Re: Deferring some AtStart* allocations?

On 2014-06-29 19:52:23 -0400, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.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 &
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