Re: Adding percentile metrics to pg_stat_statements module

From: Adrien Nayrat <adrien(dot)nayrat(at)anayrat(dot)info>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Igor Calabria <igor(dot)calabria(at)gmail(dot)com>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Adding percentile metrics to pg_stat_statements module
Date: 2019-11-02 09:23:49
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On 10/31/19 8:32 PM, Tomas Vondra wrote:
> IMO having some sort of CDF approximation (being a q-digest or t-digest)
> would be useful, although it'd probably need to be optional (mostly
> becuase of memory consumption).

+1, I like this idea. If we are afraid of CPU cost we could imagine some kind of
sampling or add the possibility to collect only for a specific queryid.

I dreamed of this kind of feature for PoWA. Thus, it could make possible to
compare CDF between two days for example, before and after introducing a change.



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