Re: pg_stat_statements and "IN" conditions

From: Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
To: David Steele <david(at)pgmasters(dot)net>
Cc: Zhihong Yu <zyu(at)yugabyte(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <stark(at)mit(dot)edu>, Pavel Trukhanov <pavel(dot)trukhanov(at)gmail(dot)com>
Subject: Re: pg_stat_statements and "IN" conditions
Date: 2021-09-30 13:49:30
Message-ID: 20210930134930.d4vzwhvxhfpk2zxt@localhost
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>On Wed, Jun 16, 2021 at 04:02:12PM +0200, Dmitry Dolgov wrote:
> > I've prepared a new rebased version to deal with the new way of
> > computing query id, but as always there is one tricky part. From what I
> > understand, now an external module can provide custom implementation for
> > query id computation algorithm. It seems natural to think this machinery
> > could be used instead of patch in the thread, i.e. one could create a
> > custom logic that will enable constants collapsing as needed, so that
> > same queries with different number of constants in an array will be
> > hashed into the same record.
> >
> > But there is a limitation in how such queries will be normalized
> > afterwards — to reduce level of surprise it's necessary to display the
> > fact that a certain query in fact had more constants that are showed in
> > pgss record. Ideally LocationLen needs to carry some bits of information
> > on what exactly could be skipped, and generate_normalized_query needs to
> > understand that, both are not reachable for an external module with
> > custom query id logic (without replicating significant part of the
> > existing code). Hence, a new version of the patch.
> Forgot to mention a couple of people who already reviewed the patch.

And now for something completely different, here is a new patch version.
It contains a small fix for one problem we've found during testing (one
path code was incorrectly assuming find_const_walker results).

Attachment Content-Type Size
v5-0001-Prevent-jumbling-of-every-element-in-ArrayExpr.patch text/x-diff 50.6 KB

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