Re: Concurrent ALTER SEQUENCE RESTART Regression

On 4/24/17 15:52, Jason Petersen wrote:
> 1. Create a new sequence: CREATE SEQUENCE my_seq;
> 2. Start this loop twice in different shells:
> while true; do psql -1Xtc 'ALTER SEQUENCE my_seq RESTART 1'; done

> Each loop should repeatedly succeed and simply print ALTER SEQUENCE over and over.

> The output stream is punctuated by occasional "ERROR: tuple concurrently updated" messages.

This message comes from the pg_sequence catalog update. But in the case
of the RESTART clause, you don't need to update the catalog, because it
just needs to write to the sequence's relation. So I have tweaked the
code a little to omit the catalog update if it's not needed. Your test
case works without errors now.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services