Date: Tue, 14 Mar 2017 14:17:29 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Bruce Momjian <bruce@momjian.us>,
	Jaime Casanova <jaime.casanova@2ndquadrant.com>,
	Haribabu Kommi <kommi.haribabu@gmail.com>,
	Tomas Vondra <tomas.vondra@2ndquadrant.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Patch: Write Amplification Reduction Method (WARM)
Message-ID: <20170314171729.uxca6t3pjb3xiwed@alvherre.pgsql>
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After looking at how index_fetch_heap and heap_hot_search_buffer
interact, I can't say I'm in love with the idea.  I started thinking
that we should not have index_fetch_heap release the buffer lock only to
re-acquire it five lines later, so it should keep the buffer lock, do
the recheck and only release it afterwards (I realize that this means
there'd be need for two additional "else release buffer lock" branches);
but then this got me thinking that perhaps it would be better to have
another routine that does both call heap_hot_search_buffer and then call
recheck -- it occurs to me that what we're doing here is essentially
heap_warm_search_buffer.

Does that make sense?

Another thing is BuildIndexInfo being called over and over for each
recheck().  Surely we need to cache the indexinfo for each indexscan.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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