maximum name length not specified for PostgreSQL
|Reported by:||Andrew Ball||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||master|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
Neither the postgresql nor postgresql_psycopg2 database backends implement the DatabaseOperations.max_name_length() method. Issue #13434 contains changeset () that implements the corresponding method for the MySQL database backend, thus preventing the BaseDatabaseCreation class's sql_indices_for_field() method from trying to make indices in MySQL with names that are too long. The same fix should work for PostgreSQL, given a suitable max_name_length() implementation.
Generally, the maximum identifier length in PostgreSQL is 63, but it may be changed by recompiling PostgreSQL with the NAMEDATALEN macro in src/include/pg_config_manual.h changed. Note that the maximum identifier length is always one less than the value of that macro.
I've made a patch that just returns 63 in both PostgreSQL backends, with a docstring explaining about the possibility of recompiling PostgreSQL and suggesting that someone who has recompiled PostgreSQL and wants a different maximum name length could make their own database backend by inheriting almost everything from one of the existing backends and overridding the max_name_length() method in the database operations class.