Re: [HACKERS] problem when optimizing the window aggregation

[Wang, Chaoyong]

Thanks again, the reason is found.

The following statement frees all the context for aggregation, including the 
transValue and tempTransValue:
  MemoryContextResetAndDeleteChildren(winstate->aggcontext);


-Original Message-
From: Tom Lane [mailto:t...@sss.pgh.pa.us] 
Sent: 2012年8月22日 9:47
To: Wang, Chaoyong
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] problem when optimizing the window aggregation

"Wang, Chaoyong"  writes:
> I used the function datumCopy as following:

> peraggstate->transValue = datumCopy(peraggstate->tempTransValue,
> peraggstate->transtypeByVal, peraggstate->transtypeLen);

You need to guard that with an is-null check, because datumCopy isn't
designed to cope with null values.  (Which is historical, I guess, but
we're not likely to change it now.)  If you look around you will find
plenty of examples of this coding pattern.

regards, tom lane



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Re: [HACKERS] problem when optimizing the window aggregation

[Tom Lane]

"Wang, Chaoyong"  writes:
> I used the function datumCopy as following:

> peraggstate->transValue = datumCopy(peraggstate->tempTransValue,
> peraggstate->transtypeByVal, peraggstate->transtypeLen);

You need to guard that with an is-null check, because datumCopy isn't
designed to cope with null values.  (Which is historical, I guess, but
we're not likely to change it now.)  If you look around you will find
plenty of examples of this coding pattern.

regards, tom lane


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[HACKERS] problem when optimizing the window aggregation

[Wang, Chaoyong]

Hi,

 

I'm trying to reduce the re-computing of window aggregation. Here the
AVG function for example.

 

The original window aggregation's transition value(transValue) of AVG is
an ArrayType, that contains two main values(sum, count). 

 

Now, I'm using a temporary transition value (tempTransValue), and I need
to copy tempTransValue to transValue.

 

I used the function datumCopy as following:

peraggstate->transValue = datumCopy(peraggstate->tempTransValue,
peraggstate->transtypeByVal, peraggstate->transtypeLen);

 

But when the copied transValue is passed to the invoke function, here is
int4_avg_accum, the ArrayType returned from PG_GETARG_ARRAYTYPE_P(0) is
null.

Which means the copy action is failed.

 

Anybody know why? Or give me some suggestions? Thanks very much.

 

 

Best Regards

Chaoyong Wang