Horton

Re: Proposal: Improve bitmap costing for lossy pages

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Alexander Kumenkov <a.kuzmenkov@postgrespro.ru>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-10-05T14:45:52Z
Lists: pgsql-hackers 
On Sun, Sep 17, 2017 at 7:04 AM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> I used  lossy_pages = max(0, total_pages - maxentries / 2). as
> suggesed by Alexander.

Does that formula accurately estimate the number of lossy pages?

The performance results look good, but that's a slightly different
thing from whether the estimate is accurate.

+    nbuckets = tbm_calculate_entires(maxbytes);

entires?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Account for the effect of lossy pages when costing bitmap scans.