MDEV-8796 Delete with sub query with information_schema.TABLES deletes too many rows

make_cond_for_info_schema() does preserve outer fields

Author: vuvova

mysql-test/r/information_schema2.result

@@ -6,15 +6,15 @@ select variable_name from information_schema.session_variables where variable_na
 (select variable_name from information_schema.session_variables where variable_name = 'basedir');
 variable_name
 BASEDIR
-create table t1 (a char);
-insert t1 values ('a'),('t'),('z');
-flush status;
-select a, exists (select 1 from information_schema.columns where table_schema=concat('tes',a)) from t1;
-a	exists (select 1 from information_schema.columns where table_schema=concat('tes',a))
-a	0
-t	1
-z	0
-show status like 'created_tmp_tables';
-Variable_name	Value
-Created_tmp_tables	38
-drop table t1;
+create table t1 (x int);
+create table t2 (x int);
+create table t3 (x int);
+create table t4 AS select table_name from information_schema.TABLES where table_schema = database() and table_type = 'BASE TABLE' ;
+delete from t4 where table_name not in (select table_name from information_schema.TABLES where table_schema = database() and table_type = 'BASE TABLE');
+select * from t4;
+table_name
+t1
+t2
+t3
+t4
+drop table t1, t2, t3, t4;

mysql-test/t/information_schema2.test

@@ -8,15 +8,12 @@ select variable_name from information_schema.session_variables where variable_na
 (select variable_name from information_schema.session_variables where variable_name = 'basedir');
 
 #
-# information_schema tables inside subqueries, they should not be re-populated
-# (i_s.columns needs to scan i_s itself, creating a tmp table for every i_s
-# table. if it's re-populated, it'll do that multiple times)
+# MDEV-8796 Delete with sub query with information_schema.TABLES deletes too many rows
 #
-create table t1 (a char);
-insert t1 values ('a'),('t'),('z');
-flush status;
-select a, exists (select 1 from information_schema.columns where table_schema=concat('tes',a)) from t1;
-# fix the result in ps-protocol
---replace_result 39 38
-show status like 'created_tmp_tables';
-drop table t1;
+create table t1 (x int);
+create table t2 (x int);
+create table t3 (x int);
+create table t4 AS select table_name from information_schema.TABLES where table_schema = database() and table_type = 'BASE TABLE' ;
+delete from t4 where table_name not in (select table_name from information_schema.TABLES where table_schema = database() and table_type = 'BASE TABLE');
+select * from t4;
+drop table t1, t2, t3, t4;

sql/sql_show.cc

@@ -7730,13 +7730,14 @@ bool get_schema_tables_result(JOIN *join,
  TABLE_LIST *table_list= tab->table->pos_in_table_list;
  if (table_list->schema_table && thd->fill_information_schema_tables())
  {
-#if MYSQL_VERSION_ID > 100105
-#error I_S tables only need to be re-populated if make_cond_for_info_schema() will preserve outer fields
- bool is_subselect= (&lex->unit != lex->current_select->master_unit() &&
- lex->current_select->master_unit()->item);
-#else
-#define is_subselect false
-#endif
+ /*
+ I_S tables only need to be re-populated if make_cond_for_info_schema()
+ preserves outer fields
+ */
+ bool is_subselect= &lex->unit != lex->current_select->master_unit() &&
+ lex->current_select->master_unit()->item &&
+ tab->select_cond &&
+ tab->select_cond->used_tables() & OUTER_REF_TABLE_BIT;
 
  /* A value of 0 indicates a dummy implementation */
  if (table_list->schema_table->fill_table == 0)