From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Deferring some AtStart* allocations? |
Date: | 2014-06-30 00:19:31 |
Message-ID: | 20140630001931.GH21422@awork2.anarazel.de |
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Lists: | pgsql-hackers |
On 2014-06-29 19:52:23 -0400, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > Why aren't we delaying allocations in e.g. AtStart_Inval(),
> > AfterTriggerBeginXact() to when the data structures are acutally used?
>
> Aren't we? Neither of those would be doing much work certainly.
They are perhaps not doing much in absolute terms, but it's a fair share
of the processing overhead for simple statements. AfterTriggerBeginXact()
is called unconditionally from StartTransaction() and does three
MemoryContextAlloc()s. AtStart_Inval() one.
I think they should just be initialized whenever the memory is used?
Doesn't look too complicated to me.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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