planner: fix possible inconsistent output cols among union's children (#48775)

[winoros]

This is a manual pick.

What problem does this PR solve?

Issue Number: close #48755

Problem Summary:

When UNIONALL's first child, it's possible that the selection is pushed at a position different with other children. This will cause inconsistent output columns among its children.

You can check the changed codes together with https://github.com/pingcap/tidb/blob/master/pkg/planner/core/rule_predicate_push_down.go#L479-L483 for more details.

And the failed case is something like Proj{c1}->UnionAll{c1, c2, c3}->(Select{c2 > 0, c3 > 0}->Proj{c1, c2, c3}, Proj{c1, c2, c3}->Select{c2>0, c3>0}).
UnionALL first only keeps the col c1. But its first child's selection also requires c2 and c3, so the projection of its first children will keep c2 and c3. The second child's projection doesn't need the c2 and c3 since the selection is pushed down.

What is changed and how it works?

We use the UNIONALL's self output columns to do the alignment.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Fix the potential execution failure when UNION ALL's first child is TableDual

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, time-and-fate

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [AilinKid,time-and-fate]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-11-24 13:36:09.249116588 +0000 UTC m=+584197.914342785: ☑️ agreed by AilinKid.
• 2023-11-24 14:06:20.409841719 +0000 UTC m=+586009.075067899: ☑️ agreed by time-and-fate.

[winoros]

/run-unit-test

[hawkingrei]

/test all

[tiprow]

@hawkingrei: No presubmit jobs available for pingcap/[email protected]

In response to this:

/test all

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[purelind]

/test ?

[ti-chi-bot]

@purelind: The following commands are available to trigger required jobs:

• /test build
• /test check-dev
• /test check-dev2
• /test mysql-test
• /test unit-test

The following commands are available to trigger optional jobs:

• /test pull-br-integration-test

Use /test all to run the following jobs that were automatically triggered:

• pingcap/tidb/release-6.5/ghpr_build
• pingcap/tidb/release-6.5/ghpr_check
• pingcap/tidb/release-6.5/ghpr_check2
• pingcap/tidb/release-6.5/ghpr_mysql_test
• pingcap/tidb/release-6.5/ghpr_unit_test

In response to this:

/test ?

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[tiprow]

@purelind: No presubmit jobs available for pingcap/[email protected]

In response to this:

/test ?

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[hawkingrei]

/retest