Allow runtime constants in precompiled queries#38430
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Improves performance by moving GetBytes call to query compile time instead of shaper runtime. Quick benchmark: https://gist.github.com/JoasE/47ed25296fe8651825e358c57454b44c
JoasE
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Pull request overview
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Copilot was unable to run its full agentic suite in this review.
Adds support for “runtime constants” during precompiled query code generation so that certain computed constants (e.g., UTF8 byte arrays for JSON property names) are emitted as static fields initialized at runtime instead of being embedded directly into generated code.
Changes:
- Introduce
RuntimeConstantExpressionandRuntimeConstantProcessorto capture and rewrite runtime-constant nodes. - Update relational shaper processing to wrap
Encoding.UTF8.GetBytes(...)for JSON property-name comparisons in runtime constants. - Extend precompiled query code generation and translator name-uniquification, and add coverage in design/relational/SQL Server tests.
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| test/EFCore.SqlServer.FunctionalTests/Query/PrecompiledQuerySqlServerTest.cs | Adds provider-specific SQL assertion for the new runtime-constant JSON shaper scenario. |
| test/EFCore.Relational.Specification.Tests/Query/PrecompiledQueryRelationalTestBase.cs | Adds a relational test validating runtime constant emission for UTF8 byte arrays in generated code. |
| test/EFCore.Design.Tests/Query/LinqToCSharpSyntaxTranslatorTest.cs | Adds a regression test for variable renaming when a constant replacement would conflict. |
| src/EFCore/Query/RuntimeConstantProcessor.cs | New processor that collects runtime constants and rewrites them to constants during visiting. |
| src/EFCore/Query/RuntimeConstantExpression.cs | New expression node representing a runtime-initialized constant. |
| src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.ShaperProcessingExpressionVisitor.cs | Wraps JSON property-name UTF8 byte generation in runtime constants. |
| src/EFCore.Design/Query/Internal/PrecompiledQueryCodeGenerator.cs | Collects runtime constants, emits them as static fields, and passes constant replacements into translation. |
| src/EFCore.Design/Query/Internal/LinqToCSharpSyntaxTranslator.cs | Avoids variable-name collisions with constant replacement identifiers. |
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| if (parameterNames.Contains(name) || _liftedState.VariableNames.Contains(name) || _constantReplacements?.Values.Contains(name) == true) | ||
| { | ||
| var baseName = name; | ||
| for (var j = isUnnamed ? _unnamedParameterCounter++ : 0; | ||
| parameterNames.Contains(name) || _liftedState.VariableNames.Contains(name); | ||
| parameterNames.Contains(name) || _liftedState.VariableNames.Contains(name) || _constantReplacements?.Values.Contains(name) == true; | ||
| j++) |
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I was thinking this is ok for code generation, since it's not a hot path?
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Adds support for storing values which don't change across executions of the query in precompiled queries as a private static readonly field. Also allowing non-precompiled queries to use a ConstantExpression directly for these values.
Improves performance by moving GetBytes call to query compile time instead of shaper runtime.