Re: Sort returns more rows than seq scan?

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Sort returns more rows than seq scan?
Date: 2016-03-01 14:52:26
Message-ID: CAFj8pRBdYQMUeDoxBGN9=84zjdDJDp9wfZdCo_=_04z6MPWTAQ@mail.gmail.com
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2016-03-01 15:45 GMT+01:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> 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
>

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