BUG#992942 & MDEV-325: Pre-liminary commit for testing

mysql-test/r/show_explain.result

@@ -825,9 +825,67 @@ pk	data
 19	data1
 20	data1
 drop table t1;
-drop table t0;
 # 
 # Check that the I_S table is invisible
 # 
 select table_name from information_schema.tables where table_schema='information_schema' and table_name like '%explain%';
 table_name
+# 
+# MDEV-325: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN is different from standard EXPLAIN: type ALL vs 'index_merge'..
+#
+CREATE TABLE t1 (a INT, b INT, KEY(a), KEY(b)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES
+(8,0),(128,5050),(5372,8),(234,7596),(2,0),(2907,8930),(1,0),
+(0,5224),(8,7638),(960,5),(9872,1534),(0,2295),(3408,9809),
+(7,0),(1168,0),(2089,5570),(0,205),(88,1018),(0,26528),
+(0,0),(4,5567),(1444,145),(6,0),(1,7535),(7793,534),(70,9),
+(178,1),(44,5),(189,0),(3,0);
+EXPLAIN
+SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	5,5	NULL	8	Using sort_union(a,b); Using where; Using filesort
+set @show_explain_probe_select_id=1;
+set debug_dbug='d,show_explain_probe_join_exec_start';
+SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	5,5	NULL	8	Using sort_union(a,b); Using where; Using filesort
+Warnings:
+Note	1003	SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b
+a+SLEEP(0.01)
+0
+5372
+70
+0
+0
+0
+0
+set @show_explain_probe_select_id=1;
+set debug_dbug='d,show_explain_probe_do_select';
+SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	5,5	NULL	8	Using sort_union(a,b); Using where; Using filesort
+Warnings:
+Note	1003	SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b
+a+SLEEP(0.01)
+0
+5372
+70
+0
+0
+0
+0
+set debug_dbug='';
+drop table t1;
+drop table t0;

mysql-test/t/show_explain.test

@@ -837,6 +837,7 @@ select * from t1 where pk between 10 and 20 for update;
 
 # run SHOW EXPLAIN on a frozen thread
 connection default;
+let $save_wait_condition= $wait_condition;
 let $wait_condition= select State='Sending data' from information_schema.processlist where id=$thr2;
 let $thr_default=`select connection_id()`;
 --source include/wait_condition.inc
@@ -864,14 +865,59 @@ reap;
 drop table t1;
 disconnect con3;
 disconnect con2;
-
+let $wait_condition= $save_wait_condition;
-## TODO: Test this: have several SHOW EXPLAIN requests be queued up for a
-##       thread and served together.
-
-drop table t0;
 
 --echo # 
 --echo # Check that the I_S table is invisible
 --echo # 
 select table_name from information_schema.tables where table_schema='information_schema' and table_name like '%explain%';
 
+--echo # 
+--echo # MDEV-325: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN is different from standard EXPLAIN: type ALL vs 'index_merge'..
+--echo #
+CREATE TABLE t1 (a INT, b INT, KEY(a), KEY(b)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES
+(8,0),(128,5050),(5372,8),(234,7596),(2,0),(2907,8930),(1,0),
+(0,5224),(8,7638),(960,5),(9872,1534),(0,2295),(3408,9809),
+(7,0),(1168,0),(2089,5570),(0,205),(88,1018),(0,26528),
+(0,0),(4,5567),(1444,145),(6,0),(1,7535),(7793,534),(70,9),
+(178,1),(44,5),(189,0),(3,0);
+
+EXPLAIN
+SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b;
+
+set @show_explain_probe_select_id=1;
+set debug_dbug='d,show_explain_probe_join_exec_start';
+--send
+SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b;
+
+connection default;
+--source include/wait_condition.inc
+evalp show explain for $thr2;
+
+connection con1;
+reap;
+
+set @show_explain_probe_select_id=1;
+set debug_dbug='d,show_explain_probe_do_select';
+--send
+SELECT a+SLEEP(0.01) FROM t1
+WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129
+ORDER BY b;
+
+connection default;
+--source include/wait_condition.inc
+evalp show explain for $thr2;
+
+connection con1;
+reap;
+
+set debug_dbug='';
+
+drop table t1;
+drop table t0;
+

sql/sql_select.cc

@@ -10686,6 +10686,9 @@ void JOIN::cleanup(bool full)
   */
   if (full)
   {
+    if (pre_sort_join_tab)
+      clean_pre_sort_join_tab();
+
     if (tmp_join)
       tmp_table_param.copy_field= 0;
     group_fields.delete_elements();
@@ -18908,6 +18911,8 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   TABLE *table;
   SQL_SELECT *select;
   JOIN_TAB *tab;
+  int err= 0;
+  bool quick_created= FALSE;
   DBUG_ENTER("create_sort_index");
 
