Does {Filter}ing is faster than {Query}ing in Lucene?

[Denis Bazhenov <do...@gmail.com>]

While reading "Lucene in Action 2nd edition" I came across the description of Filter classes which are could be used for result filtering in Lucene. Lucene has a lot of filters repeating Query classes. For example, NumericRangeQuery and NumericRangeFilter.

The book says that NRF does exactly the same as NRQ but without document scoring. Does this means that if I do not need scoring or sort documents by document field value I should preferFiltering over Querying from performance point of view?

---
Denis Bazhenov <do...@gmail.com>

RE: Does {Filter}ing is faster than {Query}ing in Lucene?

[Uwe Schindler <uw...@thetaphi.de>]

Hi,

If you dont cache filters, queries will be faster, as the ConjunctionScorer
in Lucene has optimizations, which are currently not used for Filters.
Filters are fine, if you cache them (e.g. if you always have the same access
restrictions for a specific user that are applied to all his queries). In
that case the Filter is only executed once and cached for all further
requests and then intersected with the query result set.

If you only want to e.g. randomly "filter" e.g. by a variable numeric range
like a bounding box in a geographic search, use queries, queries are in most
cases faster (e.g. Range Queries and similar stuff - called MultiTermQueries
- are internally also implemented by the same BitSet algorithm like the
Filter - in fact they are only Filters wrapped by a Scorer-impl). But the
Scorer that ANDs the query and your "filter" query together
(ConjunctionScorer) is generally faster than the code that applies the
filter after searching. This may some improvement possible, but in general
filters are something in Lucene that is not really needed anymore, so there
were already some approaches to make Filters and Queries the same, and
instead then be able to also cache non-scoring queries. This would make lots
of code easier.

Filters can bring a huge speed improvement with  Lucene 4.0, if they are
plugged ontop of the IndexReader to filter the documents *before* scoring,
but that's not yet implemented (see
https://issues.apache.org/jira/browse/LUCENE-3212) - I am working on it. We
may also make Filters random access (it's easy as they are bitsets), which
could improve also the after-query filtering. But I would then also make
Queries partially random access, if they could support it (like queries that
are only based on FieldCache).

Uwe

-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de


> -----Original Message-----
> From: Denis Bazhenov [mailto:dotsid@gmail.com]
> Sent: Friday, June 24, 2011 3:21 AM
> To: java-user@lucene.apache.org
> Subject: Does {Filter}ing is faster than {Query}ing in Lucene?
> 
> While reading "Lucene in Action 2nd edition" I came across the description
of
> Filter classes which are could be used for result filtering in Lucene.
Lucene
> has a lot of filters repeating Query classes. For example,
NumericRangeQuery
> and NumericRangeFilter.
> 
> The book says that NRF does exactly the same as NRQ but without document
> scoring. Does this means that if I do not need scoring or sort documents
by
> document field value I should preferFiltering over Querying from
> performance point of view?
> 
> ---
> Denis Bazhenov <do...@gmail.com>
> 
> 
> 
> 



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Re: Does {Filter}ing is faster than {Query}ing in Lucene?

[Ian Lea <ia...@gmail.com>]

Generalisation is risky, particularly wrt performance, but I'd say
yes, particularly if you can cache and reuse the filter e.g. with
CachingWrapperFilter.  See
http://wiki.apache.org/lucene-java/FilteringOptions.  Not very up to
date but I'd expect the conclusions to stand.


--
Ian.


On Fri, Jun 24, 2011 at 2:20 AM, Denis Bazhenov <do...@gmail.com> wrote:
> While reading "Lucene in Action 2nd edition" I came across the description of Filter classes which are could be used for result filtering in Lucene. Lucene has a lot of filters repeating Query classes. For example, NumericRangeQuery and NumericRangeFilter.
>
> The book says that NRF does exactly the same as NRQ but without document scoring. Does this means that if I do not need scoring or sort documents by document field value I should preferFiltering over Querying from performance point of view?
>
> ---
> Denis Bazhenov <do...@gmail.com>
>
>
>
>
>
>

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