Re: MVCC catalog access

On Thu, May 30, 2013 at 1:39 AM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> +1.

Here's a more serious patch for MVCC catalog access.  This one
involves more data copying than the last one, I think, because the
previous version did not register the snapshots it took, which I think
is not safe.  So this needs to be re-tested for performance, which I
have so far made no attempt to do.

It strikes me as rather unfortunate that the snapshot interface is
designed in such a way as to require so much data copying.  It seems
we always take a snapshot by copying from PGXACT/PGPROC into
CurrentSnapshotData or SecondarySnapshotData, and then copying data a
second time from there to someplace more permanent.  It would be nice
to avoid that, at least in common cases.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company