Re: Polyphase Merge

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From: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Sent: Monday, January 21, 2008 10:13 PM
To: "Sam Mason" <sam(at)samason(dot)me(dot)uk>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] Polyphase Merge

>
> I agree --- having to read the run back from external storage, only to
> write it out again with no further useful work done on it, sounds like
> a guaranteed loser. To make this work you'll need some kind of ju-jitsu
> rearrangement that logically puts the run where it needs to go without
> physically moving any data.

I'm not going to write it back with no useful work on it. I should just
write them in reverse order during run formation (ju-jitsu couldn't help me
in this case) or read them in reverse order while merging (ju-jitsu may
help... the point is that I'm not so good in ju-jitsu).

An idea could be managing a list of pointers to runs contained into tapes.
Any comment?

> regards, tom lane
>
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