wrong results for some index merge join situations

[lzmhhh123]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

CREATE TABLE `admin_role_has_permissions` (
  `permission_id` bigint(20) unsigned NOT NULL,
  `role_id` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`permission_id`,`role_id`),
  KEY `admin_role_has_permissions_role_id_foreign` (`role_id`)
)

CREATE TABLE `admin_roles` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL COMMENT '角色名称',
  `created_at` timestamp NULL DEFAULT NULL,
  `updated_at` timestamp NULL DEFAULT NULL,
  PRIMARY KEY (`id`)
)

INSERT INTO `admin_roles` (`id`, `name`, `created_at`, `updated_at`) VALUES(1, 'admin','2020-04-27 02:40:03', '2020-04-27 02:40:03'),(2, 'developer','2020-04-27 02:40:03', '2020-04-27 02:40:03'),(3, 'analyst','2020-04-27 02:40:03', '2020-04-27 02:40:03'),(4, 'channel_admin','2020-04-27 02:40:03', '2020-04-27 02:40:03'),(5, 'test','2020-04-27 02:40:08', '2020-04-27 02:40:08');

INSERT INTO `admin_role_has_permissions` (`permission_id`, `role_id`) VALUES(1, 1),(2, 1),(3, 1),(4, 1),(5, 1),(6, 1),(7, 1),(8, 1),(9, 1),(10, 1),(11, 1),(12, 1),(13, 1),(14, 1),(15, 1),(16, 1),(17, 1),(18, 1),(19, 1),(20, 1),(21, 1),(22, 1),(23, 1),(24, 1),(25, 1),(26, 1),(27, 1),(28, 1),(29, 1),(30, 1),(31, 1),(32, 1),(33, 1),(34, 1),(35, 1),(36, 1),(37, 1),(38, 1),(39, 1),(40, 1),(41, 1),(42, 1),(43, 1),(44, 1),(45, 1),(46, 1),(47, 1),(48, 1),(49, 1),(50, 1),(51, 1),(52, 1),(53, 1),(54, 1),(55, 1),(56, 1),(57, 1),(58, 1),(59, 1),(60, 1),(61, 1),(62, 1),(63, 1),(64, 1),(65, 1),(66, 1),(67, 1),(68, 1),(69, 1),(70, 1),(71, 1),(72, 1),(73, 1),(74, 1),(75, 1),(76, 1),(77, 1),(78, 1),(79, 1),(80, 1),(81, 1),(82, 1),(83, 1),(5, 4),(6, 4),(7, 4),(84, 5),(85, 5),(86, 5);

SELECT /*+ inl_merge_join(admin_role_has_permissions) */ `admin_roles`.* FROM `admin_roles` INNER JOIN `admin_role_has_permissions` ON `admin_roles`.`id` = `admin_role_has_permissions`.`role_id` WHERE `admin_role_has_permissions`.`permission_id`
 IN (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67);

2. What did you expect to see?

The results for the query have 70 rows.

3. What did you see instead?

But the results only have 8 rows.

4. What version of TiDB are you using? (tidb-server -V or run select tidb_version(); on TiDB)

v4.0.0-rc and master

[lzmhhh123]

The problem is caused by the planner, the join keys of index merge join must strictly meet the prefix of the inner index. In this case, the join key is:

admin_role_has_permissions.role_id

And index used:

(permission_id, role_id)

The data read from the inner to keep order is not actually ordered by the join key, which causes the index merge join to produce the wrong join result.

[ChenPeng2013]

verified on
master: v4.0.0-beta.2-632-g6c305e2a4
release-4.0: v4.0.0-66-gcf781a347