planner: generate PK filters prototype (wip)

[terry1purcell]

What problem does this PR solve?

Issue Number: ref #66297

This PR has the effect of taking the SQL from the issue - such as the following.
NOTE: There is an index on c, and another index on b - but no index on both columns (this is by design).

Explain select *
From t1
Where c = 5
Order by b
Limit 10;

And generating "lookup" subqueries to produce the min/max PK values related to another indexes filters. An example that demonstrates how these are internally rewritten appears here. This allows the ranges to apply as either a TableRangeScan (against the PK), or against the ORDER BY index as filters against the index (since a clustered PK is part of a secondary index):

Explain analyze select *
From t1
Where c = 5
And a >= (select min(a) from t1 where c = 5)
And a <= (select max(a) from t1 where c = 5)
Order by b
Limit 10;

In this PR - this is triggered by using a hint to specify the generation of the PK ranges, and which index to generate the subqueries on:

Explain select /*+ pk_filter(t1, ic) */ *
From t1
Where c = 5
Order by b
Limit 10;

Problem Summary:

What changed and how does it work?

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.

None

[pantheon-ai]

Posted PR review with 3 inline P2 comments: #66292 (review)

[ti-chi-bot]

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[tiprow]

Hi @terry1purcell. Thanks for your PR.

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[codecov]

Codecov Report

❌ Patch coverage is 69.08023% with 158 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.2551%. Comparing base (2f9776e) to head (ebcb52f).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #66292        +/-   ##
================================================
- Coverage   77.7002%   77.2551%   -0.4451%     
================================================
  Files          2006       1928        -78     
  Lines        548386     536430     -11956     
================================================
- Hits         426097     414420     -11677     
- Misses       120629     122002      +1373     
+ Partials       1660          8      -1652     

Flag	Coverage Δ
integration	41.4342% <63.2411%> (-6.7524%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	56.7974% <ø> (ø)
parser	∅ <ø> (∅)
br	48.7604% <ø> (-12.1132%)	⬇️

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[pantheon-ai]

P2: MIN/MAX subqueries lose equality predicates

The cloned DataSource for MIN/MAX subqueries loses its equality predicates during sub-optimization. The code re-runs optimization with predicate pushdown enabled, but DataSource.PredicatePushDown receives an empty predicates slice and overwrites ds.PushedDownConds, resulting in IndexFullScan instead of efficient range scans.

This causes 2 full secondary index scans per qualifying index (MIN + MAX), which can cause severe performance regressions on large tables.

Evidence: Integration test shows IndexFullScan without range predicates at tests/integrationtest/r/planner/core/casetest/rule/rule_generate_pk_filter.result:15. Root cause: empty predicates passed to DataSource.PredicatePushDown at pkg/planner/core/operator/logicalop/logical_datasource.go:175.

[pantheon-ai]

P2: DataSource filter state inconsistency

New PK filter predicates are appended only to PushedDownConds without updating AllConds. The ColumnPruner pass (which runs after this rule) only inspects AllConds to determine column usage, so it may incorrectly prune PK columns that are only referenced by the new predicates.

This can cause planner/executor errors when the predicates (containing ScalarSubQueryExpr) are evaluated and reference pruned columns.

Evidence: ds.PushedDownConds = append(ds.PushedDownConds, newConds...) here, but ColumnPruner only checks ds.AllConds at pkg/planner/core/operator/logicalop/logical_datasource.go:188.

[ti-chi-bot]

@terry1purcell: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-unit-test-next-gen	ebcb52f	link	true	/test pull-unit-test-next-gen
idc-jenkins-ci-tidb/unit-test	ebcb52f	link	true	/test unit-test

Full PR test history. Your PR dashboard.

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