BUG#938131: Subquery materialization is not used in CREATE TABLE SELECT

- Enable subquery materialization for CREATE TABLE ... SELECT.

mysql-test/r/subselect_sj_mat.result

@@ -1898,6 +1898,25 @@ WHERE 'condition'='impossible'
 MIN(a)
 NULL
 DROP TABLE t1;
+#
+# BUG#938131: Subquery materialization is not used in CREATE TABLE SELECT
+# 
+CREATE TABLE t1(a int);
+INSERT INTO t1 values(1),(2);
+CREATE TABLE t2(a int);
+INSERT INTO t2 values(1),(2);
+# Should use Materialization:
+EXPLAIN SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	
+2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	2	Using temporary
+flush status;
+CREATE TABLE t3 SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
+SHOW STATUS LIKE 'Created_tmp_tables';
+Variable_name	Value
+Created_tmp_tables	2
+DROP TABLE t1,t2,t3;
 # This must be at the end:
 set optimizer_switch=@subselect_sj_mat_tmp;
 set join_cache_level=@save_join_cache_level;

mysql-test/t/subselect_sj_mat.test

@@ -1559,6 +1559,20 @@ WHERE a IN (
 
 DROP TABLE t1;
 
+--echo #
+--echo # BUG#938131: Subquery materialization is not used in CREATE TABLE SELECT
+--echo # 
+CREATE TABLE t1(a int);
+INSERT INTO t1 values(1),(2);
+CREATE TABLE t2(a int);
+INSERT INTO t2 values(1),(2);
+--echo # Should use Materialization:
+EXPLAIN SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
+flush status;
+CREATE TABLE t3 SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
+SHOW STATUS LIKE 'Created_tmp_tables';
+DROP TABLE t1,t2,t3;
+
 --echo # This must be at the end:
 set optimizer_switch=@subselect_sj_mat_tmp;
 set join_cache_level=@save_join_cache_level;

sql/opt_subselect.cc

@@ -251,8 +251,8 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs,
          Subquery !contains {GROUP BY, ORDER BY [LIMIT],
          aggregate functions}) && subquery predicate is not under "NOT IN"))
 
-    (*) The subquery must be part of a SELECT statement. The current
-         condition also excludes multi-table update statements.
+    (*) The subquery must be part of a SELECT or CREATE TABLE ... SELECT statement.
+        The current condition also excludes multi-table update statements.
   A note about prepared statements: we want the if-branch to be taken on
   PREPARE and each EXECUTE. The rewrites are only done once, but we need 
   select_lex->sj_subselects list to be populated for every EXECUTE. 
@@ -261,7 +261,8 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs,
   if (optimizer_flag(thd, OPTIMIZER_SWITCH_MATERIALIZATION) &&      // 0
         !child_select->is_part_of_union() &&                          // 1
         parent_unit->first_select()->leaf_tables.elements &&          // 2
-        thd->lex->sql_command == SQLCOM_SELECT &&                     // *
+        (thd->lex->sql_command == SQLCOM_SELECT ||                     // *
+         thd->lex->sql_command == SQLCOM_CREATE_TABLE) &&              // *
         child_select->outer_select()->leaf_tables.elements &&           // 2A
         subquery_types_allow_materialization(in_subs) &&
         (in_subs->is_top_level_item() ||                               //3