| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | Jeff Ross <jross(at)wykids(dot)org>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Multiple table entries? |
| Date: | 2009-08-23 18:00:38 |
| Message-ID: | 29724.1251050438@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Greg Stark <gsstark(at)mit(dot)edu> writes:
> The last tuple is marked strangely I think. I don't think it's
> supposed to have XMAX_INVALID if xmax is 0 but I could be wrong. Also,
> I don't understand why it's marked as UPDATED if ctid and xmax aren't
> set.
No, that all looks right to me. UPDATE sets HEAP_UPDATED on the newer
version of the row, not the older one. What looks interesting to me is
that the last update isn't marked HEAP_ONLY_TUPLE, ie, it's not in the
same HOT chain. Why is that I wonder ...
> I'm wondering if the page allvisible flag is set. The visibility map
> is one of the few 8.4 patches which impact transaction visibility.
But we don't use that while examining individual tuples, do we?
regards, tom lane
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