MDEV-21616: Server crash when using "SET STATEMENT max_statement_time=0 FOR desc xxx" lead to collapse

Main select should be pushed first.

Author: sanja-byelkin

mysql-test/main/parser.result

@@ -1797,4 +1797,14 @@ select * from t2;
 ERROR HY000: Table 't2' was not locked with LOCK TABLES
 SET STATEMENT max_statement_time=900 FOR unlock tables;
 drop table t1, t2;
+#
+# MDEV-21616: Server crash when using
+# "SET STATEMENT max_statement_time=0 FOR desc xxx" lead to collapse
+#
+create table t1 (a int);
+SET STATEMENT max_statement_time=0 FOR desc t1;
+Field	Type	Null	Key	Default	Extra
+a	int(11)	YES		NULL	
+drop table t1;
+SET STATEMENT max_statement_time=0 FOR do 1;
 # End of 10.4 tests

mysql-test/main/parser.test

@@ -1565,4 +1565,14 @@ select * from t2;
 SET STATEMENT max_statement_time=900 FOR unlock tables;
 drop table t1, t2;
 
+--echo #
+--echo # MDEV-21616: Server crash when using
+--echo # "SET STATEMENT max_statement_time=0 FOR desc xxx" lead to collapse
+--echo #
+
+create table t1 (a int);
+SET STATEMENT max_statement_time=0 FOR desc t1;
+drop table t1;
+SET STATEMENT max_statement_time=0 FOR do 1;
+
 --echo # End of 10.4 tests

sql/sql_yacc.yy

@@ -13253,11 +13253,14 @@ do:
           {
             LEX *lex=Lex;
             lex->sql_command = SQLCOM_DO;
+            if (lex->main_select_push())
+              MYSQL_YYABORT;
             mysql_init_select(lex);
           }
           expr_list
           {
             Lex->insert_list= $3;
+            Lex->pop_select(); //main select
           }
         ;
 
@@ -14552,6 +14555,8 @@ describe:
           describe_command table_ident
           {
             LEX *lex= Lex;
+            if (lex->main_select_push())
+              MYSQL_YYABORT;
             mysql_init_select(lex);
             lex->current_select->parsing_place= SELECT_LIST;
             lex->sql_command= SQLCOM_SHOW_FIELDS;
@@ -14563,6 +14568,7 @@ describe:
           opt_describe_column
           {
             Select->parsing_place= NO_MATTER;
+            Lex->pop_select(); //main select
           }
         | describe_command opt_extended_describe
           { Lex->describe|= DESCRIBE_NORMAL; }