When using postgres locally for development, sometimes, if the production dataset is too large, I'll take a sample to work with locally.
More recently I've run into the problem that when I load new production data into tables with auto increment primary key columns, I'll get a conflict, i.e. I load some production data in locally, and then when the auto increment runs it'll hit a conflict - because my local sequences are completely out of sync with production.
The solution is to update my local sequence value. This is a two part process.
1. Capture current values from production:
SELECT last_value FROM public.<table>_<col>_seq;
So for something like user ids, this would be:
SELECT last_value FROM public.user_id_seq; >>> 304
If this doesn't yield a result, then the sequence name is wrong, and it can be checked with the following query:
SELECT pg_get_serial_sequence('user', 'id');
Now armed with this value, in my example
304, the next part is to upload locally:
2. Update sequences locally:
ALTER SEQUENCE <table>_<col>_seq RESTART WITH <next_value>;
It's important that I update to the next value, not the current value:
ALTER SEQUENCE user_id_seq RESTART WITH 305;
Now when the next id for the user is loaded through an insert, the sequences are in sync.