From: Claudio Sacerdoti Coen <claudio.sacerdoticoen@unibo.it>
Date: Mon, 29 Aug 2005 11:50:18 +0000 (+0000)
Subject: WARNING: this commit changes the DB representation; you need to alter the
X-Git-Tag: working_equations_only~13
X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;ds=inline;h=99f483320bd7b88af4f7e3a885054acb43dc22f0;hp=99f483320bd7b88af4f7e3a885054acb43dc22f0;p=helm.git

WARNING: this commit changes the DB representation; you need to alter the
         DB by hand after this commit

- h_position: varchar(255) -> varchar(62)
- h_sort:     varchar(255) -> varchar(6)
- several indexes have been redesigned from scratch.
  Motivation: MySql is not able to exploit two indexes (on columns c1 and c2)
  in a query of type "select ... from table where c1 = x and c2 = y".
  Only one of the two indexes is exploited; the other test is done on each line.  My commit introduces a single index on c1 AND c2 in place of two indexes.

WARNING: it is sure that a few queries (e.g. match) are greatly optimized by
this commit. On the contrary I ignore if the performance of other queries drops.Moreover, I have not optimized yet the indexes over the hits and count tables.
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