MDEV-15336 Server crashes in handler::print_error / ha_partition::print_error upon query timeout

set m_last_part to something meaningful when opening partitions

mysql-test/suite/parts/r/print_error.result

+CREATE TABLE t1 (i INT) ENGINE=InnoDB PARTITION BY HASH (i) PARTITIONS 2;
+XA START 'xid';
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+connect  con1,localhost,root,,test;
+CREATE TABLE t2 SELECT * FROM t1;;
+connect  con2,localhost,root,,test;
+SET max_statement_time= 1;
+DELETE FROM t1 PARTITION (p1) ORDER BY i LIMIT 2;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+disconnect con2;
+connection default;
+XA END 'xid';
+XA ROLLBACK 'xid';
+connection con1;
+disconnect con1;
+connection default;
+call mtr.add_suppression('Sort aborted');
+DROP TABLE IF EXISTS t2, t1;

mysql-test/suite/parts/t/print_error.test

+#
+# MDEV-15336 Server crashes in handler::print_error / ha_partition::print_error upon query timeout
+#
+--source include/have_innodb.inc
+--source include/have_partition.inc
+
+CREATE TABLE t1 (i INT) ENGINE=InnoDB PARTITION BY HASH (i) PARTITIONS 2;
+XA START 'xid';
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+
+--connect (con1,localhost,root,,test)
+--send CREATE TABLE t2 SELECT * FROM t1;
+
+--connect (con2,localhost,root,,test)
+SET max_statement_time= 1;
+--error ER_STATEMENT_TIMEOUT
+DELETE FROM t1 PARTITION (p1) ORDER BY i LIMIT 2;
+
+# Cleanup
+--disconnect con2
+--connection default
+XA END 'xid';
+XA ROLLBACK 'xid';
+--connection con1
+--reap
+--disconnect con1
+--connection default
+call mtr.add_suppression('Sort aborted');
+DROP TABLE IF EXISTS t2, t1;

sql/ha_partition.cc

@@ -8383,6 +8383,7 @@ int ha_partition::open_read_partitions(char *name_buff, size_t name_buff_size)
       if (error)
         goto err_handler;
       bitmap_set_bit(&m_opened_partitions, n_file);
+      m_last_part= n_file;
     }
     if (!m_file_sample && should_be_open)
       m_file_sample= *file;