Web2py - Key/constraint issue when using separate SQL database for archiving

Question

In a web2py application, I've got a primary postgresql database (db1), and I've set up a separate postgresql database (db1_archive) used for archiving several of the tables from db1. This functionality is implemented in a module with the following:

class db_archives():

    def __init__(self, request, response, db1_archive, db1, auth):

        ...

        auth.enable_record_versioning(
            archive_db = db1_archive,
            tables = [db1.auth_user, db1.table1, db1.table2, ...]
            archive_names='archive_%(tablename)s'
            )

When something is deleted from the relevant tables in db1, it should automatically be archived in db1_archive. However, upon deletion, the following psycopg2.IntegrityError is produced instead:

insert or update on table "archive_table1" violates foreign key constraint "archive_table1_created_by_fkey" DETAIL: Key (created_by)=(9) is > not present in table "auth_user"

I guess what's happening is that the archive DB is not finding a user with an ID of 9. The 'created_by' field has the following constraint:

FOREIGN KEY (created_by) REFERENCES auth_user(id) ON DELETE CASCADE

I'd like to remove all constraints from the archive db. I think this can be done with web2py's [database_name].executesql() function. However, I've tried a few things such as db1_archive.executesql('SET FOREIGN_KEY_CHECKS=0;') , and only ended up with error messages. Can anyone advise me on some SQL or web2py codes I could try to fix the situation? Thanks.

Answer 1

What you need to do is build a list of the constraint names and then walk through them in your code and:

alter table [tablename] drop constraint [fkeyname];

If you need to pull this info from the system catalogs, see the pg_constraint table.

Please note that alter table cannot be parameterized so you will have to assemble the command as a string with proper escaping and run it.