cached-command should use a backing pool, in particular for async APIs (#150)

mgravell · web-flow · commit 4957352acbd0 · 2025-03-27T16:12:13.000Z
diff --git a/src/Dapper.AOT.Analyzers/CodeAnalysis/DapperInterceptorGenerator.cs b/src/Dapper.AOT.Analyzers/CodeAnalysis/DapperInterceptorGenerator.cs
@@ -579,30 +579,34 @@ private static void WriteCommandFactory(in GenerateState ctx, string baseFactory
             if (additionalCommandState is not null && additionalCommandState.HasCommandProperties)
             {
                 sb.Indent()
-                    .NewLine().Append("var cmd = TryReuse(ref Storage, sql, commandType, args);")
+                    .NewLine().Append("var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);")
                     .NewLine().Append("if (cmd is null)").Indent()
                     .NewLine().Append("cmd = base.GetCommand(connection, sql, commandType, args);");
                 WriteCommandProperties(ctx, sb, "cmd", additionalCommandState.CommandProperties);
                 sb.Outdent().NewLine().Append("return cmd;").Outdent();
             }
             else
             {
-                sb.Indent(false).NewLine().Append(" => TryReuse(ref Storage, sql, commandType, args) ?? base.GetCommand(connection, sql, commandType, args);").Outdent(false);
+                sb.Indent(false).NewLine().Append(" => TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool) ?? base.GetCommand(connection, sql, commandType, args);").Outdent(false);
             }
-            sb.NewLine().NewLine().Append("public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);").NewLine();
+            sb.NewLine().NewLine().Append("public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);").NewLine();
 
             if (cacheCount == 1)
             {
+                sb.Append("private static readonly DbCommandCache _cmdPool = new();").NewLine();
+                sb.Append("[global::System.ThreadStatic] // note this works correctly with ref").NewLine();
                 sb.Append("private static global::System.Data.Common.DbCommand? Storage;").NewLine();
             }
             else
             {
+                sb.Append("private readonly DbCommandCache _cmdPool = new(); // note: per cache instance").NewLine();
                 sb.Append("protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}").NewLine().NewLine();
 
                 for (int i = 0; i < cacheCount; i++)
                 {
                     sb.Append("internal sealed class Cached").Append(i).Append(" : CommandFactory").Append(index).Indent().NewLine()
                         .Append("protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;").NewLine()
+                        .Append("[global::System.ThreadStatic] // note this works correctly with ref-return").NewLine()
                         .Append("private static global::System.Data.Common.DbCommand? s_Storage;").NewLine()
                         .Outdent().NewLine();
                 }
diff --git a/src/Dapper.AOT/CommandFactory.cs b/src/Dapper.AOT/CommandFactory.cs
@@ -1,5 +1,6 @@
 ﻿using Dapper.Internal;
 using System;
+using System.Collections.Concurrent;
 using System.Data;
 using System.Data.Common;
 using System.Diagnostics;
@@ -175,12 +176,53 @@ protected static void SetValueWithDefaultSize(DbParameter parameter, string? val
     /// <summary>
     /// Provides an opportunity to recycle and reuse command instances
     /// </summary>
-    protected static bool TryRecycle(ref DbCommand? storage, DbCommand command)
+    protected static bool TryRecycleInterlocked(ref DbCommand? storage, DbCommand command, DbCommandCache? cache = null)
     {
         // detach and recycle
         command.Connection = null;
         command.Transaction = null;
-        return Interlocked.CompareExchange(ref storage, command, null) is null;
+        if (Interlocked.CompareExchange(ref storage, command, null) is null)
+        {
+            return true;
+        }
+        return cache is not null && cache.TryPut(command);
+    }
+
+    /// <summary>
+    /// Provides an opportunity to recycle and reuse command instances
+    /// </summary>
+    protected static bool TryRecycleThreadStatic(ref DbCommand? storage, DbCommand command, DbCommandCache? cache = null)
+    {
+        // detach and recycle
+        command.Connection = null;
+        command.Transaction = null;
+        if (storage is null)
+        {
+            storage = command;
+            return true;
+        }
+        return cache is not null && cache.TryPut(command);
+    }
+
+
+    /// <summary>
+    /// A simple store for command re-use.
+    /// </summary>
+    protected sealed class DbCommandCache(int capacity = 16)
+    {
+        private readonly ConcurrentQueue<DbCommand> store = [];
+        internal bool TryPut(DbCommand command)
+        {
+            if (store.Count < capacity) // not exact - inherent race condition
+            {
+                store.Enqueue(command);
+                return true;
+            }
+            return false;
+        }
+
+        internal DbCommand? TryTake()
+            => store.TryDequeue(out var cmd) ? cmd : null;
     }
 }
 
