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Filing based on Elena Stepanova's example in CSC#8345:
drop table if exists t1, t2; create table t1 (a int); insert into t1 values (1); create table t2 (b int, c int);
MariaDB [test]> replace into t2 select 100, (select a from t1); Query OK, 1 row affected (0.05 sec) Records: 1 Duplicates: 0 Warnings: 0 MariaDB [test]> explain replace into t2 select 100, (select a from t1); ERROR 1136 (21S01): Column count doesn't match value count at row 1
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MDEV-7220 Materialization strategy is not used for REPLACE ... SELECT
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select_insert::prepare is called twice.
The first call is from here:
#0 select_insert::prepare (this=0x7fffa0008288, values=..., u=0x31d4d60) at /home/psergey/dev2/10.0/sql/sql_insert.cc:3364 #1 0x0000000000699753 in JOIN::prepare (this=0x7fffa0075068, rref_pointer_array=0x31d56c0, tables_init=0x0, wild_num=0, conds_init=0x0, og_num=0, order_init=0x0, skip_order_by=false, group_init=0x0, having_init=0x0, proc_param_init=0x0, select_lex_arg=0x31d5448, unit_arg=0x31d4d60) at /home/psergey/dev2/10.0/sql/sql_select.cc:967 #2 0x00000000006a17bb in mysql_select (thd=0x31d1050, rref_pointer_array=0x31d56c0, tables=0x0, wild_num=0, fields=..., conds=0x0, og_num=0, order=0x0, group=0x0, having=0x0, proc_param=0x0, select_options=3489925892, result=0x7fffa0008288, unit=0x31d4d60, select_lex=0x31d5448) at /home/psergey/dev2/10.0/sql/sql_select.cc:3286 #3 0x0000000000697b7b in handle_select (thd=0x31d1050, lex=0x31d4c98, result=0x7fffa0008288, setup_tables_done_option=1073741824) at /home/psergey/dev2/10.0/sql/sql_select.cc:373
and it succeeds.
For the second call, see the previous comment. The second call should not have
been made.
BTW, EXPLAIN-in-the-slow-query-log feature is not affected by this:
... # Query_time: 0.000276 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0 SET timestamp=1417011689; set log_slow_verbosity='explain,query_plan'; # Time: 141126 17:21:33 # User@Host: root[root] @ localhost [] # Thread_id: 2 Schema: j10 QC_hit: No # Query_time: 0.069501 Lock_time: 0.001863 Rows_sent: 0 Rows_examined: 0 # Full_scan: Yes Full_join: No Tmp_table: No Tmp_table_on_disk: No # Filesort: No Filesort_on_disk: No Merge_passes: 0 Priority_queue: No # # explain: id select_type table type possible_keys key key_len ref rows Extra # explain: 1 PRIMARY NULL NULL NULL NULL NULL NULL NULL No tables used # explain: 2 SUBQUERY t1 ALL NULL NULL NULL NULL 1 # SET timestamp=1417011693; replace into t2 select 100, (select a from t1);
The error is generated here:
select_describe(join, join->select_lex->select_number=1) calls
mysql_explain_union for the subquery.
mysql_explain_union calls mysql_select, which makes this call
//here is EXPLAIN of subselect or derived table if (join->change_result(result)) { DBUG_RETURN(TRUE); }where the result is select_insert object. The number of columns select_insert
expects is not (and doesn't have to be) equal to number of columns produced by
the subquery, and we get an error.