Question

I ran into the problem that my primary key sequence is not in sync with my table rows.

That is, when I insert a new row I get a duplicate key error because the sequence implied in the serial datatype returns a number that already exists.

It seems to be caused by import/restores not maintaining the sequence properly.

Answer 1

-- Login to psql and run the following  -- What is the result? SELECT MAX(id) FROM your_table;  -- Then run... -- This should be higher than the last result. SELECT nextval('your_table_id_seq');  -- If it's not higher... run this set the sequence last to your highest id.  -- (wise to run a quick pg_dump first...)  BEGIN; -- protect against concurrent inserts while you update the counter LOCK TABLE your_table IN EXCLUSIVE MODE; -- Update the sequence SELECT setval('your_table_id_seq', COALESCE((SELECT MAX(id)+1 FROM your_table), 1), false); COMMIT; 

Source – Ruby Forum