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Query: Optimize certain types of GroupJoin/SelectMany queries
In some circumstances, a GroupJoin/SelectMany pattern (with or without DefaultIfEmpty) can be optimized by shifting body clauses from the AdditionalFromClause into the GroupJoinClause. These changes implement that optimization.
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99 changes: 99 additions & 0 deletions
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...Core/Query/ExpressionVisitors/Internal/AdditionalFromClauseOptimizingQueryModelVisitor.cs
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| @@ -0,0 +1,99 @@ | ||
| // Copyright (c) .NET Foundation. All rights reserved. | ||
| // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information. | ||
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| using System.Linq; | ||
| using System.Linq.Expressions; | ||
| using JetBrains.Annotations; | ||
| using Microsoft.EntityFrameworkCore.Query.Internal; | ||
| using Remotion.Linq; | ||
| using Remotion.Linq.Clauses; | ||
| using Remotion.Linq.Clauses.Expressions; | ||
| using Remotion.Linq.Clauses.ExpressionVisitors; | ||
| using Remotion.Linq.Clauses.ResultOperators; | ||
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| namespace Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal | ||
| { | ||
| /// <summary> | ||
| /// This API supports the Entity Framework Core infrastructure and is not intended to be used | ||
| /// directly from your code. This API may change or be removed in future releases. | ||
| /// </summary> | ||
| public class AdditionalFromClauseOptimizingQueryModelVisitor : QueryModelVisitorBase | ||
| { | ||
| /// <summary> | ||
| /// This API supports the Entity Framework Core infrastructure and is not intended to be used | ||
| /// directly from your code. This API may change or be removed in future releases. | ||
| /// </summary> | ||
| public override void VisitQueryModel([NotNull] QueryModel queryModel) | ||
| { | ||
| queryModel.TransformExpressions(new TransformingQueryModelExpressionVisitor<AdditionalFromClauseOptimizingQueryModelVisitor>(this).Visit); | ||
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|
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| base.VisitQueryModel(queryModel); | ||
| } | ||
|
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| /// <summary> | ||
| /// This API supports the Entity Framework Core infrastructure and is not intended to be used | ||
| /// directly from your code. This API may change or be removed in future releases. | ||
| /// </summary> | ||
| public override void VisitAdditionalFromClause( | ||
| [NotNull] AdditionalFromClause fromClause, | ||
| [NotNull] QueryModel queryModel, | ||
| int index) | ||
| { | ||
| if (fromClause.FromExpression is SubQueryExpression subQueryExpression | ||
| && subQueryExpression.QueryModel.MainFromClause.FromExpression is QuerySourceReferenceExpression qsre | ||
| && subQueryExpression.QueryModel.SelectClause.Selector is QuerySourceReferenceExpression | ||
| && qsre.ReferencedQuerySource is GroupJoinClause groupJoinClause | ||
| && queryModel.CountQuerySourceReferences(groupJoinClause) == 1 | ||
| && subQueryExpression.QueryModel.BodyClauses.Any() | ||
| && subQueryExpression.QueryModel.BodyClauses.All(c => c is WhereClause)) | ||
| { | ||
| if (groupJoinClause.JoinClause.InnerSequence is SubQueryExpression innerSequenceSubQuery) | ||
| { | ||
| if (!innerSequenceSubQuery.QueryModel.ResultOperators.Any(r => r is TakeResultOperator || r is SkipResultOperator)) | ||
| { | ||
| ShiftWhereClauses(subQueryExpression.QueryModel, innerSequenceSubQuery.QueryModel); | ||
| } | ||
| } | ||
| else | ||
| { | ||
| var newMainFromClause = new MainFromClause( | ||
| groupJoinClause.JoinClause.ItemName, | ||
| groupJoinClause.JoinClause.ItemType, | ||
| groupJoinClause.JoinClause.InnerSequence); | ||
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| var newSelectClause = new SelectClause( | ||
| new QuerySourceReferenceExpression(newMainFromClause)); | ||
|
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| var newSubQueryModel = new QueryModel(newMainFromClause, newSelectClause); | ||
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| ShiftWhereClauses(subQueryExpression.QueryModel, newSubQueryModel); | ||
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| var newSubQueryExpression = new SubQueryExpression(newSubQueryModel); | ||
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| groupJoinClause.JoinClause.InnerSequence = newSubQueryExpression; | ||
| } | ||
| } | ||
| } | ||
|
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| private void ShiftWhereClauses(QueryModel oldQueryModel, QueryModel newQueryModel) | ||
| { | ||
| var querySourceMapping = new QuerySourceMapping(); | ||
|
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| querySourceMapping.AddMapping( | ||
| oldQueryModel.MainFromClause, | ||
| new QuerySourceReferenceExpression(newQueryModel.MainFromClause)); | ||
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| foreach (var whereClause in oldQueryModel.BodyClauses.Cast<WhereClause>().ToArray()) | ||
| { | ||
| whereClause.Predicate | ||
| = ReferenceReplacingExpressionVisitor.ReplaceClauseReferences( | ||
| whereClause.Predicate, | ||
| querySourceMapping, | ||
| throwOnUnmappedReferences: false); | ||
|
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| oldQueryModel.BodyClauses.Remove(whereClause); | ||
| newQueryModel.BodyClauses.Add(whereClause); | ||
| } | ||
| } | ||
| } | ||
| } |
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