Fixed error when folding single-record joins to nested loop

MarkMpn · Nov 15, 2024 · 5762636 · 5762636
1 parent d8105b1
commit 5762636
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Showing 3 changed files with 37 additions and 6 deletions.
diff --git a/MarkMpn.Sql4Cds.Engine.Tests/ExecutionPlanTests.cs b/MarkMpn.Sql4Cds.Engine.Tests/ExecutionPlanTests.cs
@@ -4761,18 +4761,19 @@ public void MetadataLeftJoinData()
             var nestedLoop = AssertNode<NestedLoopNode>(select.Source);
             Assert.AreEqual(QualifiedJoinType.LeftOuter, nestedLoop.JoinType);
             Assert.AreEqual(1, nestedLoop.OuterReferences.Count);
-            Assert.AreEqual("@Cond1", nestedLoop.OuterReferences["entity.metadataid"]);
+            var outerReference = nestedLoop.OuterReferences["entity.metadataid"];
+            Assert.IsTrue(outerReference.StartsWith("@Cond"));
             var meta = AssertNode<MetadataQueryNode>(nestedLoop.LeftSource);
             var fetch = AssertNode<FetchXmlScan>(nestedLoop.RightSource);
-            AssertFetchXml(fetch, @"
+            AssertFetchXml(fetch, $@"
                 <fetch xmlns:generator='MarkMpn.SQL4CDS'>
                     <entity name='account'>
                         <attribute name='name' />
                         <link-entity name='contact' alias='contact' from='contactid' to='primarycontactid' link-type='outer'>
                             <attribute name='firstname' />
                         </link-entity>
                         <filter>
-                            <condition attribute='accountid' operator='eq' value='@Cond1' generator:IsVariable='true' />
+                            <condition attribute='accountid' operator='eq' value='{outerReference}' generator:IsVariable='true' />
                         </filter>
                     </entity>
                 </fetch>");
@@ -7442,7 +7443,7 @@ public void MistypedJoinCriteriaGeneratesWarning()
             var select = AssertNode<SelectNode>(plans[0]);
             var loop = AssertNode<NestedLoopNode>(select.Source);
             Assert.IsNull(loop.JoinCondition);
-            Assert.AreEqual("No Join Predicate", loop.Warning);
+            Assert.AreEqual("No Join Predicate or Outer References", loop.Warning);
             var accountFetch = AssertNode<FetchXmlScan>(loop.LeftSource);
 
             AssertFetchXml(accountFetch, @"
@@ -8672,5 +8673,31 @@ public void InVariables()
     </entity>
 </fetch>");
         }
+
+        [TestMethod]
+        public void FoldSingleRowJoinToNestedLoop()
+        {
+            // https://github.com/MarkMpn/Sql4Cds/issues/582
+            var planBuilder = new ExecutionPlanBuilder(new SessionContext(_localDataSources, this), this);
+
+            var query = @"
+SELECT TOP 10 a.name,
+              e.logicalname
+FROM account AS a 
+     INNER JOIN
+     metadata.entity e
+     ON a.accountid = e.metadataid
+WHERE a.accountid = '9B8AAC69-EECA-497A-99AB-C65B9E702D89'";
+
+            var plans = planBuilder.Build(query, null, out _);
+
+            Assert.AreEqual(1, plans.Length);
+
+            var select = AssertNode<SelectNode>(plans[0]);
+            var top = AssertNode<TopNode>(select.Source);
+            var loop = AssertNode<NestedLoopNode>(top.Source);
+            var fetch = AssertNode<FetchXmlScan>(loop.LeftSource);
+            var meta = AssertNode<MetadataQueryNode>(loop.RightSource);
+        }
     }
 }
diff --git a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/FoldableJoinNode.cs b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/FoldableJoinNode.cs
@@ -821,7 +821,11 @@ private bool FoldSingleRowJoinToNestedLoop(NodeCompilationContext context, IList
                     SecondExpression = new VariableReference { Name = outerReference }
                 }
             };
-            var foldedRightSource = filteredRightSource.FoldQuery(context, hints);
+            var contextWithOuterReference = context.CreateChildContext(new Dictionary<string, DataTypeReference>
+            {
+                [outerReference] = leftSchema.Schema[leftAttr].Type
+            });
+            var foldedRightSource = filteredRightSource.FoldQuery(contextWithOuterReference, hints);
 
             // If we can't fold the filter down to the data source, there's no benefit from doing this so stick with the
             // original join type

diff --git a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/NestedLoopNode.cs b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/NestedLoopNode.cs
@@ -32,7 +32,7 @@ class NestedLoopNode : BaseJoinNode, IExecutionPlanNodeWarning
         public Dictionary<string,string> OuterReferences { get; set; }
 
         [Browsable(false)]
-        public string Warning => JoinCondition == null ? "No Join Predicate" : null;
+        public string Warning => JoinCondition == null && (OuterReferences == null || OuterReferences.Count == 0) ? "No Join Predicate or Outer References" : null;
 
         protected override IEnumerable<Entity> ExecuteInternal(NodeExecutionContext context)
         {