Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

planner: fix a panic during column pruning (#47883) #48810

Merged

Conversation

ti-chi-bot
Copy link
Member

This is an automated cherry-pick of #47883

What problem does this PR solve?

Issue Number: close #47331

Problem Summary:

What is changed and how it works?

Through my investigation, I identified several key points:

  1. The panic occurs during DeriveStats: p.StatsInfo().ColNDVs[selfSchema.Columns[i].UniqueID] = childProfile.RowCount.
  2. There's a discrepancy in the number of expressions and schema columns: the plan has 8 expressions but only 7 columns in the schema.
  3. The logic plan causing the panic is a projection (ID 25), generated by the joinReOrderSolver.
  4. Post-debugging, I noted that the schema undergoes changes after the LogicalProjection.PruneColumns process.
  5. On further debugging the PruneColumns function individually, I discovered that the schema of projection#25 is affected even before it's reached in the process.
  6. This led me to suspect a memory issue. Notably, projection#18 and projection#25 appear to share the same schema memory address (0x14006b557c0).
  7. Consequently, when a column is pruned from projection#18, projection#25 becomes corrupted, leading to a mismatch between expressions and columns.

So I cloned that schema and made sure we didn't have this kind of problem anymore.

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 a panic issue during column pruning

@ti-chi-bot ti-chi-bot added release-note Denotes a PR that will be considered when it comes time to generate release notes. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. type/cherry-pick-for-release-7.5 This PR is cherry-picked to release-7.5 from a source PR. labels Nov 22, 2023
@ti-chi-bot ti-chi-bot added the cherry-pick-approved Cherry pick PR approved by release team. label Nov 23, 2023
@ti-chi-bot ti-chi-bot bot added approved needs-1-more-lgtm Indicates a PR needs 1 more LGTM. labels Nov 23, 2023
@Rustin170506
Copy link
Member

/retest

Copy link

ti-chi-bot bot commented Nov 23, 2023

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, hi-rustin

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 [hawkingrei,hi-rustin]

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 ti-chi-bot bot added lgtm and removed needs-1-more-lgtm Indicates a PR needs 1 more LGTM. labels Nov 23, 2023
Copy link

ti-chi-bot bot commented Nov 23, 2023

[LGTM Timeline notifier]

Timeline:

  • 2023-11-23 10:09:20.770133526 +0000 UTC m=+485389.435359720: ☑️ agreed by hi-rustin.
  • 2023-11-23 10:09:55.201811194 +0000 UTC m=+485423.867037390: ☑️ agreed by hawkingrei.

@Rustin170506
Copy link
Member

/RETEST

@Rustin170506
Copy link
Member

/retest

@ti-chi-bot ti-chi-bot bot merged commit f38e741 into pingcap:release-7.5 Nov 23, 2023
7 checks passed
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
approved cherry-pick-approved Cherry pick PR approved by release team. lgtm release-note Denotes a PR that will be considered when it comes time to generate release notes. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. type/cherry-pick-for-release-7.5 This PR is cherry-picked to release-7.5 from a source PR.
Projects
None yet
Development

Successfully merging this pull request may close these issues.

3 participants