From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Peter Geoghegan <peter(at)2ndquadrant(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Ants Aasma <ants(at)cybertec(dot)at>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Patch: add timing of buffer I/O requests |
Date: | 2012-04-11 00:16:50 |
Message-ID: | 788.1334103410@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Peter Geoghegan <peter(at)2ndquadrant(dot)com> writes:
> On 11 April 2012 00:35, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> If people need something like that, couldn't they create it by hashing
>> the normalized query text with an arbitrary algorithm?
> That supposes that the normalised query text is perfectly stable. It
> may well not be, particularly for things like ad-hoc queries or
> queries generated by ORMs, across database clusters and over long
> periods of time -
Indeed, but the hash value isn't stable either given those sorts of
assumptions, so I'm not convinced that there's any advantage there.
What I think people would actually like to know, if they're in a
situation where distinct query texts are getting hashed to the same
thing, is *which* different texts got hashed to the same thing.
But there's no good way to expose that given the pg_stat_statements
infrastructure, and exposing the hash value doesn't help.
regards, tom lane
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