Add implicit ORDER BY Distance for VectorSearch translation

src/EFCore.Relational/Query/SqlExpressions/SelectExpression.cs

@@ -2029,6 +2029,18 @@ public void SetLimit(SqlExpression sqlExpression)
         }
     }
 
+    /// <summary>
+    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+    ///     any release. You should only use it directly in your code with extreme caution and knowing that
+    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+    /// </summary>
+    [EntityFrameworkInternal]
+    public void SetOffset(SqlExpression? sqlExpression)
+    {
+        Offset = sqlExpression;
+    }
+
     /// <summary>
     ///     Applies offset to the <see cref="SelectExpression" /> to skip the number of rows in the result set.
     /// </summary>

src/EFCore.SqlServer/Extensions/SqlServerQueryableExtensions.cs

@@ -30,8 +30,8 @@ public static class SqlServerQueryableExtensions
     /// </param>
     /// <remarks>
     ///     <para>
-    ///         Compose the returned query with <c>OrderBy(r => r.Distance)</c> and <c>Take(...)</c> to limit the results as required
-    ///         for approximate vector search.
+    ///         Results are implicitly ordered by distance ascending. Compose the returned query with <c>Take(...)</c> to limit the
+    ///         number of results as required for approximate vector search.
     ///     </para>
     /// </remarks>
     /// <seealso href="https://learn.microsoft.com/sql/t-sql/functions/vector-search-transact-sql">

src/EFCore.SqlServer/Query/Internal/SqlServerQueryableMethodTranslatingExpressionVisitor.cs

@@ -147,12 +147,18 @@ var metric
                     var valueProjectionMember = new ProjectionMember().Append(resultType.GetProperty(nameof(VectorSearchResult<>.Value))!);
                     var distanceProjectionMember = new ProjectionMember().Append(resultType.GetProperty(nameof(VectorSearchResult<>.Distance))!);
 
+                    var distanceColumn = new ColumnExpression("Distance", vectorSearchFunction.Alias, typeof(double), _typeMappingSource.FindMapping(typeof(double)), nullable: false);
+
                     select.ReplaceProjection(new Dictionary<ProjectionMember, Expression>
                     {
                         [valueProjectionMember] = entityProjection,
-                        [distanceProjectionMember] = new ColumnExpression("Distance", vectorSearchFunction.Alias, typeof(double), _typeMappingSource.FindMapping(typeof(double)), nullable: false)
+                        [distanceProjectionMember] = distanceColumn
                     });
 
+                    // VECTOR_SEARCH() results are implicitly ordered by distance ascending; add this ordering so that
+                    // users can compose with Take() without needing an explicit OrderBy(r => r.Distance).
+                    select.AppendOrdering(new OrderingExpression(distanceColumn, ascending: true));
+
                     var shaper = Expression.New(
                         resultType.GetConstructors().Single(),
                         arguments:
@@ -795,29 +801,92 @@ bool TryTranslate(
         }
     }
 
