| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Minimum tuple threshold to decide last pass of VACUUM |
| Date: | 2015-08-03 16:36:03 |
| Message-ID: | 9149.1438619763@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> Simon Riggs wrote:
>> * For emergency anti-wraparound VACUUMs we shouldn't scan indexes at all,
>> since they aren't critical path activities at that point
> It is not possible to skip scanning indexes completely, unless no tuples
> are to be removed from the heap.
Right.
> But actually this is an interesting point and I don't think we do this:
> if in emergency mode, maybe we shouldn't try to remove any dead tuples
> at all, and instead only freeze very old tuples.
+1 ... not sure if that's what Simon had in mind exactly, but it seems
like a correct statement of what he was getting at.
regards, tom lane
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