@@ -252,9 +294,26 @@ public virtual void UpdateParameters(in UnifiedCommand command, T args)
     /// <summary>
     /// Provides an opportunity to recycle and reuse command instances
     /// </summary>
-    protected DbCommand? TryReuse(ref DbCommand? storage, string sql, CommandType commandType, T args)
+    protected DbCommand? TryReuseThreadStatic(ref DbCommand? storage, string sql, CommandType commandType, T args, DbCommandCache? cache = null)
+    {
+        var cmd = storage ?? cache?.TryTake();
+        storage = null;
+        if (cmd is not null)
+        {
+            // try to avoid any dirty detection in the setters
+            if (cmd.CommandText != sql) cmd.CommandText = sql;
+            if (cmd.CommandType != commandType) cmd.CommandType = commandType;
+            UpdateParameters(new(cmd), args);
+        }
+        return cmd;
+    }
+
+    /// <summary>
+    /// Provides an opportunity to recycle and reuse command instances
+    /// </summary>
+    protected DbCommand? TryReuseInterlocked(ref DbCommand? storage, string sql, CommandType commandType, T args, DbCommandCache? cache = null)
     {
-        var cmd = Interlocked.Exchange(ref storage, null);
+        var cmd = Interlocked.Exchange(ref storage, null) ?? cache?.TryTake();
         if (cmd is not null)
         {
             // try to avoid any dirty detection in the setters
diff --git a/test/Dapper.AOT.Test/Interceptors/CacheCommand.output.cs b/test/Dapper.AOT.Test/Interceptors/CacheCommand.output.cs
@@ -118,20 +118,23 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
 
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
-                 => TryReuse(ref Storage, sql, commandType, args) ?? base.GetCommand(connection, sql, commandType, args);
+                 => TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool) ?? base.GetCommand(connection, sql, commandType, args);
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private readonly DbCommandCache _cmdPool = new(); // note: per cache instance
             protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}
 
             internal sealed class Cached0 : CommandFactory0
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
             internal sealed class Cached1 : CommandFactory0
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
@@ -165,9 +168,11 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
 
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
-                 => TryReuse(ref Storage, sql, commandType, args) ?? base.GetCommand(connection, sql, commandType, args);
+                 => TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool) ?? base.GetCommand(connection, sql, commandType, args);
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private static readonly DbCommandCache _cmdPool = new();
+            [global::System.ThreadStatic] // note this works correctly with ref
             private static global::System.Data.Common.DbCommand? Storage;
 
         }
diff --git a/test/Dapper.AOT.Test/Interceptors/CacheCommand.output.netfx.cs b/test/Dapper.AOT.Test/Interceptors/CacheCommand.output.netfx.cs
@@ -118,20 +118,23 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
 
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
-                 => TryReuse(ref Storage, sql, commandType, args) ?? base.GetCommand(connection, sql, commandType, args);
+                 => TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool) ?? base.GetCommand(connection, sql, commandType, args);
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private readonly DbCommandCache _cmdPool = new(); // note: per cache instance
             protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}
 
             internal sealed class Cached0 : CommandFactory0
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
             internal sealed class Cached1 : CommandFactory0
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
@@ -165,9 +168,11 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
 
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
-                 => TryReuse(ref Storage, sql, commandType, args) ?? base.GetCommand(connection, sql, commandType, args);
+                 => TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool) ?? base.GetCommand(connection, sql, commandType, args);
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private static readonly DbCommandCache _cmdPool = new();
+            [global::System.ThreadStatic] // note this works correctly with ref
             private static global::System.Data.Common.DbCommand? Storage;
 
