On Wed, Apr 27, 2022 at 09:44:21AM -0400, Tom Lane wrote: > =?koi8-r?B?8MHO1MDbyc4g4czFy9PBzsTSIOnXwc7P18ne?= <ai.pantyus...@gaz-is.ru> > writes: > > When I create a new table, and then I evaluate the execution of the SELECT > > query, I see a strange rows count in EXPLAIN > > CREATE TABLE test1(f INTEGER PRIMARY KEY NOT NULL); > > ANALYZE test1; > > EXPLAIN SELECT * FROM test1; > > QUERY PLAN > > --------------------------------------------------------- > > Seq Scan on test1 (cost=0.00..35.50 rows=2550 width=4) > > (1 row) > > > Table is empty but rows=2550. > > This is intentional, arising from the planner's unwillingness to > assume that a table is empty. It assumes that such a table actually > contains (from memory) 10 pages, and then backs into a rowcount > estimate from that depending on the data-type-dependent width of > the table rows. > > Without this provision, we'd produce very bad plans for cases > where a newly-populated table hasn't been analyzed yet.
We could have a noice mode that warns when a table without statistics is used. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Indecision is a decision. Inaction is an action. Mark Batterson
