Fix for BUG#21774: Column count doesn't match value count at row x

The cause of the bug was an incomplete fix for bug 18080.
The problem was that setup_tables() unconditionally reset the
name resolution context to its 'tables' argument, which pointed
to the first table of an SQL statement.

The bug fix limits resetting of the name resolution context in
setup_tables() only in the cases when the context was not set
by earlier parser/optimizer phases.

mysql-test/r/insert_select.result

@@ -695,6 +695,16 @@ CREATE TABLE t2 (z int, y int);
 CREATE TABLE t3 (a int, b int);
 INSERT INTO t3 (SELECT x, y FROM t1 JOIN t2 USING (y) WHERE z = 1);
 DROP TABLE IF EXISTS t1,t2,t3;
+CREATE DATABASE bug21774_1;
+CREATE DATABASE bug21774_2;
+CREATE TABLE bug21774_1.t1(id VARCHAR(10) NOT NULL,label VARCHAR(255));
+CREATE TABLE bug21774_2.t1(id VARCHAR(10) NOT NULL,label VARCHAR(255));
+CREATE TABLE bug21774_1.t2(id VARCHAR(10) NOT NULL,label VARCHAR(255));
+INSERT INTO bug21774_2.t1 SELECT t1.* FROM bug21774_1.t1;
+use bug21774_1;
+INSERT INTO bug21774_2.t1 SELECT t1.* FROM t1;
+DROP DATABASE bug21774_1;
+DROP DATABASE bug21774_2;
 CREATE DATABASE meow;
 CREATE TABLE table_target   ( mexs_id CHAR(8), messzeit TIMESTAMP, PRIMARY KEY (mexs_id));
 CREATE TABLE table_target2  ( mexs_id CHAR(8), messzeit TIMESTAMP, PRIMARY KEY (mexs_id));

mysql-test/t/insert_select.test

@@ -248,6 +248,24 @@ CREATE TABLE t3 (a int, b int);
 INSERT INTO t3 (SELECT x, y FROM t1 JOIN t2 USING (y) WHERE z = 1);
 DROP TABLE IF EXISTS t1,t2,t3;
 
+#
+# Bug #21774: Column count doesn't match value count at row x
+#
+CREATE DATABASE bug21774_1;
+CREATE DATABASE bug21774_2;
+
+CREATE TABLE bug21774_1.t1(id VARCHAR(10) NOT NULL,label VARCHAR(255));
+CREATE TABLE bug21774_2.t1(id VARCHAR(10) NOT NULL,label VARCHAR(255));
+CREATE TABLE bug21774_1.t2(id VARCHAR(10) NOT NULL,label VARCHAR(255));
+
+INSERT INTO bug21774_2.t1 SELECT t1.* FROM bug21774_1.t1;
+
+use bug21774_1;
+INSERT INTO bug21774_2.t1 SELECT t1.* FROM t1;
+
+DROP DATABASE bug21774_1;
+DROP DATABASE bug21774_2;
+
 #
 # Bug #20989: View '(null).(null)' references invalid table(s)... on
 #             SQL SECURITY INVOKER

sql/sql_base.cc

@@ -4453,7 +4453,20 @@ bool setup_tables(THD *thd, Name_resolution_context *context,
   uint tablenr= 0;
   DBUG_ENTER("setup_tables");
 
-  context->table_list= context->first_name_resolution_table= tables;
+  /*
+    Due to the various call paths that lead to setup_tables() it may happen
+    that context->table_list and context->first_name_resolution_table can be
+    NULL (this is typically done when creating TABLE_LISTs internally).
+    TODO:
+    Investigate all cases when this my happen, initialize the name resolution
+    context correctly in all those places, and remove the context reset below.
+  */
+  if (!context->table_list || !context->first_name_resolution_table)
+  {
+    /* Test whether the context is in a consistent state. */
+    DBUG_ASSERT(!context->first_name_resolution_table && !context->table_list);
+    context->table_list= context->first_name_resolution_table= tables;
+  }
 
   /*
     this is used for INSERT ... SELECT.

sql/sql_insert.cc

@@ -411,6 +411,15 @@ bool mysql_insert(THD *thd,TABLE_LIST *table_list,
   table= table_list->table;
 
   context= &thd->lex->select_lex.context;
+  /*
+    These three asserts test the hypothesis that the resetting of the name
+    resolution context below is not necessary at all since the list of local
+    tables for INSERT always consists of one table.
+  */
+  DBUG_ASSERT(!table_list->next_local);
+  DBUG_ASSERT(!context->table_list->next_local);
+  DBUG_ASSERT(!context->first_name_resolution_table->next_name_resolution_table);
+
   /* Save the state of the current name resolution context. */
   ctx_state.save_state(context, table_list);
 

sql/sql_parse.cc

@@ -3344,8 +3344,6 @@ end_with_restore_list:
     DBUG_ASSERT(first_table == all_tables && first_table != 0);
     if ((res= insert_precheck(thd, all_tables)))
       break;
-    /* Skip first table, which is the table we are inserting in */
-    select_lex->context.table_list= first_table->next_local;
 
     if (!thd->locked_tables &&
         !(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))