         }
diff --git a/test/Dapper.AOT.Test/Interceptors/CommandProperties.output.cs b/test/Dapper.AOT.Test/Interceptors/CommandProperties.output.cs
@@ -199,7 +199,7 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
             {
-                var cmd = TryReuse(ref Storage, sql, commandType, args);
+                var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);
                 if (cmd is null)
                 {
                     cmd = base.GetCommand(connection, sql, commandType, args);
@@ -212,7 +212,9 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
                 return cmd;
             }
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private readonly DbCommandCache _cmdPool = new();
+            [global::System.ThreadStatic] // note this works correctly with ref
             private static global::System.Data.Common.DbCommand? Storage;
 
         }
@@ -256,7 +258,7 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
             {
-                var cmd = TryReuse(ref Storage, sql, commandType, args);
+                var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);
                 if (cmd is null)
                 {
                     cmd = base.GetCommand(connection, sql, commandType, args);
@@ -269,18 +271,21 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
                 return cmd;
             }
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private readonly DbCommandCache _cmdPool = new();
             protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}
 
             internal sealed class Cached0 : CommandFactory1
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
             internal sealed class Cached1 : CommandFactory1
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
diff --git a/test/Dapper.AOT.Test/Interceptors/CommandProperties.output.netfx.cs b/test/Dapper.AOT.Test/Interceptors/CommandProperties.output.netfx.cs
@@ -199,7 +199,7 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
             {
-                var cmd = TryReuse(ref Storage, sql, commandType, args);
+                var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);
                 if (cmd is null)
                 {
                     cmd = base.GetCommand(connection, sql, commandType, args);
@@ -212,7 +212,9 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
                 return cmd;
             }
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private readonly DbCommandCache _cmdPool = new();
+            [global::System.ThreadStatic] // note this works correctly with ref
             private static global::System.Data.Common.DbCommand? Storage;
 
         }
@@ -256,7 +258,7 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
             public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,
                 string sql, global::System.Data.CommandType commandType, object? args)
             {
-                var cmd = TryReuse(ref Storage, sql, commandType, args);
+                var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);
                 if (cmd is null)
                 {
                     cmd = base.GetCommand(connection, sql, commandType, args);
@@ -269,18 +271,21 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje
                 return cmd;
             }
 
-            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);
+            public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);
+            private readonly DbCommandCache _cmdPool = new();
             protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}
 
             internal sealed class Cached0 : CommandFactory1
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }
             internal sealed class Cached1 : CommandFactory1
             {
                 protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;
+                [global::System.ThreadStatic] // note this works correctly with ref-return
                 private static global::System.Data.Common.DbCommand? s_Storage;
 
