Re: index fragmentation on insert-only table with non-unique column

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Claudio Freire <klaussfreire(at)gmail(dot)com>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: index fragmentation on insert-only table with non-unique column
Date: 2016-06-05 16:03:58
Message-ID: 969.1465142638@sss.pgh.pa.us
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Claudio Freire <klaussfreire(at)gmail(dot)com> writes:
> So correlated index scans look extra favourable vs bitmap index scans
> because bitmap heap scans consider random page costs sans correlation
> effects (even though correlation applies to bitmap heap scans as
> well).

Really? How? The index ordering has nothing to do with the order in
which heap tuples will be visited.

regards, tom lane

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