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Re: BUG #2196: Useless RECHECK on RTREE index

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "" <agattik(at)gmail(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #2196: Useless RECHECK on RTREE index
Date: 2006-01-23 17:26:04
Message-ID: 6743.1138037164@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
"" <agattik(at)gmail(dot)com> writes:
>  Bitmap Heap Scan on tpoints  (cost=1.05..10.46 rows=10 width=8)
>    Recheck Cond: ('(1,1),(0,0)'::box && box(point((x)::double precision,
> (y)::double precision), point((x)::double precision, (y)::double
> precision)))
>    ->  Bitmap Index Scan on i_tpoints  (cost=0.00..1.05 rows=10 width=0)
>          Index Cond: ('(1,1),(0,0)'::box && box(point((x)::double precision,
> (y)::double precision), point((x)::double precision, (y)::double
> precision)))
> (4 rows)

> The RECHECK is necessary in case of polygons, but useless in case of box
> overlap.

You don't understand what a bitmap scan's recheck condition is for.
The above plan is correct.

			regards, tom lane

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