How does roslyn-linq-rewrite compare to LinqOptimizer?

roslyn-linq-rewrite performs compile-time optimizations by rewriting LINQ into procedural code, eliminating runtime expression trees and allocations, whereas LinqOptimizer does runtime optimizations. This makes it more efficient for static queries but less flexible for dynamic ones, and it avoids syntax changes like AsQueryExpr().Run().

How to install roslyn-linq-rewrite in a .NET Core project?

For older project.json projects, add the tool and compiler settings in project.json as per the README. For newer MSBuild-based projects, download binaries and set CscToolPath, then use dotnet restore and build. Integration may require adjustments for different .NET versions.

Can roslyn-linq-rewrite optimize Entity Framework queries?

No, it does not optimize IQueryable expressions, so Entity Framework queries that rely on IQueryable remain unchanged and unoptimized. The README explicitly states that IQueryable expressions are left intact.

What LINQ methods are supported by roslyn-linq-rewrite?

It supports common methods like Select, Where, ToList, Count, and others listed in the README, but excludes many advanced LINQ operations. Refer to the 'Supported LINQ methods' section for the full list, which is limited compared to standard LINQ.

Is roslyn-linq-rewrite compatible with async LINQ?

The README does not mention async support, and since it generates procedural loops, async LINQ methods are likely not optimized. This makes it less suitable for asynchronous codebases where async LINQ is prevalent.

How to exclude a method from optimization in roslyn-linq-rewrite?

Apply the [NoLinqRewrite] attribute to the method, as described in the README. This attribute prevents the compiler from optimizing that specific code, allowing fine-grained control over the optimization process.

Open-Awesome

roslyn-linq-rewrite

MITC#

A Roslyn-based compiler that rewrites LINQ expressions into procedural code to minimize allocations and dynamic dispatch in C#.

GitHub

714 stars28 forks0 contributors

What is roslyn-linq-rewrite?

roslyn-linq-rewrite is a custom C# compiler that rewrites LINQ expressions into optimized procedural code during the build process. It solves performance issues in LINQ-heavy applications by eliminating unnecessary memory allocations and dynamic dispatch overhead while maintaining the original LINQ syntax.

Target Audience

C# developers working on performance-critical applications who use LINQ extensively and want to reduce memory allocations without rewriting their code manually.

Value Proposition

Developers choose roslyn-linq-rewrite because it provides significant performance improvements to existing LINQ code without requiring syntax changes, offering build-time optimizations that outperform runtime solutions like LinqOptimizer.

Overview

Compiles C# code by first rewriting the syntax trees of LINQ expressions using plain procedural code, minimizing allocations and dynamic dispatch.

Use Cases

Best For

Optimizing LINQ-heavy C# applications for reduced memory allocations
Improving performance in game development or real-time systems using LINQ
Reducing garbage collection pressure in long-running .NET services
Maintaining LINQ syntax while achieving procedural code performance
Build-time optimization of existing codebases without refactoring
Performance-critical applications where enumerator allocations are problematic

Not Ideal For

Applications heavily dependent on IQueryable for ORM integrations like Entity Framework
Projects using Parallel LINQ (PLINQ) extensively
Teams working with F# or requiring full LINQ method coverage

Pros & Cons

Pros

Build-Time Optimization

Rewrites LINQ expressions during compilation, not at runtime, reducing overhead without syntax changes, as shown in the decompiled output example.

Significant Allocation Reduction

Minimizes object allocations by eliminating unnecessary enumerators, delegates, and closures, evidenced by the example where only the input array is allocated.

Procedural Code Efficiency

Transforms LINQ chains into optimized for/foreach loops, achieving near-handwritten performance while maintaining LINQ's declarative syntax.

Selective and Safe Optimization

Leaves non-optimizable call chains and IQueryable intact, preventing breaks, and allows exclusions with the [NoLinqRewrite] attribute for control.

Cons

Limited LINQ Method Support

Only optimizes a subset of LINQ methods; advanced operations like GroupBy or Join are not covered, restricting its usefulness for complex queries.

Complex Integration Setup

Requires manual configuration with MSBuild or project.json modifications, which can be error-prone and cumbersome compared to standard compilers.

Edge Case Handling Issues

The README acknowledges bugs with Min/Max and NaN values, indicating that some edge cases might not be correctly optimized or could introduce subtle bugs.

Frequently Asked Questions

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