MDEV-33525: Recreate/reuse temporary table

Calling a stored function that uses a cursor inside its body
could produce the error ER_NO_SUCH_TABLE on the second execution
in case the cursor uses multi-table query and one of the tables
is a temporary table just created before querying the cursor and
dropped just after the query has been executed.

The reason for issue is that re-parsing of failed a SP instruction
caused be create/drop of the temporary table used LEX object
left from previous parsing of a SP instruction's query instead
re-initialize the lex object before parsing.

To fix the issue, add initialization of lex for cursor's
statement before re-parsing the query of a failed SP instruction.

mysql-test/main/sp_validation.result

@@ -1965,4 +1965,32 @@ b
 2
 3
 DROP TABLE t1, t2;
+#
+# MDEV-33525: Recreate/reuse temporary table
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1);
+CREATE FUNCTION f1()
+RETURNS INT
+BEGIN
+DECLARE res INT;
+DECLARE t1_cur CURSOR FOR SELECT 100 FROM t1, t1_tmp;
+CREATE TEMPORARY TABLE t1_tmp SELECT 1 a;
+OPEN t1_cur;
+CLOSE t1_cur;
+DROP TEMPORARY TABLE t1_tmp;
+RETURN 0;
+END
+|
+SELECT f1();
+f1()
+0
+# Without the patch, the second call of f1 would result in error:
+#   ER_NO_SUCH_TABLE (1146): Table 'test.t1' doesn't exist
+SELECT f1();
+f1()
+0
+# Clean up
+DROP FUNCTION f1;
+DROP TABLE t1;
 SET sql_mode = default;

mysql-test/main/sp_validation.test

@@ -2760,5 +2760,40 @@ SELECT * FROM t2;
 
 DROP TABLE t1, t2;
 
+--echo #
+--echo # MDEV-33525: Recreate/reuse temporary table
+--echo #
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1);
+
+--delimiter |
+CREATE FUNCTION f1()
+RETURNS INT
+BEGIN
+  DECLARE res INT;
+
+  DECLARE t1_cur CURSOR FOR SELECT 100 FROM t1, t1_tmp;
+
+  CREATE TEMPORARY TABLE t1_tmp SELECT 1 a;
+
+  OPEN t1_cur;
+  CLOSE t1_cur;
+
+  DROP TEMPORARY TABLE t1_tmp;
+
+  RETURN 0;
+END
+|
+
+--delimiter ;
+SELECT f1();
+--echo # Without the patch, the second call of f1 would result in error:
+--echo #   ER_NO_SUCH_TABLE (1146): Table 'test.t1' doesn't exist
+SELECT f1();
+
+--echo # Clean up
+DROP FUNCTION f1;
+DROP TABLE t1;
+
 SET sql_mode = default;
 --enable_ps2_protocol

sql/sp_instr.cc

@@ -754,6 +754,7 @@ LEX* sp_lex_instr::parse_expr(THD *thd, sp_head *sp, LEX *sp_instr_lex)
     cleanup_items(cursor_lex->free_list);
     cursor_free_list= &cursor_lex->free_list;
     DBUG_ASSERT(thd->lex == sp_instr_lex);
+    lex_start(thd);
   }
 
   thd->lex->sphead= sp;