Re: update statistics not recommended!
On Fri, 14 Aug 1998 17:48:36 +0100, in article <35D46A64.2BFB@netcomuk.co.uk>,
Neil Truby <ntruby@netcomuk.co.uk> wrote:
>My new site has a third-party financial package (Lawsons), running on
>v7.13. The underlying DBMS is Informix. The Lawsons help desk has told
>me that they recommend that we never run UPDATE STATISTICS, as it will
>degrade performance. Their reasoning, allegedly based on empirical
>evidence of their users, is that all their SQL is written with where
>clauses, and the indexes that exist will be used, which is what is
>required. If we run an UPDATE STATS, we might risk unexpected and
>undesirable access paths. A caveat is added that, under v7.23, some
>customers have experienced benefits from an UPDATE STATISTICS LOW, and
>that we might run it, but prepared to remove the statistics so derived
>if performance nose-dives.
>
>Well, sounds like bollocks to me, but does anyone else have any views
>or, better still, experience of this software packeage running with
>Informix?
Bullocks is puting it mildly. Updates statistics HIGH on primary key indexes
and update statistics low on the tables will improve database performance.
Perhaps they want to blame problems with the way their software is written on
update statistics but that's just not so. 4gl doesn't tell the database whichindex to use, but badly written code can indeed use the indexes wrong if for
example, they do a select from a, b where and a has FEWER rows than b. But
again, that's not going to change with update statistics. Bad code is bad
code.
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