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Re: Common Table Expressions (WITH RECURSIVE) patch

From: "Hitoshi Harada" <umi(dot)tanuki(at)gmail(dot)com>
To: "Dimitri Fontaine" <dfontaine(at)hi-media(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Greg Stark" <greg(dot)stark(at)enterprisedb(dot)com>, "Jeff Davis" <pgsql(at)j-davis(dot)com>, "Tatsuo Ishii" <ishii(at)postgresql(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Common Table Expressions (WITH RECURSIVE) patch
Date: 2008-10-01 00:59:37
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Lists: pgsql-hackers

2008/10/1 Dimitri Fontaine <dfontaine(at)hi-media(dot)com>:
> Hash: SHA1
> Hi,
> Le 30 sept. 08 à 20:03, Tom Lane a écrit :
>>        set_read_position(tupstore, &local_read_position);
>>        tuple = tuplestore_gettuple(tupstore, ...);
>>        get_read_position(tupstore, &local_read_position);
>> rather than just tuplestore_gettuple.  The set/get functions will be
>> cheap enough that this is no big deal.  (Or maybe we should just
>> provide a wrapper function that does this sequence?)
> It seems to me to share some ideas with the MemoryContext concept: what
> about a TupstoreContext associated with tuplestore, you get a common default
> one if you don't register your own, and use
>        tuplestore_gettuple(MyTupstoreContext, ...);
> Maybe some other API would benefit from the idea?

I'm just working on tuplestore recording multiple positions for my
window function project. Attached patch is still in progress but seems
it works in a situation.

From my work, the setting/getting read position and delegate savig
positions to the caller will probably have problems, because of memory
control for saving positions and tuplestore status changing (memory ->
BufFile). Instead, I decided it'd better that we can indicate the row
number by integer.


Hitoshi Harada

Attachment: tuplestore.c.diff
Description: text/x-patch (6.3 KB)

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