From: =?UTF-8?Q?J=c3=bcrgen_Purtz?= <juergen@purtz.de>
Subject: Re: obsolete indexing method "rtree"
To: pgsql-docs@lists.postgresql.org
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 <2510904.1596636088@sss.pgh.pa.us>
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Date: Thu, 6 Aug 2020 09:18:35 +0200
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> Why?

Because it can hinder the learning process. And it's possible that 
people ignore or forget about the warning message, but are confused 
somewhat later that commands like \d shows GiST instead of RTREE.

> It's not hurting anything to continue the substitution in CREATE
> INDEX.
Yes, it's not hurting. But it makes the life of newcomers a little 
harder. Why not stripping away thinks which aren't used since 12 years?
> Possibly the comment in seg.sgml should be adjusted to refer to GiST
> indexes --- but then again, it's not entirely clear whether it's even
> still relevant for GiST indexes.
This comment is not specific to the old rtree implementation. In 
general, the input to R-Trees and the algorithm which creates the 
'rectangles' in non-leaf nodes influences the building of the tree and 
hereinafter the performance of access methods.
> Perhaps it's talking about a deficiency
> that was specific to the old rtree code.

And sometimes even experts have to spend time thinking about the situation.

Nevertheless, this is a tiny issue. Unfortunately I don't have the 
knowledge to modify the C-source and create a patch.

--

Jürgen Purtz