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From: Sami Imseih <[email protected]>
To: Michael Paquier <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: [email protected]
Cc: [email protected]
Subject: Re: Improve pg_stat_statements scalability
Date: Tue, 2 Jun 2026 18:53:43 -0500
Message-ID: <CAA5RZ0s17LnC+31V6=qTrnJGjz7OLb+mkw4dMeiZM6bUOymoxw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAP53PkyWD99bNwFVv2KibfL4bhm-D78QAnc9UqQQJdtJ3mQWPQ@mail.gmail.com>
	<CAA5RZ0sQ+gDn-J85j1FzOdL1YjVYRegpmQpDiah1=REWZSZj+Q@mail.gmail.com>
	<CAA5RZ0uoxiQ2_=xHGRnyc4WdM9aR0fzdMhBubnw97po==--yGQ@mail.gmail.com>
	<[email protected]>
	<[email protected]>

> > As far as I can see, the current implementation does not apply any
> > throttling to calls of this API. In theory, a large number of backends
> > could invoke it frequently and generate a high flush rate. For
> > example, if 1000 backends were to call it once per second, that would
> > result in 1000 shared-stats updates per second.
> >
> > Whether such a usage pattern would occur in practice is a separate
> > question. However, given that existing pgstat code uses
> > PGSTAT_MIN_INTERVAL to limit flush frequency, it seems to me that
> > anytime stats should probably retain a similar restriction.
>
> Hmm, OK.  One cost in this decision is that it could randomly make the
> tests randomly slower, which is one reason why this patch has been
> added to this thread.

The throttling does make the tests longer, but we can do similar to what
was done in f1e251be80a, and disable PGSTAT_MIN_INTERVAL if
injection points are enabled.

-       /* 50 tries with 100ms sleep between tries makes 5 sec total wait */
-       for (tries = 0; tries < 50; tries++)
+       /*
+        * Retry up to 50 times with 100ms between attempts (max 5s
total). Can be
+        * reduced to 3 attempts (max 0.3s total) to speed up tests.
+        */
+       int                     ntries = 50;
+
+#ifdef USE_INJECTION_POINTS
+       if (IS_INJECTION_POINT_ATTACHED("procarray-reduce-count"))
+               ntries = 3;
+#endif
+

--
Sami Imseih
Amazon Web Services (AWS)

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  Subject: Re: Improve pg_stat_statements scalability
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