             }

Original file line number	Diff line number	Diff line change
`@@ -579,30 +579,34 @@ private static void WriteCommandFactory(in GenerateState ctx, string baseFactory`
`579`	`579`	`if (additionalCommandState is not null && additionalCommandState.HasCommandProperties)`
`580`	`580`	`{`
`581`	`581`	`sb.Indent()`
`582`		`- .NewLine().Append("var cmd = TryReuse(ref Storage, sql, commandType, args);")`
	`582`	`+ .NewLine().Append("var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);")`
`583`	`583`	`.NewLine().Append("if (cmd is null)").Indent()`
`584`	`584`	`.NewLine().Append("cmd = base.GetCommand(connection, sql, commandType, args);");`
`585`	`585`	`WriteCommandProperties(ctx, sb, "cmd", additionalCommandState.CommandProperties);`
`586`	`586`	`sb.Outdent().NewLine().Append("return cmd;").Outdent();`
`587`	`587`	`}`
`588`	`588`	`else`
`589`	`589`	`{`
`590`		`- sb.Indent(false).NewLine().Append(" => TryReuse(ref Storage, sql, commandType, args) ?? base.GetCommand(connection, sql, commandType, args);").Outdent(false);`
	`590`	`+ sb.Indent(false).NewLine().Append(" => TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool) ?? base.GetCommand(connection, sql, commandType, args);").Outdent(false);`
`591`	`591`	`}`
`592`		`- sb.NewLine().NewLine().Append("public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);").NewLine();`
	`592`	`+ sb.NewLine().NewLine().Append("public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);").NewLine();`
`593`	`593`
`594`	`594`	`if (cacheCount == 1)`
`595`	`595`	`{`
	`596`	`+ sb.Append("private static readonly DbCommandCache _cmdPool = new();").NewLine();`
	`597`	`+ sb.Append("[global::System.ThreadStatic] // note this works correctly with ref").NewLine();`
`596`	`598`	`sb.Append("private static global::System.Data.Common.DbCommand? Storage;").NewLine();`
`597`	`599`	`}`
`598`	`600`	`else`
`599`	`601`	`{`
	`602`	`+ sb.Append("private readonly DbCommandCache _cmdPool = new(); // note: per cache instance").NewLine();`
`600`	`603`	`sb.Append("protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}").NewLine().NewLine();`
`601`	`604`
`602`	`605`	`for (int i = 0; i < cacheCount; i++)`
`603`	`606`	`{`
`604`	`607`	`sb.Append("internal sealed class Cached").Append(i).Append(" : CommandFactory").Append(index).Indent().NewLine()`
`605`	`608`	`.Append("protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;").NewLine()`
	`609`	`+ .Append("[global::System.ThreadStatic] // note this works correctly with ref-return").NewLine()`
`606`	`610`	`.Append("private static global::System.Data.Common.DbCommand? s_Storage;").NewLine()`
`607`	`611`	`.Outdent().NewLine();`
`608`	`612`	`}`
Original file line number	Diff line number	Diff line change
`@@ -199,7 +199,7 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje`
`199`	`199`	`public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,`
`200`	`200`	`string sql, global::System.Data.CommandType commandType, object? args)`
`201`	`201`	`{`
`202`		`- var cmd = TryReuse(ref Storage, sql, commandType, args);`
	`202`	`+ var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);`
`203`	`203`	`if (cmd is null)`
`204`	`204`	`{`
`205`	`205`	`cmd = base.GetCommand(connection, sql, commandType, args);`
`@@ -212,7 +212,9 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje`
`212`	`212`	`return cmd;`
`213`	`213`	`}`
`214`	`214`
`215`		`- public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);`
	`215`	`+ public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);`
	`216`	`+ private readonly DbCommandCache _cmdPool = new();`
	`217`	`+ [global::System.ThreadStatic] // note this works correctly with ref`
`216`	`218`	`private static global::System.Data.Common.DbCommand? Storage;`
`217`	`219`
`218`	`220`	`}`
`@@ -256,7 +258,7 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje`
`256`	`258`	`public override global::System.Data.Common.DbCommand GetCommand(global::System.Data.Common.DbConnection connection,`
`257`	`259`	`string sql, global::System.Data.CommandType commandType, object? args)`
`258`	`260`	`{`
`259`		`- var cmd = TryReuse(ref Storage, sql, commandType, args);`
	`261`	`+ var cmd = TryReuseThreadStatic(ref Storage, sql, commandType, args, _cmdPool);`
`260`	`262`	`if (cmd is null)`
`261`	`263`	`{`
`262`	`264`	`cmd = base.GetCommand(connection, sql, commandType, args);`
`@@ -269,18 +271,21 @@ public override void UpdateParameters(in global::Dapper.UnifiedCommand cmd, obje`
`269`	`271`	`return cmd;`
`270`	`272`	`}`
`271`	`273`
`272`		`- public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycle(ref Storage, command);`
	`274`	`+ public override bool TryRecycle(global::System.Data.Common.DbCommand command) => TryRecycleThreadStatic(ref Storage, command, _cmdPool);`
	`275`	`+ private readonly DbCommandCache _cmdPool = new();`
`273`	`276`	`protected abstract ref global::System.Data.Common.DbCommand? Storage {get;}`
`274`	`277`
`275`	`278`	`internal sealed class Cached0 : CommandFactory1`
`276`	`279`	`{`
`277`	`280`	`protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;`
	`281`	`+ [global::System.ThreadStatic] // note this works correctly with ref-return`
`278`	`282`	`private static global::System.Data.Common.DbCommand? s_Storage;`
`279`	`283`
`280`	`284`	`}`
`281`	`285`	`internal sealed class Cached1 : CommandFactory1`
`282`	`286`	`{`
`283`	`287`	`protected override ref global::System.Data.Common.DbCommand? Storage => ref s_Storage;`
	`288`	`+ [global::System.ThreadStatic] // note this works correctly with ref-return`
`284`	`289`	`private static global::System.Data.Common.DbCommand? s_Storage;`
`285`	`290`
`286`	`291`	`}`