Re: slow queries with long strings in filters
Sylvain Amrani wrote:
Hi list,
I've got an attribute that could contains very long strings (more than
150 chr).
It's a string made of small tokens separated by spaces and slashes :
departmentUID: BA/BAC ANDL/BAPZ IDF/GRPT YVLN/CIE GN ST GERM...
The attibute is indexed with pres,eq,sub
When I search for small substrings like (departmentUID=*/GRPT*) it's
fast and ok.
When I search for a long subset of the string, the query is _very_ long
(many seconds) :
(departmentUID=BA/BAC ANDL/BAPZ IDF/GRPT YVLN/CIE GN ST*)
The more the string is long, the more the answer is slow.
I can use very complex filters (&((|()())(|()()))... and the answer is
very fast, unless I use a long string in it.
The backend is BDB (berkeley 4.2)
Openldap is 2.2.26
Is this a BDB or an Openldap related issue ?
Using subinitial or subany in the index slap.conf parameter did not
solve the problem.
That's a feature of OpenLDAP in 2.2 and older; subinitial and subfinal
queries only index up to 4 characters of the string you provide. The
rest are ignored. So indexing is not narrowing down the search
candidates very much, and the full filter has to get evaluated on a lot
of extraneous entries.
You should upgrade to the current 2.3, which uses the entire input
string on index lookups.
I found only one post in the archives related to a server were any
query
string with more than 3 characters makes slow answers. He was told to
adjust :
index_substr_if_minlen
index_substr_if_maxlen
index_substr_any_len
index_substr_any_step
But theses parameters are only available with openldap 2.3 and it
doesn't seem to be exactly my problem (I've no differences between 2,3,4
or 5 characters query strings)
Thanks,
Sylvain.
--
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
OpenLDAP Core Team http://www.openldap.org/project/