   if (join->table_count == join->const_tables)
@@ -18915,6 +18920,43 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   tab=    join->join_tab + join->const_tables;
   table=  tab->table;
   select= tab->select;
+  
+  JOIN_TAB *save_pre_sort_join_tab= NULL;
+  if (join->pre_sort_join_tab)
+  {
+    /*
+      we've already been in this function, and stashed away the original access 
+      method in join->pre_sort_join_tab, restore it now.
+    */
+    
+    /* First, restore state of the handler */
+    if (join->pre_sort_index != MAX_KEY)
+    {
+      if (table->file->ha_index_or_rnd_end())
+        goto err;
+      if (join->pre_sort_idx_pushed_cond)
+      {
+        table->file->idx_cond_push(join->pre_sort_index,
+                                 join->pre_sort_idx_pushed_cond);
+      }
+    }
+    else
+    {
+      if (table->file->ha_index_or_rnd_end() || 
+          table->file->ha_rnd_init(TRUE))
+        goto err;
+    }
+
+    /* Second, restore access method parameters */
+    tab->records=           join->pre_sort_join_tab->records;
+    tab->select=            join->pre_sort_join_tab->select;
+    tab->select_cond=       join->pre_sort_join_tab->select_cond;
+    tab->type=              join->pre_sort_join_tab->type;
+    tab->read_first_record= join->pre_sort_join_tab->read_first_record; 
+
+    save_pre_sort_join_tab= join->pre_sort_join_tab;
+    join->pre_sort_join_tab= NULL;
+  }
 
   /* Currently ORDER BY ... LIMIT is not supported in subqueries. */
   DBUG_ASSERT(join->group_list || !join->is_in_subquery());
@@ -18970,6 +19012,7 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
 			    get_quick_select_for_ref(thd, table, &tab->ref, 
                                                      tab->found_records))))
 	goto err;
+      quick_created= TRUE;
     }
   }
 
@@ -18985,7 +19028,37 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   table->sort.found_records=filesort(thd, table,join->sortorder, length,
                                      select, filesort_limit, 0,
                                      &examined_rows);
+
+  if (quick_created)
+  {
+    /* This will delete the quick select. */
+    select->cleanup();
+  }
+
+  if (!join->pre_sort_join_tab)
+  {
+    if (save_pre_sort_join_tab)
+      join->pre_sort_join_tab= save_pre_sort_join_tab;
+    else if (!(join->pre_sort_join_tab= (JOIN_TAB*)thd->alloc(sizeof(JOIN_TAB))))
+      goto err;
+  }
+
+  *(join->pre_sort_join_tab)= *tab;
+  
+  if (table->file->inited == handler::INDEX)
+  {
+    // Save index #, save index condition
+    join->pre_sort_index= table->file->active_index;
+    join->pre_sort_idx_pushed_cond= table->file->pushed_idx_cond;
+    // no need to save key_read? 
+    err= table->file->ha_index_end();
+  }
+  else
+    join->pre_sort_index= MAX_KEY;
+
+  /*TODO: here, close the index scan, cancel index-only read. */
   tab->records= table->sort.found_records;	// For SQL_CALC_ROWS
+#if 0 
   if (select)
   {
     /*
@@ -19002,23 +19075,65 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
     tablesort_result_cache= table->sort.io_cache;
     table->sort.io_cache= NULL;
 
-    select->cleanup();				// filesort did select
+   // select->cleanup();				// filesort did select
     table->quick_keys.clear_all();  // as far as we cleanup select->quick
     table->intersect_keys.clear_all();
     table->sort.io_cache= tablesort_result_cache;
   }
+#endif
+  tab->select=NULL;
   tab->set_select_cond(NULL, __LINE__);
-  tab->last_inner= 0;
+//  tab->last_inner= 0;
-  tab->first_unmatched= 0;
+//  tab->first_unmatched= 0;
   tab->type=JT_ALL;				// Read with normal read_record
   tab->read_first_record= join_init_read_record;
+  tab->table->file->ha_index_or_rnd_end();
+  
+  if (err)
+    goto err;
+
   tab->join->examined_rows+=examined_rows;
-  table->disable_keyread(); // Restore if we used indexes
   DBUG_RETURN(table->sort.found_records == HA_POS_ERROR);
 err:
   DBUG_RETURN(-1);
 }
 
