Re: slow queries with long strings in filters

[Andreas Hasenack <ahasenack@terra.com.br>]

On Thu, Nov 09, 2006 at 03:34:38PM +0100, 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 substring index is not generated for long strings. Check these in
slapd.conf(5):
index_substr_if_minlen <integer>
index_substr_if_maxlen <integer>
index_substr_any_len <integer>
index_substr_any_step <integer>

In the end, you may be better off spliting that big string in
multivalued attributes perhaps or somethine else.

> Using subinitial or subany in the index slap.conf parameter did not
> solve the problem.
> 
> 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)

Defaults may have changed. In earlier versions, this was a compile time
definition.