Rebuild indexes when altering sparse SQL Server columns

[Copilot]

Altering a column to SPARSE fails when SQL Server indexes depend on that column. Migrations now recreate affected indexes around the column alteration.

• Migration SQL generation
  • Treat sparse annotation changes like narrowing/type changes for index rebuild purposes.
  • Drop dependent indexes before ALTER COLUMN and recreate them afterward.

DROP INDEX [IX_People_SomeProperty] ON [People];
ALTER TABLE [People] ALTER COLUMN [SomeProperty] nvarchar(450) SPARSE NULL;
CREATE INDEX [IX_People_SomeProperty] ON [People] ([SomeProperty]);

• Regression coverage
  • Added a SQL Server migration test for converting an indexed column to sparse.

• Fixes Unable to make a column sparse (in SQL Server) if it has an index #38760

[Copilot]

Pull request overview

This PR updates SQL Server migration SQL generation so that altering a column’s SPARSE setting will drop/recreate dependent indexes around ALTER COLUMN, avoiding SQL Server failures when indexes reference the altered column (fixing #38760).

Changes:

• Treat SPARSE annotation changes similarly to narrowing/type changes for index rebuild purposes in SqlServerMigrationsSqlGenerator.
• Generate DROP INDEX ... before ALTER TABLE ... ALTER COLUMN ... SPARSE ... and CREATE INDEX ... afterward.
• Add a SQL Server functional migration test covering converting an indexed column to sparse.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/EFCore.SqlServer/Migrations/SqlServerMigrationsSqlGenerator.cs	Triggers index rebuilds when the SPARSE annotation changes during AlterColumn.
test/EFCore.SqlServer.FunctionalTests/Migrations/MigrationsSqlServerTest.cs	Adds regression coverage asserting index drop/recreate around sparse column alteration.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/EFCore.SqlServer/Migrations/SqlServerMigrationsSqlGenerator.cs:325

• The newly added sparseChanged lines contain stray carriage-return characters (shown as in the file view), which introduces mixed line endings in this LF file. Please normalize these lines to the repository’s standard line endings to avoid noisy diffs and potential style checks failing.

        var sparseChanged = ((bool?)operation[SqlServerAnnotationNames.Sparse] ?? false)

            != ((bool?)operation.OldColumn[SqlServerAnnotationNames.Sparse] ?? false);

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[AndriySvyryd]

@cincuranet "Hide whitespace" when reviewing