Horton

Re: explain analyze rows=%.0f

Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>

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From: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andrei Lepikhov <lepihov@gmail.com>, pgsql-hackers@lists.postgresql.org, Guillaume Lelarge <guillaume@lelarge.info>, Matheus Alcantara <matheusssilv97@gmail.com>, Alena Rybakina <a.rybakina@postgrespro.ru>
Date: 2025-03-11T09:58:06Z
Lists: pgsql-hackers 
Hi,

In the stats_ext regression test, there is a function 
check_estimated_rows that returns actual rows as an integer. Currently, 
none of the test cases produce a non-zero fractional part in actual rows.

The question is: should this function be modified to return a fractional 
number instead of an integer?

Personally, I don’t see much value in doing so, because the purpose of 
the test is to compare the estimated row count with the actual number of 
rows. It is also unlikely that there will be test cases where loops > 1, 
and the presence of a fractional part does not change the essence of the 
test.

What do you think?

--
Best regards,
Ilia Evdokimov,
Tantor Labs LLC.

Commits

  1. EXPLAIN: Always use two fractional digits for row counts.

  2. Adjust EXPLAIN test case to filter out "Actual Rows" values.

  3. Allow EXPLAIN to indicate fractional rows.

  4. Fix pgbench performance issue induced by commit af35fe501.