Add test coverage for index recreation

test/EFCore.Relational.Specification.Tests/Migrations/MigrationsTestBase.cs

@@ -779,6 +779,38 @@ public virtual Task Alter_column_change_computed()
                     }
                 });
 
+        [ConditionalFact]
+        public virtual Task Alter_column_change_computed_recreates_indexes()
+            => Test(
+                builder => builder.Entity(
+                    "People", e =>
+                    {
+                        e.Property<int>("Id");
+                        e.Property<int>("X");
+                        e.Property<int>("Y");
+                        e.Property<int>("Sum");
+
+                        e.HasIndex("Sum");
+                    }),
+                builder => builder.Entity("People").Property<int>("Sum")
+                    .HasComputedColumnSql($"{DelimitIdentifier("X")} + {DelimitIdentifier("Y")}"),
+                builder => builder.Entity("People").Property<int>("Sum")
+                    .HasComputedColumnSql($"{DelimitIdentifier("X")} - {DelimitIdentifier("Y")}"),
+                model =>
+                {
+                    var table = Assert.Single(model.Tables);
+                    var sumColumn = Assert.Single(table.Columns, c => c.Name == "Sum");
+                    if (AssertComputedColumns)
+                    {
+                        Assert.Contains("X", sumColumn.ComputedColumnSql);
+                        Assert.Contains("Y", sumColumn.ComputedColumnSql);
+                        Assert.Contains("-", sumColumn.ComputedColumnSql);
+                    }
+
+                    var sumIndex = Assert.Single(table.Indexes);
+                    Assert.Collection(sumIndex.Columns, c => Assert.Equal("Sum", c.Name));
+                });
+
         [ConditionalFact]
         public virtual Task Alter_column_change_computed_type()
             => Test(

test/EFCore.SqlServer.FunctionalTests/Migrations/MigrationsSqlServerTest.cs

@@ -635,6 +635,23 @@ public override async Task Alter_column_change_computed()
 ALTER TABLE [People] ADD [Sum] AS [X] - [Y];");
         }
 
+        public override async Task Alter_column_change_computed_recreates_indexes()
+        {
+            await base.Alter_column_change_computed_recreates_indexes();
+
+            AssertSql(
+                @"DROP INDEX [IX_People_Sum] ON [People];
+DECLARE @var0 sysname;
+SELECT @var0 = [d].[name]
+FROM [sys].[default_constraints] [d]
+INNER JOIN [sys].[columns] [c] ON [d].[parent_column_id] = [c].[column_id] AND [d].[parent_object_id] = [c].[object_id]
+WHERE ([d].[parent_object_id] = OBJECT_ID(N'[People]') AND [c].[name] = N'Sum');
+IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+ALTER TABLE [People] DROP COLUMN [Sum];
+ALTER TABLE [People] ADD [Sum] AS [X] - [Y];",
+                @"CREATE INDEX [IX_People_Sum] ON [People] ([Sum]);");
+        }
+
         public override async Task Alter_column_change_computed_type()
         {
             await base.Alter_column_change_computed_type();

test/EFCore.Sqlite.FunctionalTests/Migrations/MigrationsSqliteTest.cs

@@ -430,6 +430,27 @@ public override async Task Alter_column_change_computed()
                 @"PRAGMA foreign_keys = 1;");
         }
 
+        public override async Task Alter_column_change_computed_recreates_indexes()
+        {
+            await base.Alter_column_change_computed_recreates_indexes();
+
+            AssertSql(
+                @"CREATE TABLE ""ef_temp_People"" (
+    ""Id"" INTEGER NOT NULL,
+    ""Sum"" AS (""X"" - ""Y""),
+    ""X"" INTEGER NOT NULL,
+    ""Y"" INTEGER NOT NULL
+);",
+                @"INSERT INTO ""ef_temp_People"" (""Id"", ""X"", ""Y"")
+SELECT ""Id"", ""X"", ""Y""
+FROM ""People"";",
+                @"PRAGMA foreign_keys = 0;",
+                @"DROP TABLE ""People"";",
+                @"ALTER TABLE ""ef_temp_People"" RENAME TO ""People"";",
+                @"PRAGMA foreign_keys = 1;",
+                @"CREATE INDEX ""IX_People_Sum"" ON ""People"" (""Sum"");");
+        }
+
         public override async Task Alter_column_change_computed_type()
         {
             await base.Alter_column_change_computed_type();