Date: Thu, 26 Jan 2017 00:26:48 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: 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: <20170126032648.i2obutrun6k5bkle@alvherre.pgsql>
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Alvaro Herrera wrote:

> I wonder if heap_hot_search_buffer() and heap_hot_search() should return
> a tri-valued enum instead of boolean; that idea looks reasonable in
> theory but callers have to do more work afterwards, so maybe not.
> 
> I think heap_hot_search() sometimes leaving the buffer pinned is
> confusing.  Really, the whole idea of having heap_hot_search have a
> buffer output argument is an important API change that should be better
> thought.  Maybe it'd be better to return the buffer pinned always, and
> the caller is always in charge of unpinning if not InvalidBuffer.  Or
> perhaps we need a completely new function, given how different it is to
> the original?  If you tried to document in the comment above
> heap_hot_search how it works, you'd find that it's difficult to
> describe, which'd be an indicator that it's not well considered.

Even before your patch, heap_hot_search claims to have the same API as
heap_hot_search_buffer "except that caller does not provide the buffer."
But this is a lie and has been since 9.2 (more precisely, since commit
4da99ea4231e).  I think WARM makes things even worse and we should fix
that.  Not yet sure which direction to fix it ...

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


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