Re: [HACKERS] Sort returns more rows than seq scan?

2016-03-01 Thread Pavel Stehule 
2016-03-01 15:45 GMT+01:00 Tom Lane :

> Pavel Stehule  writes:
> > I don't understand how is possible to get more rows from Sort node than
> in
> > nested seq scan?
>
> The "extra" rows are re-fetches triggered by mark/restore requests from
> the parent mergejoin.  The EXPLAIN instrumentation counts re-fetches as
> if they were new rows.
>

aha,

Thank you for explain

Regards

Pavel


>
> regards, tom lane
>

Re: [HACKERS] Sort returns more rows than seq scan?

2016-03-01 Thread Tom Lane 
Pavel Stehule  writes:
> I don't understand how is possible to get more rows from Sort node than in
> nested seq scan?

The "extra" rows are re-fetches triggered by mark/restore requests from
the parent mergejoin.  The EXPLAIN instrumentation counts re-fetches as
if they were new rows.

regards, tom lane


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers