This method is deprecated or moved on the latest stable version. The last existing version (v4.1.8) is shown here.
collation()
Returns the current database collation.
# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 216 def collation query( SELECT pg_database.datcollate FROM pg_database WHERE pg_database.datname LIKE '#{current_database}', 'SCHEMA')[0][0] end