Add closure resolution benchmark

benchmarks/EntityFrameworkCore.Projectables.Benchmarks/ClosureCaptureBenchmark.cs

@@ -0,0 +1,198 @@
+using System.Linq.Expressions;
+using BenchmarkDotNet.Attributes;
+using EntityFrameworkCore.Projectables.Benchmarks.Helpers;
+using EntityFrameworkCore.Projectables.Services;
+using Microsoft.EntityFrameworkCore;
+
+namespace EntityFrameworkCore.Projectables.Benchmarks
+{
+    /// <summary>
+    /// Benchmarks two closure-capture scenarios that exercise
+    /// <c>ProjectableExpressionReplacer.VisitMember</c>:
+    ///
+    /// <list type="bullet">
+    ///   <item>
+    ///     <term>Value closure</term>
+    ///     <description>
+    ///       A local <c>int</c> is captured per iteration (<c>delta = i % 10</c>).
+    ///       In Full mode, <c>VisitMember</c> evaluates the closure field on <b>every</b>
+    ///       query execution to check whether it is an inlinable <c>IQueryable</c>.
+    ///       Previously this used <c>Expression.Lambda(...).Compile().Invoke()</c>
+    ///       (one JIT compilation per field per iteration); now it uses
+    ///       <c>FieldInfo.GetValue()</c> which is significantly cheaper.
+    ///     </description>
+    ///   </item>
+    ///   <item>
+    ///     <term>Sub-query closure</term>
+    ///     <description>
+    ///       An <c>IQueryable</c> sub-query is captured in a closure and inlined into
+    ///       the outer query at expansion time.  Full mode pays this cost on every
+    ///       iteration; Limited mode pays it only on the first EF Core cache miss.
+    ///     </description>
+    ///   </item>
+    /// </list>
+    ///
+    /// <para>
+    ///   Three benchmark groups are provided, from least to most accurate:
+    ///   <list type="number">
+    ///     <item><c>*_ValueClosure</c> / <c>*_SubQueryClosure</c> — end-to-end via
+    ///       <c>ToQueryString()</c> (includes EF Core cache lookup + SQL formatting)</item>
+    ///     <item><c>Isolated_Replace_*</c> — calls <c>ProjectableExpressionReplacer.Replace()</c>
+    ///       directly with a pre-built expression tree; zero EF Core pipeline overhead</item>
+    ///   </list>
+    /// </para>
+    ///
+    /// Run with:
+    /// <code>dotnet run -c Release -- --filter "*ClosureCapture*"</code>
+    /// </summary>
+    [MemoryDiagnoser]
+    public class ClosureCaptureBenchmark
+    {
+        // ── DbContexts — created once in GlobalSetup, NOT per benchmark invocation ──
+        // The original benchmark constructed a new TestDbContext inside each benchmark
+        // method, adding ~N ms of DI/EF startup noise to every invocation.
+        private TestDbContext _ctxBaseline = null!;
+        private TestDbContext _ctxFull     = null!;
+        private TestDbContext _ctxLimited  = null!;
+
+        // ── Sub-queries for Scenario B ────────────────────────────────────────
+        // Stored as fields so DbContext lifetime is controlled by GlobalSetup/Cleanup.
+        // Each benchmark method re-captures them into a *local variable* so the C#
+        // compiler generates a <>c__DisplayClass closure — the exact type that
+        // VisitMember checks for (NestedPrivate + CompilerGenerated).
+        // Capturing a field directly would embed 'this' instead and skip the code path.
+        private IQueryable<TestEntity> _subBaseline = null!;
+        private IQueryable<TestEntity> _subFull     = null!;
+        private IQueryable<TestEntity> _subLimited  = null!;
+
+        // ── Replacer + pre-built trees for isolated benchmarks ────────────────
+        // The isolated benchmarks call Replace() directly, bypassing:
+        //   • EF Core compiled-query cache lookup
+        //   • SQL generation and string formatting
+        //   • ParameterExtractingExpressionVisitor
+        // This isolates the pure expression-tree-rewrite cost.
+        private ProjectableExpressionReplacer _replacer      = null!;
+        private Expression                    _valueClosureExpr  = null!;
+        private Expression                    _subQueryExpr      = null!;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            _ctxBaseline = new TestDbContext(false);
+            _ctxFull     = new TestDbContext(true, useFullCompatibiltyMode: true);
+            _ctxLimited  = new TestDbContext(true, useFullCompatibiltyMode: false);
+
+            _subBaseline = _ctxBaseline.Entities.Where(x => x.Id > 5);
+            _subFull     = _ctxFull.Entities.Where(x => x.IdPlus1 > 5);
+            _subLimited  = _ctxLimited.Entities.Where(x => x.IdPlus1 > 5);
+
+            // Build expression trees used by the isolated benchmarks.
