Update foreign key handling to be smarter around when to skip foreign key emulation

[arthurschreiber]

Description

This improves the foreign key implementation by being more clever about when we can push down foreign key handling to MySQL and when we need to handle things on the vtgate side.

We can completely push down foreign key handling to MySQL for queries that involve foreign keys if all the foreign keys match the following conditions:

• referential action is RESTRICT (or none has been specified).
• foreign keys do not go across different keyspaces
• foreign keys are shard-local for sharded keyspaces

Related Issue(s)

N/A

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

• Apply the release notes (needs details) label if users need to know about this change.
• New features should be documented.
• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

New flags

• Is this flag really necessary?
• Flag names must be clear and intuitive, use dashes (-), and have a clear help text.

If a workflow is added or modified:

• Each item in Jobs should be named in order to mark it as required.
• If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

❌ Patch coverage is 96.22642% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.50%. Comparing base (8236f03) to head (874b6b3).
⚠️ Report is 97 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtgate/planbuilder/update.go	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18618      +/-   ##
==========================================
- Coverage   67.52%   67.50%   -0.02%     
==========================================
  Files        1608     1608              
  Lines      263611   263656      +45     
==========================================
- Hits       177994   177988       -6     
- Misses      85617    85668      +51     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[harshit-gangal]

The changes looks good.
We should add some self referential fuzzer testing scenario in e2e test.

[mattlord]

Seems reasonable to me, although I'm not sure why we can't passthrough regardless of the action type.

@arthurschreiber please create a feature/enhancement request and link it to this PR. It doesn't have to be much, but describing what the desired improvement is and the use case (you largely did this in the PR description).

Thanks!

[mattlord]

Why do we care about this part if it's scoped to 1 shard?

[mattlord]

I guess because we need to know about all changes made...

[github-actions]

This PR is being marked as stale because it has been open for 30 days with no activity. To rectify, you may do any of the following:

• Push additional commits to the associated branch.
• Remove the stale label.
• Add a comment indicating why it is not stale.

If no action is taken within 7 days, this PR will be closed.