This method is deprecated or moved on the latest stable version.
The last existing version (v4.1.8) is shown here.
schema_names()
public
Returns an array of schema names.
# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 230
def schema_names
query( SELECT nspname FROM pg_namespace WHERE nspname !~ '^pg_.*' AND nspname NOT IN ('information_schema') ORDER by nspname;, 'SCHEMA').flatten
end