+    /// <summary>
+    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+    ///     any release. You should only use it directly in your code with extreme caution and knowing that
+    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+    /// </summary>
+    protected override ShapedQueryExpression? TranslateTake(ShapedQueryExpression source, Expression count)
+    {
+        var selectExpression = (SelectExpression)source.QueryExpression;
+
+        // When VECTOR_SEARCH() is present and an Offset has already been applied (i.e. Skip().Take()), we need to ensure that the
+        // generated SQL uses TOP WITH APPROXIMATE in a subquery, rather than the default OFFSET...FETCH which doesn't use the
+        // vector index. We push down a subquery with TOP(Skip + Take) WITH APPROXIMATE, and apply OFFSET...FETCH on the outer query.
+        if (selectExpression is { Offset: { } existingOffset }
+            && selectExpression.Tables.Any(t => t.UnwrapJoin() is TableValuedFunctionExpression { Name: "VECTOR_SEARCH" }))
+        {
+            var translation = TranslateExpression(count);
+            if (translation == null)
+            {
+                return null;
+            }
+
+            var combinedLimit = _sqlExpressionFactory.Add(existingOffset, translation);
+
+#pragma warning disable EF1001 // Internal EF Core API usage.
+            // Clear the offset so the inner subquery uses TOP(M+N) instead of OFFSET...FETCH
+            selectExpression.SetOffset(null);
+            selectExpression.SetLimit(combinedLimit);
+
+            // Push down: inner gets TOP(Skip+Take) WITH APPROXIMATE, outer is clean
+            selectExpression.PushdownIntoSubquery();
+
+            // Apply the original offset and take on the outer query as OFFSET...FETCH
+            selectExpression.ApplyOffset(existingOffset);
+            selectExpression.SetLimit(translation);
+#pragma warning restore EF1001 // Internal EF Core API usage.
+
+            return source;
+        }
+
+        return base.TranslateTake(source, count);
+    }
+
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
     ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
     ///     any release. You should only use it directly in your code with extreme caution and knowing that
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     protected override bool IsNaturallyOrdered(SelectExpression selectExpression)
-        => selectExpression is
+        => selectExpression switch
         {
-            Tables: [SqlServerOpenJsonExpression openJsonExpression, ..],
-            Orderings:
-                [
-                {
-                    Expression: SqlUnaryExpression
+            // OPENJSON rows are naturally ordered by their "key" column (array index), ascending.
+            // EF adds this ordering implicitly when expanding JSON arrays; treat it as natural to avoid spurious
+            // "Distinct after OrderBy without row limiting operator" warnings.
+            {
+                Tables: [SqlServerOpenJsonExpression openJsonExpression, ..],
+                Orderings:
+                    [
                     {
-                        OperatorType: ExpressionType.Convert,
-                        Operand: ColumnExpression { Name: "key", TableAlias: var orderingTableAlias }
-                    },
-                    IsAscending: true
-                }
-                ]
-        }
-            && orderingTableAlias == openJsonExpression.Alias;
+                        Expression: SqlUnaryExpression
+                        {
+                            OperatorType: ExpressionType.Convert,
+                            Operand: ColumnExpression { Name: "key", TableAlias: var openJsonOrderingTableAlias }
+                        },
+                        IsAscending: true
+                    }
+                    ]
+            } when openJsonOrderingTableAlias == openJsonExpression.Alias => true,
+
+            // VECTOR_SEARCH() results are naturally ordered by Distance ascending.
+            // EF adds this ordering implicitly during VectorSearch translation; treat it as natural to avoid spurious
+            // "Distinct after OrderBy without row limiting operator" warnings.
+            {
+                Tables: [TableValuedFunctionExpression { Name: "VECTOR_SEARCH" } vectorSearchFunction, ..],
+                Orderings:
+                    [
+                    {
+                        Expression: ColumnExpression { Name: "Distance", TableAlias: var vectorSearchOrderingTableAlias },
+                        IsAscending: true
+                    }
+                    ]
+            } when vectorSearchOrderingTableAlias == vectorSearchFunction.Alias => true,
+
+            _ => false
+        };
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to

test/EFCore.SqlServer.FunctionalTests/Query/Translations/VectorTranslationsSqlServerTest.cs

@@ -77,7 +77,6 @@ public async Task VectorSearch_project_entity_and_distance()
 
         var results = await ctx.VectorEntities
             .VectorSearch(e => e.Vector, similarTo: vector, "cosine")
-            .OrderBy(e => e.Distance)
             .Take(1)
             .ToListAsync();
 
@@ -103,7 +102,7 @@ ORDER BY [v0].[Distance]
     [ConditionalFact]
     [SqlServerCondition(SqlServerCondition.IsAzureSql)]
     [Experimental("EF9105")]
-    public async Task VectorSearch_project_entity_only_with_distance_filter_and_ordering()
+    public async Task VectorSearch_project_entity_only_with_distance_filter()
     {
         using var ctx = CreateContext();
 
