Query: Add RowNumberExpression support to convert lateral joins to joins

This enables support for non-scalar single result on Sqlite. Resolves #10001 for Sqlite Resolves #17292
dotnet · Aug 21, 2019 · 8e98077 · 8e98077
1 parent a04f5a3
commit 8e98077
Show file tree

Hide file tree

Showing 10 changed files with 273 additions and 107 deletions.
diff --git a/src/EFCore.Relational/Query/QuerySqlGenerator.cs b/src/EFCore.Relational/Query/QuerySqlGenerator.cs
@@ -762,5 +762,22 @@ protected override Expression VisitSubSelect(ScalarSubqueryExpression scalarSubq
 
             return scalarSubqueryExpression;
         }
+
+        protected override Expression VisitRowNumber(RowNumberExpression rowNumberExpression)
+        {
+            _relationalCommandBuilder.Append("ROW_NUMBER() OVER(");
+            if (rowNumberExpression.Partitions.Any())
+            {
+                _relationalCommandBuilder.Append("PARTITION BY ");
+                GenerateList(rowNumberExpression.Partitions, e => Visit(e));
+                _relationalCommandBuilder.Append(" ");
+            }
+
+            _relationalCommandBuilder.Append("ORDER BY ");
+            GenerateList(rowNumberExpression.Orderings, e => Visit(e));
+            _relationalCommandBuilder.Append(")");
+
+            return rowNumberExpression;
+        }
     }
 }
diff --git a/src/EFCore.Relational/Query/SqlExpressionVisitor.cs b/src/EFCore.Relational/Query/SqlExpressionVisitor.cs
@@ -3,7 +3,6 @@
 
 using System.Linq.Expressions;
 using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
-using Microsoft.EntityFrameworkCore.Utilities;
 
 namespace Microsoft.EntityFrameworkCore.Query
 {
@@ -52,6 +51,9 @@ protected override Expression VisitExtension(Expression extensionExpression)
                 case ProjectionExpression projectionExpression:
                     return VisitProjection(projectionExpression);
 
+                case RowNumberExpression rowNumberExpression:
+                    return VisitRowNumber(rowNumberExpression);
+
                 case SelectExpression selectExpression:
                     return VisitSelect(selectExpression);
 
@@ -83,6 +85,7 @@ protected override Expression VisitExtension(Expression extensionExpression)
             return base.VisitExtension(extensionExpression);
         }
 
+        protected abstract Expression VisitRowNumber(RowNumberExpression rowNumberExpression);
         protected abstract Expression VisitExists(ExistsExpression existsExpression);
         protected abstract Expression VisitIn(InExpression inExpression);
         protected abstract Expression VisitCrossJoin(CrossJoinExpression crossJoinExpression);

diff --git a/src/EFCore.Relational/Query/SqlExpressions/CaseExpression.cs b/src/EFCore.Relational/Query/SqlExpressions/CaseExpression.cs
@@ -122,6 +122,7 @@ private bool Equals(CaseExpression caseExpression)
         public override int GetHashCode()
         {
             var hash = new HashCode();
+            hash.Add(base.GetHashCode());
             hash.Add(Operand);
             for (var i = 0; i < WhenClauses.Count; i++)
             {