+            // Using local captures so the compiler generates the <>c__DisplayClass
+            // closures that VisitMember expects.
+            var delta = 5;
+            _valueClosureExpr = _ctxFull.Entities.Select(e => e.IdPlusDelta(delta)).Expression;
+
+            var sub = _ctxFull.Entities.Where(x => x.IdPlus1 > 5);
+            _subQueryExpr = _ctxFull.Entities.Where(e => sub.Any(s => s.Id == e.Id)).Expression;
+
+            _replacer = new ProjectableExpressionReplacer(new ProjectionExpressionResolver(), trackByDefault: false);
+        }
+
+        [GlobalCleanup]
+        public void Cleanup()
+        {
+            _ctxBaseline.Dispose();
+            _ctxFull.Dispose();
+            _ctxLimited.Dispose();
+        }
+
+        // ── Scenario A: value closure (int captured per call) ─────────────────
+        // A fixed delta=5 is used so the EF Core compiled-query cache is warm after
+        // BDN's own warmup phase.  All results are then per-single-query overhead,
+        // directly comparable with the Isolated_Replace_* µs numbers below.
+
+        /// <summary>Baseline: no projectables, int closure captured per call.</summary>
+        [Benchmark(Baseline = true)]
+        public string Baseline_ValueClosure()
+        {
+            var delta = 5;
+            return _ctxBaseline.Entities.Select(e => e.Id + delta).ToQueryString();
+        }
+
+        /// <summary>
+        /// Full mode: projectable method call with a closure-captured int argument.
+        /// <c>VisitMember</c> evaluates the 'delta' field via reflection on every call.
+        /// </summary>
+        [Benchmark]
+        public string Full_ValueClosure()
+        {
+            var delta = 5;
+            return _ctxFull.Entities.Select(e => e.IdPlusDelta(delta)).ToQueryString();
+        }
+
+        /// <summary>
+        /// Limited mode: expansion runs only on EF Core cache miss (first call per
+        /// query shape); per-call closure evaluation overhead is near zero.
+        /// </summary>
+        [Benchmark]
+        public string Limited_ValueClosure()
+        {
+            var delta = 5;
+            return _ctxLimited.Entities.Select(e => e.IdPlusDelta(delta)).ToQueryString();
+        }
+
+        // ── Scenario B: IQueryable sub-query closure ──────────────────────────
+
+        /// <summary>Baseline: no projectables, sub-IQueryable captured in a closure.</summary>
+        [Benchmark]
+        public string Baseline_SubQueryClosure()
+        {
+            var sub = _subBaseline;
+            return _ctxBaseline.Entities.Where(e => sub.Any(s => s.Id == e.Id)).ToQueryString();
+        }
+
+        /// <summary>
+        /// Full mode: sub-IQueryable captured in a closure; the sub-query itself uses
+        /// a projectable property so both the inlining path and the projectable
+        /// expansion path are exercised on every call.
+        /// </summary>
+        [Benchmark]
+        public string Full_SubQueryClosure()
+        {
+            var sub = _subFull;
+            return _ctxFull.Entities.Where(e => sub.Any(s => s.Id == e.Id)).ToQueryString();
+        }
+
+        /// <summary>
+        /// Limited mode: expansion occurs only on the first EF Core cache miss;
+        /// subsequent calls hit the compiled-query cache directly.
+        /// </summary>
+        [Benchmark]
+        public string Limited_SubQueryClosure()
+        {
+            var sub = _subLimited;
+            return _ctxLimited.Entities.Where(e => sub.Any(s => s.Id == e.Id)).ToQueryString();
+        }
+
+        // ── Isolated: pure ProjectableExpressionReplacer.Replace() cost ───────
+        // No EF Core pipeline. No SQL generation. No string formatting.
+        // Now on the same µs scale as the ToQueryString benchmarks above, so you
+        // can directly subtract to get: EF Core pipeline cost = Full_* − Isolated_Replace_*
+
+        /// <summary>
+        /// Pure replacer cost for a value-closure query (no EF Core involved).
+        /// </summary>
+        [Benchmark]
+        public Expression Isolated_Replace_ValueClosure()
+            => _replacer.Replace(_valueClosureExpr);
+
+        /// <summary>
+        /// Pure replacer cost for a sub-query-closure query, including the recursive
+        /// visit of the inlined sub-query expression (no EF Core involved).
+        /// </summary>
+        [Benchmark]
+        public Expression Isolated_Replace_SubQueryClosure()
+            => _replacer.Replace(_subQueryExpr);
+    }
+}
+