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Re: reqStart<= slow

Howard Chu wrote:
> Michael StrÃder wrote:
>> HI!
>> I'm trying to retrieve change events from accesslog DB (all with today's
>> RE24). I tried searching with this filter:
>> (&(reqDN=cn=Test-Mail-Gruppe 1,dc=example,dc=com)(reqStart<=20120413180000Z))
>> This turned out to be quite slow though. reqDN is indexed and there are only
>> two possible entries. Using a filter reqStart>= even when negated with (!())
>> is pretty fast.
> Is reqStart indexed?

Yes, eq-indexed of course.

>> I really wonder why that is.
> Obviously, for any database that has been around for even a short while, there
> will be far fewer records with a date newer than [today's date] as opposed to
> older than then.

But there were only three entries matching
(reqDN=cn=Test-Mail-Gruppe 1,dc=example,dc=com)
anyway and reqDN is also eq-indexed and finding them with this filter is
pretty fast.

Some more examples where reqDN-index is obviously not used but reqStart-index
should be used in both cases:

Quite fast although I would have expected an significant slow down because of
negation filter:

Almost identical but very slow compared to the example above:

I can't explain this based on index configuration. Maybe there's something
handled differently with <= compared to >=?

Ciao, Michael.

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