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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Ron <rjpeace@earthlink.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: [GENERAL] Creation of tsearch2 index is very
Date: Sat, 21 Jan 2006 13:27:53 -0500
Message-ID: <18771.1137868073@sss.pgh.pa.us> (raw)
In-Reply-To: <7.0.1.0.2.20060121064930.03aba810@earthlink.net>
References: <26153.1137784469@sss.pgh.pa.us>
	<20060120201036.GE31908@svana.org>
	<26583.1137788505@sss.pgh.pa.us>
	<20060120205132.GF31908@svana.org>
	<26958.1137791955@sss.pgh.pa.us>
	<20060120213754.GG31908@svana.org>
	<7.0.1.0.2.20060120174141.039b03e8@earthlink.net>
	<6111.1137797436@sss.pgh.pa.us>
	<20060120225751.GA27230@uio.no>
	<6532.1137801157@sss.pgh.pa.us>
	<20060121000519.GA29755@uio.no>
	<6743.1137802990@sss.pgh.pa.us>
	<7.0.1.0.2.20060121064930.03aba810@earthlink.net>

Ron <rjpeace@earthlink.net> writes:
> At 07:23 PM 1/20/2006, Tom Lane wrote:
>> Well, we're trying to split an index page that's gotten full into 
>> two index pages, preferably with approximately equal numbers of items in
>> each new page (this isn't a hard requirement though).

> Maybe we are over thinking this.  What happens if we do the obvious 
> and just make a new page and move the "last" n/2 items on the full 
> page to the new page?

Search performance will go to hell in a handbasket :-(.  We have to make
at least some effort to split the page in a way that will allow searches
to visit only one of the two child pages rather than both.

It's certainly true though that finding the furthest pair is not a
necessary component of that.  It's reasonable if you try to visualize
the problem in 2D or 3D, but I'm not sure that that geometric intuition
holds up in such a high-dimensional space as we have here.

			regards, tom lane



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