| From: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Allow "snapshot too old" error, to prevent bloat |
| Date: | 2015-02-24 13:17:34 |
| Message-ID: | 126750886.2716764.1424783854878.JavaMail.yahoo@mail.yahoo.com |
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| Lists: | pgsql-hackers |
Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> Could you please explain in slightly more detail why can't it work> if we use timestamp instead of snapshot->xmin in your patch in
> function TestForOldSnapshot()?
It works fine for the additional visibility checking in scans, but
it doesn't cover the vacuuming -- that needs to use a transaction ID
for its cutoff.
> How exactly will this allow to return "snapshot old" error, do we
> need a check for page (page lsn) as in your current patch?
The change to the part where it actually throws the error is very
small, just checking time instead of xmin.
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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