Re: [BUGS] Concurrent ALTER SEQUENCE RESTART Regression

On 4/25/17 00:26, Michael Paquier wrote:
> So things are broken for sequences since commit 1753b1b0 (adding Peter
> in CC) that has changed the way sequence metadata is handled. The
> failure happens in CatalogTupleUpdate() which uses
> simple_heap_update() that caller can only use if updates are
> concurrent safe. But since 1753b1b0 that is not true as the sequence
> is locked with AccessShareLock.

I think you are confusing locking the sequence versus locking the
pg_sequence catalog.  The error is coming from CatalogTupleUpdate() on
pg_sequence, which is locked using RowExclusiveLock, which is what we
use for most DDL commands doing catalog changes.

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


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