Added support for computed columns

[aidanharan]

Added support for computed columns (#1346).

create_table :users do |t|
    t.string :name
    t.virtual :lower_name, as: "LOWER(name)", stored: false
    t.virtual :upper_name, as: "UPPER(name)", stored: true
    t.virtual :name_length, as: "LEN(name)"
end

Computed columns can be virtual stored: false (default) or persisted stored: true.

Ref:

• https://learn.microsoft.com/en-us/sql/relational-databases/tables/specify-computed-columns-in-a-table?view=sql-server-ver17
• Add support for generated columns in SQLite3 adapter rails/rails#49346
• Support virtual (not persisted) generated columns on PostgreSQL 18+ rails/rails#55142

[Copilot]

Pull Request Overview

This PR adds support for computed columns in SQL Server, allowing developers to define virtual columns with computed expressions that can be either virtual (not stored) or persisted (stored). The implementation follows SQL Server's computed column syntax and integrates with Rails' Active Record column definition system.

Key changes:

• Added virtual column support with t.virtual syntax in table definitions
• Implemented computed column detection and metadata extraction from SQL Server system tables
• Enhanced schema dumping to preserve virtual column definitions

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/cases/virtual_column_test_sqlserver.rb	Comprehensive test suite for virtual column functionality
test/cases/coerced_tests.rb	Added :as and :stored as valid column options
lib/active_record/connection_adapters/sqlserver_column.rb	Extended Column class with virtual column support methods
lib/active_record/connection_adapters/sqlserver_adapter.rb	Added supports_virtual_columns? capability
lib/active_record/connection_adapters/sqlserver/table_definition.rb	Added virtual column options to table definition
lib/active_record/connection_adapters/sqlserver/schema_statements.rb	Enhanced column metadata extraction for computed columns
lib/active_record/connection_adapters/sqlserver/schema_dumper.rb	Added virtual column dumping support and fixed typo
lib/active_record/connection_adapters/sqlserver/schema_creation.rb	Added SQL generation for virtual column definitions
CHANGELOG.md	Added entry for computed columns feature

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[ttilberg]

Yeah!

This also closes #1346