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MDEV-5106: Server crashes in Explain_union::print_explain on ER_TOO_BIG_SELECT

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- Don't save UNION's EXPLAIN data if optimization failed with 
  an error. We could end up saving incomplete plan, which will 
  cause a crash when we attempt to print it.
This commit is contained in:
Sergey Petrunya 2013-10-10 20:30:32 +04:00
parent 582ecb2a25
commit 094f70fd19
5 changed files with 30 additions and 2 deletions
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13
mysql-test/r/explain_slowquerylog.result
View File

@ -26,3 +26,16 @@ SELECT 1;
EXPLAIN PARTITIONS SELECT 1 ;
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL No tables used
#
# MDEV-5106: Server crashes in Explain_union::print_explain on ER_TOO_BIG_SELECT with explain in slow log
#
CREATE TABLE t1 (i INT) ENGINE=MyISAM;
INSERT INTO t1 VALUES
(1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
SET max_join_size = 10;
( SELECT ta.* FROM t1 ta, t1 tb ) UNION ( SELECT * FROM t1 );
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET MAX_JOIN_SIZE=# if the SELECT is okay
SELECT 'Server still alive?' as 'Yes';
Yes
Server still alive?
DROP TABLE t1;

1
mysql-test/t/explain_non_select.test
View File

@ -169,4 +169,3 @@ explain insert into t2 values
(11, 1+(select max(a+1) from t1));
drop table t1,t2;

12
mysql-test/t/explain_slowquerylog.test
View File

@ -35,3 +35,15 @@ SELECT 1;
EXPLAIN PARTITIONS SELECT 1 ;
--echo #
--echo # MDEV-5106: Server crashes in Explain_union::print_explain on ER_TOO_BIG_SELECT with explain in slow log
--echo #
CREATE TABLE t1 (i INT) ENGINE=MyISAM;
INSERT INTO t1 VALUES
(1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
SET max_join_size = 10;
--error ER_TOO_BIG_SELECT
( SELECT ta.* FROM t1 ta, t1 tb ) UNION ( SELECT * FROM t1 );
SELECT 'Server still alive?' as 'Yes';
DROP TABLE t1;

4
sql/sql_explain.cc
View File

@ -157,6 +157,10 @@ bool print_explain_query(LEX *lex, THD *thd, String *str)
}
/*
Return tabular EXPLAIN output as a text string
*/
bool Explain_query::print_explain_str(THD *thd, String *out_str)
{
List<Item> fields;

2
sql/sql_union.cc
View File

@ -630,7 +630,7 @@ bool st_select_lex_unit::exec()
saved_error= optimize();
if (!was_executed && thd->lex->explain)
if (!saved_error && !was_executed && thd->lex->explain)
save_union_explain(thd->lex->explain);
if (uncacheable || !item || !item->assigned() || describe)