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Odd performance problem with substring index
I have an odd problem with OpenLDAP 2.0.7 that I'd like some input on.
I'm setting up a catalog with approximately a million nodes in it. My
problem is that the performance of a substring index seems half arbitrary,
dependent on where in the search string I put globs (*) -- _sometimes_
OpenLDAP seems to do a linear search, even though the attribute searched on
To be more concrete, the relevant part of my catalog structure is like
- uid: foo
- mail: firstname.lastname@example.org
Now, I have eq and sub indexes on the mail attribute, so I expect the
following searches to return the correct result pretty quickly:
My observation is that only searches 1 and 2 respond quickly (<0.1sec),
while the others use several minutes, pretty much the same time as a search
on a non-indexed attribute.
However, if I add another glob to searches 5-7, I can get better
performance. The following perform quickly:
...while the following are very slow:
Is it a known issue? If so: is there a general work-around I can rely on?
Apart from this issue, I'm happy with the performance of OpenLDAP with a
million nodes. Even the write performance, with a couple of indexes and
with the database files on a RAID5 volume, is pretty good.