Filter Query, Filter Cache and Hit Ratio

[Renaud Delbru]

Hi,

I am looking for some more information on how the filter cache is 
working, and how the hit are incremented.

We are using filter queries for certain predefined value, such as the 
timestamp:[2011-01-21T00:00:00Z+TO+NOW] (which is the current day). From 
what I understand from the documentation:
"the filter cache stores the results of any filter queries ("fq" 
parameters) that Solr is explicitly asked to execute. (Each filter is 
executed and cached separately. When it's time to use them to limit the 
number of results returned by a query, this is done using set 
intersections.)"
So, we were imagining that is two consecutive queries (as the one above) 
was using the same timestamp filter query, the second query will take 
advantage of the filter cache, and we would see the number of hits 
increasing (hit on the cached timestamp filter query) . However, this is 
not the case, the number of hits on the filter cache does not increase 
and stays very low. Is it normal ?

INFO: [] webapp=/siren path=/select 
params={wt=javabin&rows=0&version=2&fl=id,score&start=0&q=*:*&isShard=true&fq=timestamp:[2011-01-21T00:00:00Z+TO+NOW]&fq=domain:my.wordpress.com&fsv=true} 
hits=0 status=0 QTime=139
INFO: [] webapp=/siren path=/select 
params={wt=javabin&rows=0&version=2&fl=id,score&start=0&q=*:*&isShard=true&fq=timestamp:[2011-01-21T00:00:00Z+TO+NOW]&fq=domain:syours.wordpress.com&fsv=true} 
hits=0 status=0 QTime=138

--
Renaud Delbru