Add to optimizer file.

doc/TODO.detail/optimizer

@@ -1059,7 +1059,7 @@ From owner-pgsql-hackers@hub.org Thu Jan 20 18:45:32 2000
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@@ -1837,3 +1837,86 @@ what's left.  I forget the figures exactly.
 
 Jules
 
+From pgsql-hackers-owner+M6154@hub.org Wed Aug 23 14:36:41 2000
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+Date: Wed, 23 Aug 2000 18:22:40 +0100 (WEST)
+From: =?iso-8859-1?Q?Tiago_Ant=E3o?= <tra@fct.unl.pt>
+X-Sender: tiago@eros.si.fct.unl.pt
+To: Tom Lane <tgl@sss.pgh.pa.us>
+cc: =?iso-8859-1?Q?Tiago_Ant=E3o?= <tra@fct.unl.pt>,
+        PostgreSQL Hackers list <pgsql-hackers@hub.org>
+Subject: Re: [HACKERS] analyze.c 
+In-Reply-To: <28154.967041988@sss.pgh.pa.us>
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+Status: ORr
+
+
+
+On Wed, 23 Aug 2000, Tom Lane wrote:
+
+> > What's the big reason not to do that? I know that
+> > there is some code in analyze.c (like comparing) that uses other parts of
+> > pg, but that seems to be easily fixed.
+> 
+> Are you proposing not to do any comparisons?  It will be interesting to
+> see how you can compute a histogram without any idea of equality or
+> ordering.  But if you want that, then you still need the function-call
+> manager as well as the type-specific comparison routines for every
+> datatype that you might be asked to operate on (don't forget
+> user-defined types here).
+
+   I forgot user defined data types :-(, but regarding histograms I think
+the code can be made external (at least for testing purposes):
+   1. I was not suggesting not to do any comparisons, but I think the only
+comparison I need is equality, I don't need order as I don't need to
+calculate mins or maxs (I just need mins and maxes on frequencies, NOT on 
+dat itself) to make a histogram.
+   2. The mapping to text guarantees that I have (PQgetvalue returns
+always char* and pg_statistics keeps a "text" anyway) a way of knowing
+about equality regardless of type.
+
+   But at least anything relating to order has to be in.
+
+> >   I'm leaning toward the implementation of end-biased histograms. There is
+> > an introductory reference in the IEEE Data Engineering Bulletin, september
+> > 1995 (available on microsoft research site).
+> 
+> Sounds interesting.  Can you give us an exact URL?
+
+http://www.research.microsoft.com/research/db/debull/default.htm
+
+BTW, you can get access to SIGMOD CDs with lots of goodies for a very low
+price (at least in 1999 it was a bargain), check out ACM membership for
+sigmod.
+
+I've been reading something about implementation of histograms, and,
+AFAIK, in practice histograms is just a cool name for no more than:
+   1. top ten with frequency for each
+   2. the same for top ten worse
+   3. average for the rest
+
+I'm writing code get this info (outside pg for now - for testing
+purposes).
+
+Best Regards,
+Tiago
+PS - again: I'm starting, so, some of my comments can be completly dumb.
+
+