Add pushdown on inner join that equals should not be null

[Ulimo]

this should help performance if one is joining columns that contains null

[Copilot]

Pull Request Overview

This PR enhances inner join performance by adding pushdown filters to ensure join columns, when compared for equality, are not null. Key changes include updating the Check method in MergeJoinFindVisitor to be internal static for broader reuse, adding left/right pushdown conditions based on IS NOT NULL checks, and refactoring filter relation creation in JoinFilterPushdownVisitor.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/FlowtideDotNet.Core/Optimizer/MergeJoinFindVisitor.cs	Updated Check method accessibility to internal static to enable reuse
src/FlowtideDotNet.Core/Optimizer/FIlterPushdown/JoinFilterPushdownVisitor.cs	Added pushdown logic for inner join keys and refactored filter relation construction

Comments suppressed due to low confidence (2)

src/FlowtideDotNet.Core/Optimizer/FIlterPushdown/JoinFilterPushdownVisitor.cs:105

• [nitpick] Modifying the collection while iterating can be error-prone; consider building a new collection with the filtered expressions to improve readability and reduce potential iteration issues.

andFunctionScalar.Arguments.RemoveAt(i);

src/FlowtideDotNet.Core/Optimizer/MergeJoinFindVisitor.cs:22

• [nitpick] Changing the Check method to internal static improves reusability; please ensure this complies with overall design considerations, including any potential thread safety concerns.

internal static bool Check(JoinRelation joinRelation, Expression? expression, [NotNullWhen(true)] out DirectFieldReference? leftKey, [NotNullWhen(true)] out DirectFieldReference? rightKey)

[github-actions]

Benchmark

Benchmark suite	Current: 94974e0	Previous: 22d4209	Ratio
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.InnerJoin	310335266.6666667 ns (± 5560519.379518428)	458826533.3333333 ns (± 10640413.19005047)	0.68
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.LeftJoin	497183170 ns (± 15587112.692794932)	564994640 ns (± 28550338.329818636)	0.88
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.ProjectionAndNormalization	147668030 ns (± 12749678.858182184)	169842820 ns (± 7144067.768715523)	0.87
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.SumAggregation	155192116.66666666 ns (± 4220818.031791941)	171581250 ns (± 12415362.812660772)	0.90
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.ListAggWithMapAggregation	1858048100 ns (± 91553618.50820899)	1982296640 ns (± 123349811.75190067)	0.94
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.WindowSum	359827280 ns (± 11920569.255031405)
FlowtideDotNet.Benchmarks.Stream.StreamBenchmark.ListAggWithStructAggregation	1479757100 ns (± 77255673.9240412)

This comment was automatically generated by workflow using github-action-benchmark.