Allow making a column non-nullable with SQL Server

Closes dotnet#21765

src/EFCore.SqlServer/Migrations/SqlServerMigrationsSqlGenerator.cs

@@ -343,6 +343,42 @@ protected override void Generate(
  (oldDefaultValue, oldDefaultValueSql) = (null, null);
  }
 
+ // The column is being made non-nullable. Generate an update statement before doing that, to convert any existing null values to
+ // the default value (otherwise SQL Server fails).
+ if (!operation.IsNullable
+ && operation.OldColumn.IsNullable
+ && (operation.DefaultValueSql is not null || operation.DefaultValue is not null))
+ {
+ string defaultValueSql;
+ if (operation.DefaultValueSql is not null)
+ {
+ defaultValueSql = operation.DefaultValueSql;
+ }
+ else
+ {
+ Check.DebugAssert(operation.DefaultValue is not null, "operation.DefaultValue is not null");
+
+ var typeMapping = (columnType != null
+ ? Dependencies.TypeMappingSource.FindMapping(operation.DefaultValue.GetType(), columnType)
+ : null)
+ ?? Dependencies.TypeMappingSource.GetMappingForValue(operation.DefaultValue);
+
+ defaultValueSql = typeMapping.GenerateSqlLiteral(operation.DefaultValue);
+ }
+
+ builder
+ .Append("UPDATE ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Table, operation.Schema))
+ .Append(" SET ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
+ .Append(" = ")
+ .Append(defaultValueSql)
+ .Append(" WHERE ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
+ .Append(" IS NULL")
+ .AppendLine(Dependencies.SqlGenerationHelper.StatementTerminator);
+ }
+
  if (alterStatementNeeded)
  {
  builder

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

@@ -690,6 +690,29 @@ public virtual Task Alter_column_make_required()
  Assert.False(column.IsNullable);
  });
 
+ [ConditionalFact]
+ public virtual Task Alter_column_make_required_with_null_data()
+ => Test(
+ builder => builder.Entity(
+ "People", e =>
+ {
+ e.Property<int>("Id");
+ e.Property<string>("SomeColumn");
+ e.HasData(new Dictionary<string, object>
+ {
+ { "Id", 1 },
+ { "SomeColumn", null }
+ });
+ }),
+ builder => { },
+ builder => builder.Entity("People").Property<string>("SomeColumn").IsRequired(),
+ model =>
+ {
+ var table = Assert.Single(model.Tables);
+ var column = Assert.Single(table.Columns, c => c.Name != "Id");
+ Assert.False(column.IsNullable);
+ });
+
  [ConditionalFact]
  public virtual Task Alter_column_make_required_with_index()
  => Test(

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

@@ -861,6 +861,23 @@ 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'SomeColumn');
 IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [People] SET [SomeColumn] = N'' WHERE [SomeColumn] IS NULL;
+ALTER TABLE [People] ALTER COLUMN [SomeColumn] nvarchar(max) NOT NULL;
+ALTER TABLE [People] ADD DEFAULT N'' FOR [SomeColumn];");
+ }
+
+ public override async Task Alter_column_make_required_with_null_data()
+ {
+ await base.Alter_column_make_required_with_null_data();
+
+ AssertSql(
+ @"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'SomeColumn');
+IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [People] SET [SomeColumn] = N'' WHERE [SomeColumn] IS NULL;
 ALTER TABLE [People] ALTER COLUMN [SomeColumn] nvarchar(max) NOT NULL;
 ALTER TABLE [People] ADD DEFAULT N'' FOR [SomeColumn];");
  }
@@ -878,6 +895,7 @@ 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'SomeColumn');
 IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [People] SET [SomeColumn] = N'' WHERE [SomeColumn] IS NULL;
 ALTER TABLE [People] ALTER COLUMN [SomeColumn] nvarchar(450) NOT NULL;
 ALTER TABLE [People] ADD DEFAULT N'' FOR [SomeColumn];
 CREATE INDEX [IX_People_SomeColumn] ON [People] ([SomeColumn]);");
@@ -896,6 +914,7 @@ 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'FirstName');
 IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [People] SET [FirstName] = N'' WHERE [FirstName] IS NULL;
 ALTER TABLE [People] ALTER COLUMN [FirstName] nvarchar(450) NOT NULL;
 ALTER TABLE [People] ADD DEFAULT N'' FOR [FirstName];
 CREATE INDEX [IX_People_FirstName_LastName] ON [People] ([FirstName], [LastName]);");
@@ -1127,6 +1146,7 @@ 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'SomeColumn');
 IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [People] SET [SomeColumn] = N'' WHERE [SomeColumn] IS NULL;
 ALTER TABLE [People] ALTER COLUMN [SomeColumn] nvarchar(450) NOT NULL;
 ALTER TABLE [People] ADD DEFAULT N'' FOR [SomeColumn];
 CREATE INDEX [IX_People_SomeColumn] ON [People] ([SomeColumn]) INCLUDE ([SomeOtherColumn]);");
@@ -2053,6 +2073,7 @@ 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'SomeField');
 IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [People] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [People] SET [SomeField] = N'' WHERE [SomeField] IS NULL;
 ALTER TABLE [People] ALTER COLUMN [SomeField] nvarchar(450) NOT NULL;
 ALTER TABLE [People] ADD DEFAULT N'' FOR [SomeField];",
  //
@@ -7921,6 +7942,7 @@ 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'[Entity]') AND [c].[name] = N'Name');
 IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [Entity] DROP CONSTRAINT [' + @var0 + '];');
+UPDATE [Entity] SET [Name] = N'' WHERE [Name] IS NULL;
 ALTER TABLE [Entity] ALTER COLUMN [Name] nvarchar(max) NOT NULL;
 ALTER TABLE [Entity] ADD DEFAULT N'' FOR [Name];");
  }