优化first代码

Author: xuejmnet

src/ShardingCore/Core/Internal/FixedElementCollection.cs

@@ -18,13 +18,15 @@ public FixedElementCollection(int capacity)
         public int VirtualElementCount => _virtualElementCount;
         public int ReallyElementCount => _list.Count;
 
-        public void Add(TEntity element)
+        public bool Add(TEntity element)
         {
             _virtualElementCount++;
             if (VirtualElementCount <= _capacity)
             {
                 _list.Add(element);
+                return true;
             }
+            return false;
         }
 
         public TEntity FirstOrDefault()

src/ShardingCore/Extensions/StreamMergeEnumerableExtension.cs

@@ -26,32 +26,44 @@ public static List<TEntity> ToStreamList<TEntity>(this IEnumerable<TEntity> sour
         {
             return source.ToList();
         }
-        public static FixedElementCollection<TEntity> ToFixedElementStreamList<TEntity>(this IEnumerable<TEntity> source,int capacity)
+        public static FixedElementCollection<TEntity> ToFixedElementStreamList<TEntity>(this IEnumerable<TEntity> source,int capacity,int maxVirtualElementCount)
         {
             var fixedElementCollection = new FixedElementCollection<TEntity>(capacity);
-            var enumerator = source.GetEnumerator();
+            using var enumerator = source.GetEnumerator();
             while (enumerator.MoveNext())
             {
                 fixedElementCollection.Add(enumerator.Current);
+                if (fixedElementCollection.VirtualElementCount >= maxVirtualElementCount)
+                {
+                    break;
+                }
             }
             return fixedElementCollection;
         }
 
 
-        public static async Task<FixedElementCollection<TEntity>> ToFixedElementStreamListAsync<TEntity>(this IAsyncEnumerable<TEntity> source,int capacity,CancellationToken cancellationToken=default)
+        public static async Task<FixedElementCollection<TEntity>> ToFixedElementStreamListAsync<TEntity>(this IAsyncEnumerable<TEntity> source,int capacity,int maxVirtualElementCount,CancellationToken cancellationToken=default)
         {
             var fixedElementCollection = new FixedElementCollection<TEntity>(capacity);
 #if EFCORE2
             var asyncEnumerator = source.GetEnumerator();
             while (await asyncEnumerator.MoveNext(cancellationToken))
             {
                 fixedElementCollection.Add(asyncEnumerator.Current);
+                if (fixedElementCollection.VirtualElementCount >= maxVirtualElementCount)
+                {
+                    break;
+                }
             }
 #endif
 #if !EFCORE2
             await foreach (var element in source.WithCancellation(cancellationToken))
             {
                 fixedElementCollection.Add(element);
+                if (fixedElementCollection.VirtualElementCount >= maxVirtualElementCount)
+                {
+                    break;
+                }
             }
 #endif
             return fixedElementCollection;

src/ShardingCore/Sharding/Enumerators/StreamMergeAsync/OneAtMostElementStreamMergeAsyncEnumerator.cs

@@ -8,86 +8,72 @@ namespace ShardingCore.Sharding.Enumerators.StreamMergeAsync
 {
     internal class OneAtMostElementStreamMergeAsyncEnumerator<T> : IStreamMergeAsyncEnumerator<T>
     {
-        private List<T>.Enumerator _enumerator;
-        private bool skip;
+        private int _moveIndex = 0;
+        private T _constantElement;
 
         public OneAtMostElementStreamMergeAsyncEnumerator(IStreamMergeAsyncEnumerator<T> streamMergeAsyncEnumerator)
         {
-            var list = new List<T>();
-            if (streamMergeAsyncEnumerator.HasElement())
+            _constantElement=streamMergeAsyncEnumerator.ReallyCurrent;
+        }
+
+
+        private bool MoveNext0()
+        {
+            if (_moveIndex >= 1)
             {
-                list.Add(streamMergeAsyncEnumerator.ReallyCurrent);
+                return false;
             }
 
-            _enumerator = list.GetEnumerator();
-            _enumerator.MoveNext();
-            skip = true;
+            _moveIndex++;
+            return HasElement();
         }
-
 #if !EFCORE2&&!EFCORE3&&!EFCORE5
         public  ValueTask DisposeAsync()
         {
-            _enumerator.Dispose();
             return ValueTask.CompletedTask;
         }
-
         public  ValueTask<bool> MoveNextAsync()
         {
-            var moveNext = _enumerator.MoveNext();
+            var moveNext = MoveNext0();
             return ValueTask.FromResult<bool>(moveNext);
         }
 
         public void Dispose()
         {
-            _enumerator.Dispose();
         }
 
 #endif
 #if EFCORE3 || EFCORE5
         public  ValueTask DisposeAsync()
         {
-            _enumerator.Dispose();
             return new ValueTask();
         }
 
         public  ValueTask<bool> MoveNextAsync()
         {
-            var moveNext = _enumerator.MoveNext();
+            var moveNext = MoveNext0();
             return new ValueTask<bool>(moveNext);
         }
 
         public void Dispose()
         {
-            _enumerator.Dispose();
         }
 
 #endif
         public bool MoveNext()
         {
-            if (skip)
-            {
-                skip = false;
-                return null != _enumerator.Current;
-            }
-
-            var moveNext = _enumerator.MoveNext();
+            var moveNext = MoveNext0();
             return moveNext;
         }
 
         public bool SkipFirst()
         {
-            if (skip)
-            {
-                skip = false;
-                return true;
-            }
-
             return false;
         }
 
         public bool HasElement()
         {
-            return null != _enumerator.Current;
+            return null != _constantElement;
         }
 
 
@@ -102,29 +88,23 @@ public void Reset()
 
         public T GetCurrent()
         {
-            if (skip)
+            if (_moveIndex==0)
                 return default;
-            return _enumerator.Current;
+            return _constantElement;
         }
 
         public T GetReallyCurrent()
         {
-            return _enumerator.Current;
+            return _constantElement;
         }
 #if EFCORE2
         public void Dispose()
         {
-            _enumerator.Dispose();
         }
 
         public  Task<bool> MoveNext(CancellationToken cancellationToken = new CancellationToken())
         {
-            if (skip)
-            {
-                skip = false;
-               return Task.FromResult(null != _enumerator.Current);
-            }
-            var moveNext = _enumerator.MoveNext();
+            var moveNext = MoveNext0();
             return Task.FromResult(moveNext);
         }
 

src/ShardingCore/Sharding/MergeEngines/Executors/Abstractions/AbstractExecutor.cs

@@ -90,7 +90,7 @@ private async Task<LinkedList<TResult>> ExecuteAsync0(bool async,
                 if (dataSourceSqlExecutorUnit.ConnectionMode == ConnectionModeEnum.CONNECTION_STRICTLY)
                 {
                     MergeParallelExecuteResult(result, routeQueryResults.Select(o => o.MergeResult), async);
-                    var dbContexts = routeQueryResults.Select(o => o.DbContext);
+                    var dbContexts = routeQueryResults.Where(o=>o!=null).Select(o => o.DbContext).ToArray();
                     foreach (var dbContext in dbContexts)
                     {
                         await streamMergeContext.DbContextDisposeAsync(dbContext);