From f3b10354a97a0815d36abbfd25a5f10489a3eaab Mon Sep 17 00:00:00 2001
From: Sergei Golubchik <serg@mariadb.org>
Date: Tue, 24 Nov 2020 21:33:50 +0100
Subject: [PATCH] MDEV-24230 subquery on information_schema fails with error
 message

disable thd->count_cuted_fields when populating internal temporary
tables for I_S, because this is how SELECT works standalone.
And if the SELECT is a part of INSERT or UPDATE or RETURN or SET or
anything else that enables thd->count_cuted_fields, this counting should
only apply when storing the result of the SELECT in a field or a
variable, not when populating internal temporary tables for I_S.
---
 mysql-test/main/information_schema.result |  9 +++++++--
 mysql-test/main/information_schema.test   | 10 ++++++++--
 sql/sql_show.cc                           | 10 +---------
 3 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/mysql-test/main/information_schema.result b/mysql-test/main/information_schema.result
index f7bff84e220..52bb7601c22 100644
--- a/mysql-test/main/information_schema.result
+++ b/mysql-test/main/information_schema.result
@@ -2202,8 +2202,6 @@ SCHEMA_NAME
 # End of 10.1 tests
 #
 #
-# Start of 10.2 Test
-#
 # MDEV-14836: Assertion `m_status == DA_ERROR' failed in
 # Diagnostics_area::sql_errno upon query from I_S with LIMIT ROWS EXAMINED
 #
@@ -2276,5 +2274,12 @@ TABLE_SCHEMA	TABLE_NAME	CONSTRAINT_NAME	CHECK_CLAUSE	CONSTRAINT_CATALOG	CONSTRAI
 test	t	a	`i` > 0	def	test
 drop table t;
 #
+# MDEV-24230 subquery on information_schema fails with error message
+#
+create table t1 (n int);
+create table t2 (n int);
+insert into t1 set n = (select table_rows from information_schema.tables where table_name='t2');
+drop table t1, t2;
+#
 # End of 10.3 tests
 #
diff --git a/mysql-test/main/information_schema.test b/mysql-test/main/information_schema.test
index d090921c97c..ba6e64a1c70 100644
--- a/mysql-test/main/information_schema.test
+++ b/mysql-test/main/information_schema.test
@@ -1925,8 +1925,6 @@ SELECT SCHEMA_NAME from information_schema.schemata where schema_name=REPEAT('a'
 --echo # End of 10.1 tests
 --echo #
 
---echo #
---echo # Start of 10.2 Test
 --echo #
 --echo # MDEV-14836: Assertion `m_status == DA_ERROR' failed in
 --echo # Diagnostics_area::sql_errno upon query from I_S with LIMIT ROWS EXAMINED
@@ -2000,6 +1998,14 @@ from information_schema.TABLE_CONSTRAINTS tc
 
 drop table t;
 
+--echo #
+--echo # MDEV-24230 subquery on information_schema fails with error message
+--echo #
+create table t1 (n int);
+create table t2 (n int);
+insert into t1 set n = (select table_rows from information_schema.tables where table_name='t2');
+drop table t1, t2;
+
 --echo #
 --echo # End of 10.3 tests
 --echo #
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index 8f21d2009a6..909963f5f7a 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -3695,7 +3695,6 @@ static bool show_status_array(THD *thd, const char *wild,
   char name_buffer[NAME_CHAR_LEN];
   int len;
   SHOW_VAR tmp, *var;
-  Check_level_instant_set check_level_save(thd, CHECK_FIELD_IGNORE);
   bool res= FALSE;
   CHARSET_INFO *charset= system_charset_info;
   DBUG_ENTER("show_status_array");
@@ -8669,13 +8668,6 @@ static int optimize_schema_tables_memory_usage(TABLE_LIST *table_list)
     DBUG_ASSERT(table->s->keys == 0);
     DBUG_ASSERT(table->s->uniques == 0);
 
-    // XXX HACK HACK HACK: in a stored function, RETURN (SELECT ...)
-    // enables warnings (in THD::sp_eval_expr) for the whole val_xxx/store pair,
-    // while the intention is to warn only for store(). Until this is
-    // fixed let's avoid data truncation warnings in I_S->fill_table()
-    if (thd->count_cuted_fields == CHECK_FIELD_IGNORE)
-    {
-
     uchar *cur= table->field[0]->ptr;
     /* first recinfo could be a NULL bitmap, not an actual Field */
     from_recinfo= to_recinfo= p->start_recinfo + (cur != table->record[0]);
@@ -8709,7 +8701,6 @@ static int optimize_schema_tables_memory_usage(TABLE_LIST *table_list)
       to_recinfo++;
     }
     p->recinfo= to_recinfo;
-    } // XXX end of HACK HACK HACK
 
     // TODO switch from Aria to Memory if all blobs were optimized away?
     if (instantiate_tmp_table(table, p->keyinfo, p->start_recinfo, &p->recinfo,
@@ -8872,6 +8863,7 @@ bool get_schema_tables_result(JOIN *join,
       }
 
       Switch_to_definer_security_ctx backup_ctx(thd, table_list);
+      Check_level_instant_set check_level_save(thd, CHECK_FIELD_IGNORE);
       if (table_list->schema_table->fill_table(thd, table_list, cond))
       {
         result= 1;