Re: EXPLAIN (ANALYZE, BUFFERS) - puzzling numbers for a simple query. - Mailing list pgsql-general

From Laurenz Albe
Subject Re: EXPLAIN (ANALYZE, BUFFERS) - puzzling numbers for a simple query.
Date
Msg-id fd14173d698cf45d5784c459f63a982aa800b9e6.camel@cybertec.at
Whole thread Raw
In response to Re: EXPLAIN (ANALYZE, BUFFERS) - puzzling numbers for a simple query.  (David Rowley <dgrowleyml@gmail.com>)
Responses Re: EXPLAIN (ANALYZE, BUFFERS) - puzzling numbers for a simple query.  (David Rowley <dgrowleyml@gmail.com>)
Re: EXPLAIN (ANALYZE, BUFFERS) - puzzling numbers for a simple query.  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
On Sat, 2021-06-05 at 00:12 +1200, David Rowley wrote:
> As for the call to generate_series, you're not likely to ever get any
> great estimation from that.  The number of rows returned by a call to
> that particular function are just whatever is set in pg_proc.prorows,
> in this case, 1000.  The other generate_series functions which take
> INT and BIGINT inputs do have a prosupport function.

"generate_series" has a support function from v12 on:

EXPLAIN SELECT * FROM generate_series(1, 25);
                             QUERY PLAN
═════════════════════════════════════════════════════════════════════
 Function Scan on generate_series  (cost=0.00..0.25 rows=25 width=4)
(1 row)

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com

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