On Sat, Jun 7, 2014 at 1:28 AM, Andres Freund <and...@2ndquadrant.com>
> On 2014-06-06 15:44:25 -0400, Tom Lane wrote:
> > I figured it'd be easy enough to get a better estimate by adding another
> > counter to count just LIVE and INSERT_IN_PROGRESS tuples (thus
> > assuming that in-progress inserts and deletes will both commit).  I did
> > that, and found that it helped Tim's test case not at all :-(.  A bit of
> > sleuthing revealed that HeapTupleSatisfiesVacuum actually returns
> > INSERT_IN_PROGRESS for any tuple whose xmin isn't committed, regardless
> > whether the transaction has since marked it for deletion:
> >
> >             /*
> >              * It'd be possible to discern between INSERT/DELETE in
> >              * here by looking at xmax - but that doesn't seem
beneficial for
> >              * the majority of callers and even detrimental for some.
> >              * rather have callers look at/wait for xmin than xmax. It's
> >              * always correct to return INSERT_IN_PROGRESS because
> >              * what's happening from the view of other backends.
> >              */
> >             return HEAPTUPLE_INSERT_IN_PROGRESS;
> That's only the case of a couple of days ago. I really wasn't sure
> wheter to go that way or discern the two cases. That changed in the wake
> of:
> http://www.postgresql.org/message-id/20140530143150.GA11051@localhost

Won't this change impact the calculation of number of live
rows for analyze (acquire_sample_rows() considers the


for tuples updated by transactions other than current transaction)?

Even if we think that estimates are okay, the below comment

in acquire_same_rows() doesn't seem to suggest it.

 * We count delete-in-progress rows as still live, using
 * the same reasoning given above; but we don't bother to
 * include them in the sample.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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