| From: | Peter Geoghegan <peter(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Ants Aasma <ants(at)cybertec(dot)at>, Greg Smith <greg(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Patch: add timing of buffer I/O requests |
| Date: | 2012-04-14 13:54:39 |
| Message-ID: | CAEYLb_V+a8FoAxCNZYg=dP4s1zVVPqmkMzkTxWsqP9M8N4j7aw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 10 April 2012 19:10, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Hmm. Maybe we should think about numeric ms, which would have all the
>> same advantages but without the round-off error.
>
> Color me unimpressed ... numeric calculations are vastly more expensive
> than float, and where are you going to get timing data that has more
> than sixteen decimal digits of accuracy?
+1
Besides, how do you propose to solve the problem of storing numerics
in a fixed allocation of shared memory? The only comparable thing in
pg_stat_statements is the query string, which is capped at
track_activity_query_size bytes for this very reason.
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services
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