fix(query): union all panic in mysql client

[zhyass]

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Summary

Fix panic bug in Union All due to incorrect output projection.

This PR addresses a panic issue that occurs when executing a Union All operation. The root cause of the bug was that the out project for Union All was not correctly set, leading to panic.

mysql> create table t1(a int, b int);
Query OK, 0 rows affected (0.18 sec)

mysql> insert into t1 values(1,1),(2,2);
+-------------------------+
| number of rows inserted |
+-------------------------+
|                       2 |
+-------------------------+
1 row in set (0.19 sec)
Read 2 rows, 18.00 B in 0.112 sec., 17.82 rows/sec., 160.42 B/sec.

mysql> create table t2(a int, b int);
Query OK, 0 rows affected (0.05 sec)

mysql> insert into t2 values(3,3),(4,4);
+-------------------------+
| number of rows inserted |
+-------------------------+
|                       2 |
+-------------------------+
1 row in set (0.22 sec)
Read 2 rows, 18.00 B in 0.123 sec., 16.27 rows/sec., 146.41 B/sec.

mysql> select a from (select a, b from t1 where a>1 union all select a, b from t2 where b<4);
+------+
| a    |
+------+
|    3 |
|    2 |
+------+
2 rows in set (0.21 sec)
Read 4 rows, 27.00 B in 0.076 sec., 52.64 rows/sec., 355.35 B/sec.

mysql> explain select a from (select a, b from t1 where a>1 union all select a, b from t2 where b<4);
+---------------------------------------------------------------------------------------------------------+
| explain                                                                                                 |
+---------------------------------------------------------------------------------------------------------+
| UnionAll                                                                                                |
| ├── output columns: [t1.a (#0)]                                                                         |
| ├── estimated rows: 2.00                                                                                |
| ├── Filter                                                                                              |
| │   ├── output columns: [t1.a (#0)]                                                                     |
| │   ├── filters: [is_true(t1.a (#0) > 1)]                                                               |
| │   ├── estimated rows: 1.00                                                                            |
| │   └── TableScan                                                                                       |
| │       ├── table: default.default.t1                                                                   |
| │       ├── output columns: [a (#0)]                                                                    |
| │       ├── read rows: 2                                                                                |
| │       ├── read size: < 1 KiB                                                                          |
| │       ├── partitions total: 1                                                                         |
| │       ├── partitions scanned: 1                                                                       |
| │       ├── pruning stats: [segments: <range pruning: 1 to 1>, blocks: <range pruning: 1 to 1>]         |
| │       ├── push downs: [filters: [is_true(t1.a (#0) > 1)], limit: NONE]                                |
| │       └── estimated rows: 2.00                                                                        |
| └── Filter                                                                                              |
|     ├── output columns: [t2.a (#2)]                                                                     |
|     ├── filters: [is_true(t2.b (#3) < 4)]                                                               |
|     ├── estimated rows: 1.00                                                                            |
|     └── TableScan                                                                                       |
|         ├── table: default.default.t2                                                                   |
|         ├── output columns: [a (#2), b (#3)]                                                            |
|         ├── read rows: 2                                                                                |
|         ├── read size: < 1 KiB                                                                          |
|         ├── partitions total: 1                                                                         |
|         ├── partitions scanned: 1                                                                       |
|         ├── pruning stats: [segments: <range pruning: 1 to 1>, blocks: <range pruning: 1 to 1>]         |
|         ├── push downs: [filters: [is_true(t2.b (#3) < 4)], limit: NONE]                                |
|         └── estimated rows: 2.00                                                                        |
+---------------------------------------------------------------------------------------------------------+
31 rows in set (0.13 sec)
Read 0 rows, 0.00 B in 0.017 sec., 0 rows/sec., 0.00 B/sec.

• fixes: bug: union all panic in mysql client #17085

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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