Proposal: collect frequency statistics for arrays

From: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
To: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Proposal: collect frequency statistics for arrays
Date: 2011-02-18 18:51:08
Message-ID: AANLkTikiruxOYh6jE_ETK7u4sEW6VXXqFK3Xn0-zVxoe@mail.gmail.com
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Hackers,

I have following proposal. Currently the ts_typanalyze function accumulates
frequency statistics for ts_vector using lossy counting technique. But no
frequency statistics is collecting over arrays. I'm going to generalize
ts_typanalyze to make it collecting statistics for arrays too. ts_typanalyze
internally uses lexeme comparison and hashing. I'm going to use functions
from default btree and hash opclasses of array element type in this
capacity. Collected frequency statistics for arrays can be used for && and
@> operators selectivity estimation.

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With best regards,
Alexander Korotkov.

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