Date: Thu, 15 Oct 2015 23:13:35 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: zhangjinyu <beijing_pg@163.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Patch: Optimize memory allocation in function
 'bringetbitmap'
Message-ID: <20151016021334.GA3391@alvherre.pgsql>
References: <495deb78.4186.1500dacaa63.Coremail.beijing_pg@163.com>
 <20150927175608.GM295765@alvherre.pgsql>
 <1443451254826-5867647.post@n5.nabble.com>
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zhangjinyu wrote:

> >>>>However I wonder if it would be simpler to have the dtup structure have
> >>>>the pointers, so that you can pass it as NULL in the first call and then
> >>>>followup calls reuse the one allocated in the first call.
> Jinyu:  the memory is allocated from perRangeCxt  and perRangeCxt will be
> reset in loop,
> so this way don't work. 

You're right.  I think we can do better: have brin_deform_tuple accept
another argument of type BrinMemTuple *, which can be NULL.  If NULL,
the function calls brin_new_memtuple to allocate a new one (just like
current code); if not NULL, that one is used.  Have brin_new_memtuple
also allocate the values/allnulls/hasnulls arrays, which are now part of
the BrinMemTuple struct.  Then, bringetbitmap calls brin_new_memtuple
once before changing to perRangeCxt, then reuse the returned inside the
loop (we probably need brin_memtuple_initialize to clear out the struct
at the end of each loop iteration).  Other callers of brin_deform_tuple
just pass NULL to get the current behavior.

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


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