Migration: Make existing column which has a unique index nullable fails

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
csharp
Domain
database

Research direction

Start by reproducing the migration that changes a non-nullable indexed column to nullable on the Microsoft.EntityFrameworkCore.SqlServer provider under .NET 5.0. Trace the generated migration operations and SQL for the column and unique index; done means the migration changes both without the SQL Server dependency error.

Written by the indexing model from the issue text.

Description

area-migrations customer-reported

Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: NET 5.0

When creating a unique index on a nullable column, the index is created with a 'where not null' clause. If however the column is not nullable, this is of course omitted. I'm now trying to change a column from 'not nullable' to 'nullable', containing such an index. This fails because the index isn't being altered either.

Microsoft.Data.SqlClient.SqlException
  HResult=0x80131904
  Message=The index 'UX_***************' is dependent on column '********'.
ALTER TABLE ALTER COLUMN *********** failed because one or more objects access this column.
Dominant language
C#
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