| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Ants Aasma <ants(dot)aasma(at)eesti(dot)ee>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Kevin Grittner <kgrittn(at)postgresql(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, "pgsql-committers(at)postgresql(dot)org" <pgsql-committers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < |
| Date: | 2016-06-16 02:43:05 |
| Message-ID: | 20160616024305.GA44021@alvherre.pgsql |
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| Lists: | pgsql-committers pgsql-hackers |
Kevin Grittner wrote:
> test=# -- connection 1
> analyze verbose t1; -- when run after threshold, STO error occurs
> INFO: analyzing "public.t1"
> INFO: "t1": scanned 45 of 45 pages, containing 8999 live rows and
> 1001 dead rows; 8999 rows in sample, 8999 estimated total rows
> ERROR: snapshot too old
> CONTEXT: SQL statement "SELECT (i * (select c1 from t2))"
> PL/pgSQL function mysq(integer) line 3 at RETURN
>
> Is there some other behavior which would be preferred?
The fact that the ERROR is being thrown seems okay to me. I was a bit
surprised that the second INFO line is shown, but there's a simple
explanation: we first acquire the sample rows (using
acquire_sample_rows) and only after that's done we try to compute the
stats from them.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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