Re: Patch: add timing of buffer I/O requests - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Patch: add timing of buffer I/O requests
Date
Msg-id 788.1334103410@sss.pgh.pa.us
Whole thread Raw
In response to Re: Patch: add timing of buffer I/O requests  (Peter Geoghegan <peter@2ndquadrant.com>)
Responses Re: Patch: add timing of buffer I/O requests  (Peter Geoghegan <peter@2ndquadrant.com>)
List pgsql-hackers
Peter Geoghegan <peter@2ndquadrant.com> writes:
> On 11 April 2012 00:35, Robert Haas <robertmhaas@gmail.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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