diff --git a/src/EFCore.Relational/Query/SqlExpressions/RowNumberExpression.cs b/src/EFCore.Relational/Query/SqlExpressions/RowNumberExpression.cs
@@ -0,0 +1,96 @@
+// 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.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using Microsoft.EntityFrameworkCore.Storage;
+using Microsoft.EntityFrameworkCore.Utilities;
+
+namespace Microsoft.EntityFrameworkCore.Query.SqlExpressions
+{
+    public class RowNumberExpression : SqlExpression
+    {
+        public RowNumberExpression(IReadOnlyList<SqlExpression> partitions, IReadOnlyList<OrderingExpression> orderings, RelationalTypeMapping typeMapping)
+            : base(typeof(long), typeMapping)
+        {
+            Check.NotEmpty(orderings, nameof(orderings));
+
+            Partitions = partitions;
+            Orderings = orderings;
+        }
+
+        public virtual IReadOnlyList<SqlExpression> Partitions { get; }
+        public virtual IReadOnlyList<OrderingExpression> Orderings { get; }
+
+        protected override Expression VisitChildren(ExpressionVisitor visitor)
+        {
+            var changed = false;
+            var partitions = new List<SqlExpression>();
+            foreach (var partition in Partitions)
+            {
+                var newPartition = (SqlExpression)visitor.Visit(partition);
+                changed |= newPartition != partition;
+                partitions.Add(newPartition);
+            }
+
+            var orderings = new List<OrderingExpression>();
+            foreach (var ordering in Orderings)
+            {
+                var newOrdering = (OrderingExpression)visitor.Visit(ordering);
+                changed |= newOrdering != ordering;
+                orderings.Add(newOrdering);
+            }
+
+            return changed
+                ? new RowNumberExpression(partitions, orderings, TypeMapping)
+                : this;
+        }
+
+        public virtual RowNumberExpression Update(IReadOnlyList<SqlExpression> partitions, IReadOnlyList<OrderingExpression> orderings)
+        {
+            return (Partitions == null ? partitions == null : Partitions.SequenceEqual(partitions))
+                    && Orderings.SequenceEqual(orderings)
+                ? this
+                : new RowNumberExpression(partitions, orderings, TypeMapping);
+        }
+
+        public override void Print(ExpressionPrinter expressionPrinter)
+        {
+            expressionPrinter.Append("ROW_NUMBER() OVER(PARTITION BY ");
+            expressionPrinter.VisitList(Partitions);
+            expressionPrinter.Append(" ORDER BY ");
+            expressionPrinter.VisitList(Orderings);
+            expressionPrinter.Append(")");
+        }
+
+        public override bool Equals(object obj)
+            => obj != null
+            && (ReferenceEquals(this, obj)
+                || obj is RowNumberExpression rowNumberExpression
+                    && Equals(rowNumberExpression));
+
+        private bool Equals(RowNumberExpression rowNumberExpression)
+            => base.Equals(rowNumberExpression)
+            && (Partitions == null ? rowNumberExpression.Partitions == null : Partitions.SequenceEqual(rowNumberExpression.Partitions))
+            && Orderings.SequenceEqual(rowNumberExpression.Orderings);
+
+        public override int GetHashCode()
+        {
+            var hash = new HashCode();
+            hash.Add(base.GetHashCode());
+            foreach (var partition in Partitions)
+            {
+                hash.Add(partition);
+            }
+
+            foreach (var ordering in Orderings)
+            {
+                hash.Add(ordering);
+            }
+
+            return hash.ToHashCode();
+        }
+    }
+}
diff --git a/src/EFCore.Relational/Query/SqlExpressions/SelectExpression.cs b/src/EFCore.Relational/Query/SqlExpressions/SelectExpression.cs
@@ -559,9 +559,9 @@ ColumnExpression addSetOperationColumnProjections(
             }
         }
 
-        private ColumnExpression GenerateOuterColumn(SqlExpression projection)
+        private ColumnExpression GenerateOuterColumn(SqlExpression projection, string alias = null)
         {
-            var index = AddToProjection(projection);
+            var index = AddToProjection(projection, alias);
             return new ColumnExpression(_projection[index], this);
         }
 
@@ -1009,6 +1009,22 @@ public override Expression Visit(Expression expression)
             }
         }
 
