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From: Tom Lane <[email protected]>
To: Greg Hennessy <[email protected]>
Cc: [email protected]
Subject: Re: help debugging an issue with selectivity
Date: Tue, 17 Mar 2026 22:37:35 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CA+FnnTxGOqF1DN4e70KXRJakuPV_V7_vGonQTX4eEOEE92PCKw@mail.gmail.com>
	<CAKFQuwakY0c3x=2o=gQ6Cr7jQ=DgE_snL1cHf8Oj+irO1fmjEQ@mail.gmail.com>
	<[email protected]>

Greg Hennessy <[email protected]> writes:
> I am not sure if this belongs in pgsql-general or pgsql-hackers, I am 
> trying first in psgl-general.

Doesn't matter a lot, but as Rob noted, you should not hijack an
existing thread.  Start your own thread, don't reply to an unrelated
message.

> When I actually execute this, I get output to the terminal of the form:
> WARNING:  join_selectivity: operator id 16818 jointype 0 0
> WARNING:  HERE0 pgq3c_seljoin.... 5.873266e-12
> WARNING:  datum result 4438812783922730423 0.000000
> WARNING:  HERE0 pgq3c_seljoin.... 5.873266e-12
> WARNING:  join_selectivity: 0.000000 16818 jointype 0
> WARNING:  join_selectivity: s1 0.000000
> WARNING:  clause_selectivity: s1 0.000000

> where it seems to me the q3c code is returning a non zero value, but in 
> the guts of postgres what is found is a zero value.

I don't see any discrepancy in your results, only in your choices of
printf specifiers.  "%f" defaults to "%.6f", that is, print only six
digits after the decimal point.  So a value down around 1e-12 is
going to print as all zeroes.

			regards, tom lane

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