On 2014-10-18 14:30:53 -0400, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.com> writes:
> > Interestingly we already set PROC_IN_ANALYZE - but we never actually
> > look at it. I wonder what it'd take to ignore analyze in
> > GetSnapshotData()/GetOldestXmin()... At first sight it looks quite
> > doable to not have a snapshot around (or setup to be ignored) while
> > acquire_sample_rows() is running. As that's the expensive bit...
>
> Say what? How is ANALYZE supposed to know which rows are valid
> without a snapshot?
I haven't fully investigated it yet. But it's already not using it's own
snapshot to determine visibility. Instead it uses GetOldestXmin() +
HeapTupleSatisfiesVacuum().
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services