@@ -112,7 +111,6 @@ public async Task VectorSearch_project_entity_only_with_distance_filter_and_orde
         var results = await ctx.VectorEntities
             .VectorSearch(e => e.Vector, similarTo: vector, "cosine")
             .Where(e => e.Distance < 0.01)
-            .OrderBy(e => e.Distance)
             .Select(e => e.Value)
             .Take(3)
             .ToListAsync();
@@ -151,7 +149,6 @@ public async Task VectorSearch_in_subquery()
 
         var results = await ctx.VectorEntities
             .VectorSearch(e => e.Vector, similarTo: vector, "cosine")
-            .OrderBy(e => e.Distance)
             .Take(3)
             .Select(e => new { e.Value.Id, e.Distance })
             .Where(e => e.Distance < 0.01)
@@ -183,6 +180,86 @@ ORDER BY [v1].[Distance]
 """);
     }
 
+    // The latest vector index version (required for VECTOR_SEARCH) is only available on Azure SQL (#36384).
+    [ConditionalFact]
+    [SqlServerCondition(SqlServerCondition.IsAzureSql)]
+    [Experimental("EF9105")]
+    public async Task VectorSearch_with_Skip_and_Take()
+    {
+        using var ctx = CreateContext();
+
+        var vector = new SqlVector<float>(new float[] { 1, 2, 100 });
+
+        var results = await ctx.VectorEntities
+            .VectorSearch(e => e.Vector, similarTo: vector, "cosine")
+            .Skip(1)
+            .Take(2)
+            .ToListAsync();
+
+        Assert.Equal(2, results.Count);
+
+        AssertSql(
+            """
+@p1='1'
+@p2='2'
+@p='Microsoft.Data.SqlTypes.SqlVector`1[System.Single]' (Size = 20) (DbType = Binary)
+
+SELECT [v1].[Id], [v1].[Distance]
+FROM (
+    SELECT TOP(@p1 + @p2) WITH APPROXIMATE [v].[Id], [v0].[Distance]
+    FROM VECTOR_SEARCH(
+        TABLE = [VectorEntities] AS [v],
+        COLUMN = [Vector],
+        SIMILAR_TO = @p,
+        METRIC = 'cosine'
+    ) AS [v0]
+    ORDER BY [v0].[Distance]
+) AS [v1]
+ORDER BY [v1].[Distance]
+OFFSET @p1 ROWS FETCH NEXT @p2 ROWS ONLY
+""");
+    }
+
+    // The latest vector index version (required for VECTOR_SEARCH) is only available on Azure SQL (#36384).
+    [ConditionalFact]
+    [SqlServerCondition(SqlServerCondition.IsAzureSql)]
+    [Experimental("EF9105")]
+    public async Task VectorSearch_with_Take_and_Skip()
+    {
+        using var ctx = CreateContext();
+
+        var vector = new SqlVector<float>(new float[] { 1, 2, 100 });
+
+        var results = await ctx.VectorEntities
+            .VectorSearch(e => e.Vector, similarTo: vector, "cosine")
+            .Take(3)
+            .Skip(1)
+            .ToListAsync();
+
+        Assert.Equal(2, results.Count);
+
+        AssertSql(
+            """
+@p1='3'
+@p='Microsoft.Data.SqlTypes.SqlVector`1[System.Single]' (Size = 20) (DbType = Binary)
+@p2='1'
+
+SELECT [v1].[Id], [v1].[Distance]
+FROM (
+    SELECT TOP(@p1) WITH APPROXIMATE [v].[Id], [v0].[Distance]
+    FROM VECTOR_SEARCH(
+        TABLE = [VectorEntities] AS [v],
+        COLUMN = [Vector],
+        SIMILAR_TO = @p,
+        METRIC = 'cosine'
+    ) AS [v0]
+    ORDER BY [v0].[Distance]
+) AS [v1]
+ORDER BY [v1].[Distance]
+OFFSET @p2 ROWS
+""");
+    }
+
     [ConditionalFact]
     public async Task Length()
     {