+        private void GetPartitions(SqlExpression sqlExpression, List<SqlExpression> partitions)
+        {
+            if (sqlExpression is SqlBinaryExpression sqlBinaryExpression)
+            {
+                if (sqlBinaryExpression.OperatorType == ExpressionType.Equal)
+                {
+                    partitions.Add(sqlBinaryExpression.Right);
+                }
+                else if (sqlBinaryExpression.OperatorType == ExpressionType.AndAlso)
+                {
+                    GetPartitions(sqlBinaryExpression.Left, partitions);
+                    GetPartitions(sqlBinaryExpression.Right, partitions);
+                }
+            }
+        }
+
         private enum JoinType
         {
             InnerJoin,
@@ -1027,6 +1043,10 @@ private void AddJoin(
             // Try to convert lateral join to normal join
             if (joinType == JoinType.InnerJoinLateral || joinType == JoinType.LeftJoinLateral)
             {
+                // Doing for limit only since limit + offset may need sum
+                var limit = innerSelectExpression.Limit;
+                innerSelectExpression.Limit = null;
+
                 joinPredicate = TryExtractJoinKey(innerSelectExpression);
                 if (joinPredicate != null)
                 {
@@ -1035,14 +1055,42 @@ private void AddJoin(
                     if (containsOuterReference)
                     {
                         innerSelectExpression.ApplyPredicate(joinPredicate);
+                        innerSelectExpression.ApplyLimit(limit);
                     }
                     else
                     {
+                        if (limit != null)
+                        {
+                            var partitions = new List<SqlExpression>();
+                            GetPartitions(joinPredicate, partitions);
+                            var orderings = innerSelectExpression.Orderings.Any()
+                                ? innerSelectExpression.Orderings
+                                : innerSelectExpression._identifier.Select(e => new OrderingExpression(e, true));
+                            var rowNumberExpression = new RowNumberExpression(partitions, orderings.ToList(), limit.TypeMapping);
+                            innerSelectExpression.ClearOrdering();
+
+                            var projectionMappings = innerSelectExpression.PushdownIntoSubquery();
+                            var subquery = (SelectExpression)innerSelectExpression.Tables[0];
+
+                            joinPredicate = new SqlRemappingVisitor(
+                                projectionMappings, subquery)
+                                .Remap(joinPredicate);
+
+                            var outerColumn = subquery.GenerateOuterColumn(rowNumberExpression, "row");
+                            var predicate = new SqlBinaryExpression(
+                                ExpressionType.LessThanOrEqual, outerColumn, limit, typeof(bool), joinPredicate.TypeMapping);
+                            innerSelectExpression.ApplyPredicate(predicate);
+                        }
+
                         AddJoin(joinType == JoinType.InnerJoinLateral ? JoinType.InnerJoin : JoinType.LeftJoin,
                             innerSelectExpression, transparentIdentifierType, joinPredicate);
                         return;
                     }
                 }
+                else
+                {
+                    innerSelectExpression.ApplyLimit(limit);
+                }
             }
 
             // Verify what are the cases of pushdown for inner & outer both sides

diff --git a/src/EFCore.SqlServer/Query/Internal/SearchConditionConvertingExpressionVisitor.cs b/src/EFCore.SqlServer/Query/Internal/SearchConditionConvertingExpressionVisitor.cs
@@ -361,5 +361,31 @@ protected override Expression VisitSubSelect(ScalarSubqueryExpression scalarSubq
 
             return ApplyConversion(scalarSubqueryExpression.Update(subquery), condition: false);
         }
+
+        protected override Expression VisitRowNumber(RowNumberExpression rowNumberExpression)
+        {
+            var parentSearchCondition = _isSearchCondition;
+            _isSearchCondition = false;
+            var changed = false;
+            var partitions = new List<SqlExpression>();
+            foreach (var partition in rowNumberExpression.Partitions)
+            {
+                var newPartition = (SqlExpression)Visit(partition);
+                changed |= newPartition != partition;
+                partitions.Add(newPartition);
+            }
+
+            var orderings = new List<OrderingExpression>();
+            foreach (var ordering in rowNumberExpression.Orderings)
+            {
+                var newOrdering = (OrderingExpression)Visit(ordering);
+                changed |= newOrdering != ordering;
+                orderings.Add(newOrdering);
+            }
+
+            _isSearchCondition = parentSearchCondition;
+
+            return ApplyConversion(rowNumberExpression.Update(partitions, orderings), condition: false);
+        }
     }
 }