+void JOIN::clean_pre_sort_join_tab()
+{
+  TABLE *table=  pre_sort_join_tab->table;
+  /*
+   Note: we can come here for fake_select_lex object. That object will have
+   the table already deleted by st_select_lex_unit::cleanup().  
+    We rely on that fake_select_lex didn't have quick select.
+  */
+#if 0  
+  if (pre_sort_join_tab->select && pre_sort_join_tab->select->quick)
+  {
+    /*
+      We need to preserve tablesort's output resultset here, because
+      QUICK_INDEX_MERGE_SELECT::~QUICK_INDEX_MERGE_SELECT (called by
+      SQL_SELECT::cleanup()) may free it assuming it's the result of the quick
+      select operation that we no longer need. Note that all the other parts of
+      this data structure are cleaned up when
+      QUICK_INDEX_MERGE_SELECT::get_next encounters end of data, so the next
+      SQL_SELECT::cleanup() call changes sort.io_cache alone.
+    */
+    IO_CACHE *tablesort_result_cache;
+
+    tablesort_result_cache= table->sort.io_cache;
+    table->sort.io_cache= NULL;
+    pre_sort_join_tab->select->cleanup();
+    table->quick_keys.clear_all();  // as far as we cleanup select->quick
+    table->intersect_keys.clear_all();
+    table->sort.io_cache= tablesort_result_cache;
+  }
+#endif
+  //table->disable_keyread(); // Restore if we used indexes
+  if (pre_sort_join_tab->select && pre_sort_join_tab->select->quick)
+  {
+    pre_sort_join_tab->select->cleanup();
+  }
+}
 /*****************************************************************************
   Remove duplicates from tmp table
   This should be recoded to add a unique index to the table and remove
@@ -21502,6 +21617,7 @@ int JOIN::print_explain(select_result_sink *result, uint8 explain_flags,
       tmp4.length(0);
       quick_type= -1;
       QUICK_SELECT_I *quick= NULL;
+      JOIN_TAB *saved_join_tab= NULL;
 
       /* Don't show eliminated tables */
       if (table->map & join->eliminated_tables)
@@ -21510,6 +21626,12 @@ int JOIN::print_explain(select_result_sink *result, uint8 explain_flags,
         continue;
       }
 
+      if (tab == first_top_tab && pre_sort_join_tab)
+      {
+        saved_join_tab= tab;
+        tab= pre_sort_join_tab;
+      }
+
       item_list.empty();
       /* id */
       item_list.push_back(new Item_uint((uint32)select_id));
@@ -21656,7 +21778,6 @@ int JOIN::print_explain(select_result_sink *result, uint8 explain_flags,
                  keylen_str_buf);
         tmp3.append(keylen_str_buf, length, cs);
 /*<<<<<<< TREE
-      }
       if ((is_hj || tab->type==JT_RANGE || tab->type == JT_INDEX_MERGE) &&
           tab->select && tab->select->quick)
 =======*/
@@ -21977,6 +22098,9 @@ int JOIN::print_explain(select_result_sink *result, uint8 explain_flags,
 	item_list.push_back(new Item_string(str, len, cs));
       }
       
+      if (saved_join_tab)
+        tab= saved_join_tab;
+
       // For next iteration
       used_tables|=table->map;
       if (result->send_data(item_list))

sql/sql_select.h

@@ -903,6 +903,14 @@ protected:
 
 public:
   JOIN_TAB *join_tab, **best_ref;
+  
+  /* 
+    Saved join_tab for pre_sorting. create_sort_index() will save here.. 
+  */
+  JOIN_TAB *pre_sort_join_tab;
+  uint pre_sort_index;
+  Item *pre_sort_idx_pushed_cond;
+  void clean_pre_sort_join_tab();
 
   /*
     For "Using temporary+Using filesort" queries, JOIN::join_tab can point to
@@ -1293,6 +1301,8 @@ public:
     outer_ref_cond= pseudo_bits_cond= NULL;
     in_to_exists_where= NULL;
     in_to_exists_having= NULL;
+
+    pre_sort_join_tab= NULL;
   }
 
   int prepare(Item ***rref_pointer_array, TABLE_LIST *tables, uint wind_num,

sql/sql_show.cc

@@ -8495,7 +8495,7 @@ ST_FIELD_INFO show_explain_fields_info[]=
     SKIP_OPEN_TABLE},
   {"table", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0 /*value*/, MY_I_S_MAYBE_NULL,
    "table", SKIP_OPEN_TABLE},
-  {"type", 10, MYSQL_TYPE_STRING, 0, MY_I_S_MAYBE_NULL, "type", SKIP_OPEN_TABLE},
+  {"type", 11, MYSQL_TYPE_STRING, 0, MY_I_S_MAYBE_NULL, "type", SKIP_OPEN_TABLE},
   {"possible_keys", NAME_CHAR_LEN*MAX_KEY, MYSQL_TYPE_STRING, 0/*value*/,
     MY_I_S_MAYBE_NULL, "possible_keys", SKIP_OPEN_TABLE},
   {"key", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0/*value*/, MY_I_S_MAYBE_NULL,