Re: Question about Expected rows value in EXPLAIN output for Nested Loop node

Thanks for the reply. Here it is: https://explain.depesz.com/s/LQCS

My main trouble is not with this exact case, but i am looking for a general description of the algorithm how those numbers are calculated. In the meanwhile i also constructed a couple of artificial tables to experiment with and see how these numbers change, and am pretty sure my guesses there in the original question are quite close to what is going on, but would be so much easier to read explain plans, if there was some documentation about how the expected rows are calculated for different nodes, in different contexts (like when loops=1 vs loops>1) maybe what statistics they use, how they depend on the numbers of their child nodes etc.

>-------- Оригинално писмо --------

>От: Adrian Klaver adrian(dot)klaver(at)aklaver(dot)com

>Относно: Re: Question about Expected rows value in EXPLAIN output for Nested
Loop node

>До: bb ddd <nnickoloff1234(at)abv(dot)bg>

>Изпратено на: 10.05.2019 16:52

> On 5/10/19 5:32 AM, bb ddd wrote:

> >

> > Not sure why some of the new lines disappeared in the original message.

> > here is the part that got most corrupted with some more new lines lets

> > hope it looks more readable now

> >

> >

> >

> > 1) I have 2 Index Scans inside a Nested Loop

> >

> > 2) Nested Loop's expected rows=1268

> >

> >

> > 3.1) First Index Scan's expected rows=7

> >

> > 3.2) Second Index Scan's expected rows=43810

> >

>

> The best way to handle this is to post your EXPLAIN output to:

>

> https://explain.depesz.com/

>

> and then post the link here.

>

> --

> Adrian Klaver

> adrian(dot)klaver(at)aklaver(dot)com