Fix Rails 8.1 compatibility for Column#initialize signature

[pfeffer]

Hi @januszm! I ran into this issue when upgrading to Rails 8.1.2 - could you please take a look?

Summary

Rails 8.1 changed Column#initialize to require cast_type as the second argument, breaking schema
loading.

Error:

  NoMethodError: undefined method 'mutable?' for nil (NoMethodError)
      @default = default.nil? || cast_type.mutable? ? default : cast_type.deserialize(default)

Stack trace:

  active_record/connection_adapters/column.rb:25:in initialize
  active_record/connection_adapters/redshift_8_0/column.rb:13:in initialize
  active_record/connection_adapters/redshift_8_0/schema_statements.rb:160:in new_column
  active_record/connection_adapters/redshift_8_0/schema_statements.rb:155:in block in columns
  active_record/model_schema.rb:609:in load_schema!
  active_record/core.rb:319:in block in find_by

Root cause

# Rails 8.0
def initialize(name, default, sql_type_metadata, null, ...)

# Rails 8.1
def initialize(name, cast_type, default, sql_type_metadata, null, ...)

The adapter passes default where Rails 8.1 expects cast_type, so cast_type.mutable? is called on nil.

Fix

• Conditionally define RedshiftColumn#initialize based on Rails version
• Pass cast_type through columns() → new_column() → RedshiftColumn.new()
• Maintains backwards compatibility with Rails 8.0

Tested

• Rails 8.1.2 - schema loading works
• Rails 8.0 - backwards compatible