Partition table couldn't generate IndexReader with UnionScan

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE `t` (
  `a` int(11) NOT NULL,
  `b` int(11) DEFAULT NULL,
  PRIMARY KEY (`a`) /*T![clustered_index] CLUSTERED */,
  KEY `idx1` (`b`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
PARTITION BY HASH (`a`) PARTITIONS 5;
begin;
insert into t values (1, 2);
explain select b from t use index(idx1) where b > 1;

2. What did you expect to see? (Required)

mysql> explain  select b from t use index(idx1) where b > 1;
+----------------------------+---------+-----------+------------------------+------------------------------------------------+
| id                         | estRows | task      | access object          | operator info                                  |
+----------------------------+---------+-----------+------------------------+------------------------------------------------+
| Projection_5               | 3333.33 | root      |                        | test.t.b                                       |
| └─UnionScan_6              | 3333.33 | root      |                        | gt(test.t.b, 1)                                |
|   └─IndexReader_8          | 3333.33 | root      | partition:all          | index:IndexRangeScan_7                         |
|     └─IndexRangeScan_7     | 3333.33 | cop[tikv] | table:t, index:idx1(b) | range:(1,+inf], keep order:false, stats:pseudo |
+----------------------------+---------+-----------+------------------------+------------------------------------------------+
4 rows in set (0.01 sec)

3. What did you see instead (Required)

mysql> explain  select b from t use index(idx1) where b > 1;
+-----------------------------------+---------+-----------+------------------------+------------------------------------------------+
| id                                | estRows | task      | access object          | operator info                                  |
+-----------------------------------+---------+-----------+------------------------+------------------------------------------------+
| Projection_5                      | 3333.33 | root      |                        | test.t.b                                       |
| └─UnionScan_6                     | 3333.33 | root      |                        | gt(test.t.b, 1)                                |
|   └─IndexLookUp_9                 | 3333.33 | root      | partition:all          |                                                |
|     ├─IndexRangeScan_7(Build)     | 3333.33 | cop[tikv] | table:t, index:idx1(b) | range:(1,+inf], keep order:false, stats:pseudo |
|     └─TableRowIDScan_8(Probe)     | 3333.33 | cop[tikv] | table:t                | keep order:false, stats:pseudo                 |
+-----------------------------------+---------+-----------+------------------------+------------------------------------------------+
5 rows in set (25.71 sec)

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                           |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v8.0.0-alpha-672-g693ed4e889
Edition: Community
Git Commit Hash: 693ed4e889e64bcaf741cd001cb90fb498775e39
Git Branch: master
UTC Build Time: 2024-03-29 09:17:29
GoVersion: go1.21.5
Race Enabled: false
Check Table Before Drop: false
Store: unistore |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

The problem is that we added one more column to the dataSource. It works fine when this line is commented.

tidb/pkg/planner/core/logical_plan_builder.go

Line 5075 in 8bba826

_ = ds.AddExtraPhysTblIDColumn()