Re: Row estimates for empty tables

> On Jul 24, 2020, at 06:48, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 
> There's certainly not a lot besides tradition to justify the exact
> numbers used in this case. 

Since we already special-case parent tables for partition sets, would a storage parameter that lets you either tell the planner "no, really, zero is reasonable here" or sets a minimum number of rows to plan for be reasonable?  I happened to get bit by this tracking down an issue where several tables in a large query had zero rows, and the planner's assumption of a few pages worth caused some sub-optimal plans.  The performance hit wasn't huge, but they were being joined to some *very* large tables, and the differences added up.
--
-- Christophe Pettus
   xof@thebuild.com