Schema dump writes create_collation after tables

[jeremysmithco]

Hey, thanks for this gem! I just had this issue on a project and started looking for a solution yesterday, so this was good timing! 😊

I noticed when running rails db:schema:dump that the create_collation calls will get added near the end of the schema.rb, after the table definitions:

ActiveRecord::Schema[8.2].define(version: 2025_10_13_182247) do
  enable_extension "fuzzystrmatch"
  enable_extension "pg_catalog.plpgsql"
  enable_extension "pg_stat_statements"
  enable_extension "pg_trgm"
  enable_extension "pgcrypto"
  enable_extension "tablefunc"
  
  # …

  create_table "xxx", force: :cascade do |t|
    # …
    
    t.string "xxx_number", collation: "numeric"
    
    # …
  end

  # …

  create_collation("numeric", "en-u-kn")
end

And so when I try to load the schema again, I get an error at the first point where I try to use a named collation, because it doesn't exist yet:

bin/rails aborted!
ActiveRecord::StatementInvalid: PG::UndefinedObject: ERROR:  collation "numeric" for encoding "UTF8" does not exist (ActiveRecord::StatementInvalid)
LINE 1: ...cter varying, "xxx_number" character varying COLLATE "n...
                                                             ^
/Users/jeremy/Code/xxx/db/schema.rb:618:in 'block in <main>'
/Users/jeremy/Code/xxx/db/schema.rb:13:in '<main>'

Caused by:
PG::UndefinedObject: ERROR:  collation "numeric" for encoding "UTF8" does not exist (PG::UndefinedObject)
LINE 1: ...cter varying, "xxx_number" character varying COLLATE "n...
                                                             ^
/Users/jeremy/Code/xxx/db/schema.rb:618:in 'block in <main>'
/Users/jeremy/Code/xxx/db/schema.rb:13:in '<main>'
Tasks: TOP => db:setup => db:schema:load

There's another gem out there (older, apparently unmaintained) called activerecord-pg_collation and I noticed that it creates collations right after extensions, which makes sense to me:

module SchemaDumper
  private

  def extensions(stream)
    super
    collations(stream)
  end

  # …
end

I also noticed it uses prepend instead of include:

ActiveRecord::ConnectionAdapters::PostgreSQL::SchemaDumper.prepend(SchemaDumper)

What would you think of that change? Am I missing anything important? Thanks!