd->abort_on_warning= test(thd->variables.sql_mode &
                               (MODE_STRICT_TRANS_TABLES |
                                MODE_STRICT_ALL_TABLES));
-
   List<Item> total_list;
 
   res= mysql_select(thd, &select_lex->ref_pointer_array,
@@ -1421,12 +1509,21 @@ bool mysql_multi_update(THD *thd,
                     (ORDER *)NULL,
                     options | SELECT_NO_JOIN_CACHE | SELECT_NO_UNLOCK |
                     OPTION_SETUP_TABLES_DONE,
-                    *result, unit, select_lex);
+                    output, unit, select_lex);
 
   DBUG_PRINT("info",("res: %d  report_error: %d", res, (int) thd->is_error()));
   res|= thd->is_error();
   if (unlikely(res))
     (*result)->abort_result_set();
+  else
+  {
+    if (explain)
+    {
+      thd->lex->query_plan_footprint->print_explain(output, 0);
+      output->send_eof(); 
+      delete output;
+    }
+  }
   thd->abort_on_warning= 0;
   DBUG_RETURN(res);
 }

sql/sql_yacc.yy

@@ -12029,13 +12029,21 @@ describe:
           }
         | describe_command opt_extended_describe
           { Lex->describe|= DESCRIBE_NORMAL; }
-          select
+          explanable_command
           {
             LEX *lex=Lex;
             lex->select_lex.options|= SELECT_DESCRIBE;
           }
         ;
 
+explanable_command:
+          select
+        | insert
+        | replace
+        | update
+        | delete
+        ;
+
 describe_command:
           DESC
         | DESCRIBE

support-files/build-tags

@@ -6,7 +6,7 @@ filter='\.cc$\|\.c$\|\.h$\|\.yy$'
 list="find . -type f"
 bzr root >/dev/null 2>/dev/null && list="bzr ls --from-root -R --kind=file --versioned"
 
-$list |grep $filter |while read f; 
+$list |grep $filter | grep -v gen-cpp |while read f; 
 do
 	 etags -o TAGS --append $f
 done