MDEV-34649: Memory leaks on running DELETE statement in PS mode with positional parameters

Re-design of a way for handling the DELETE statement introduced by
the task MDEV-28883, added regression caused by missing reset of
the data member current_select->first_cond_optimization on handling
the DELETE statement that results in a memory leaks on second execution
of the same DELETE statement in PS mode.

To fix memory leaks, added set of the data member
  current_select->first_cond_optimization
to the value false on finishing execution of DELETE statement.

mysql-test/main/ps_mem_leaks.result

@@ -148,3 +148,17 @@ CALL p1(2);
 DROP TABLE t1;
 DROP PROCEDURE p1;
 # End of 10.11 tests
+#
+# MDEV-34649: Memory leaks on running DELETE statement in PS mode with positional parameters
+#
+CREATE TABLE t1 (a INT, b VARCHAR(30)) CHARSET=utf8mb4;
+INSERT INTO t1 VALUES (1, 'one'), (0, NULL), (3, 'three'), (4, 'four');
+PREPARE stmt FROM 'DELETE FROM t1 WHERE b=?' ;
+SET @arg00=NULL;
+EXECUTE stmt USING @arg00;
+SET @arg00='one';
+EXECUTE stmt USING @arg00;
+# Clean up
+DEALLOCATE PREPARE stmt;
+DROP TABLE t1;
+# End of 11.1

mysql-test/main/ps_mem_leaks.test

@@ -167,3 +167,21 @@ DROP TABLE t1;
 DROP PROCEDURE p1;
 
 --echo # End of 10.11 tests
+
+--echo #
+--echo # MDEV-34649: Memory leaks on running DELETE statement in PS mode with positional parameters
+--echo #
+CREATE TABLE t1 (a INT, b VARCHAR(30)) CHARSET=utf8mb4;
+INSERT INTO t1 VALUES (1, 'one'), (0, NULL), (3, 'three'), (4, 'four');
+PREPARE stmt FROM 'DELETE FROM t1 WHERE b=?' ;
+SET @arg00=NULL;
+EXECUTE stmt USING @arg00;
+SET @arg00='one';
+# Without the patch, attempt to run the same prepared statement the second time
+# would result in memory leaks
+EXECUTE stmt USING @arg00;
+--echo # Clean up
+DEALLOCATE PREPARE stmt;
+DROP TABLE t1;
+
+--echo # End of 11.1

sql/sql_delete.cc

@@ -912,6 +912,7 @@ bool Sql_cmd_delete::delete_from_single_table(THD *thd)
   {
     thd->lex->current_select->save_leaf_tables(thd);
     thd->lex->current_select->leaf_tables_saved= true;
+    thd->lex->current_select->first_cond_optimization= false;
   }
 
   delete deltempfile;