Fix so views can be used in views (#191)

src/FlowtideDotNet.Substrait/PlanModifier.cs

@@ -109,6 +109,21 @@ public Plan Modify()
             }
             var modifierVisitor = new ModifierVisitor(subPlanNameToId);
 
+            for (int i = 0; i < newPlan.Relations.Count; i++)
+            {
+                var relation = newPlan.Relations[i];
+                if (relation is RootRelation rootRelation)
+                {
+                    var modified = modifierVisitor.Visit(rootRelation.Input, default);
+                    newPlan.Relations[i] = modified;
+                }
+                else
+                {
+                    var modified = modifierVisitor.Visit(relation, default);
+                    newPlan.Relations[i] = modified;
+                }
+            }
+
             var rootRelationId = -1;
             RootRelation? oldRootRel = null;
             for (int i = 0; i < _rootPlan.Relations.Count; i++)

tests/FlowtideDotNet.AcceptanceTests/ViewTests.cs

@@ -0,0 +1,55 @@
+// Licensed under the Apache License, Version 2.0 (the "License")
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//  
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Xunit.Abstractions;
+
+namespace FlowtideDotNet.AcceptanceTests
+{
+    public class ViewTests : FlowtideAcceptanceBase
+    {
+        public ViewTests(ITestOutputHelper testOutputHelper) : base(testOutputHelper)
+        {
+        }
+
+        [Fact]
+        public async Task TestViewInView()
+        {
+            GenerateData();
+
+            await StartStream(@"
+             CREATE VIEW test AS
+                SELECT 
+                    userKey, 
+                    firstName
+                FROM users;
+
+            CREATE VIEW test2 AS
+                SELECT 
+                    userKey, 
+                    firstName
+                FROM test;
+
+            INSERT INTO output
+            SELECT userKey, firstName FROM test2;
+            ");
+
+            await WaitForUpdate();
+
+            AssertCurrentDataEqual(Users.Select(u => new { u.UserKey, u.FirstName }).ToList());
+        }
+    }
+}