Re: Understanding bad estimate (related to FKs?)

Philip Semanchuk <philip@americanefficient.com> writes:
> The query I asked about in the original post of this thread has 13 relations in it. IIUC, that's 13! or > 6 billion
possibleplans. How did the planner pick one plan out of 6 billion? I'm curious, both for practical purposes (I want my
queryto run well) and also because it's fascinating. 

The twenty-thousand-foot overview is

https://www.postgresql.org/docs/devel/planner-optimizer.html

and then ten-thousand-foot level is the planner README file,

https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob_plain;f=src/backend/optimizer/README;hb=HEAD

and then you pretty much gotta start reading code.  You could also dig
into various planner expository talks that people have given at PG
conferences.  I don't have links at hand, but there have been several.

            regards, tom lane