Creation of the filters is very expense - usually involves a large
range query. We also convert all range and prefix queries to filters
since scoring these does not make sense to us...
For example, show sales where the sales price was > 0 and less than
500k. Frequently the user will get too many results, and so then he
will add another term (like the neighborhood).
Having the "sale price" filter cached helps performance immensely.
This is a bit of a contrived example (since sales are not updated
very frequently).
A better example comes from Nutch. In the query optimizer, terms with
a 0 boost that occur in N percent of the documents are converted into
a filter. Having to recreate his filter everytime a docment is added
is very expensive. With this change there is no performance hit to
using the filter optimzation with highly interactive indices.
On Jul 10, 2006, at 10:31 PM, Bruce Ritchie wrote:
Robert,
Can you quantify 'through the roof' a bit? Are the filters that you
are
creating that expensive to create or is it the usage of BitSets
that are
the real cause of the performance improvement you've seen?
Regards,
Bruce Ritchie
-----Original Message-----
From: robert engels [mailto:[EMAIL PROTECTED]
Sent: Friday, July 07, 2006 9:35 PM
To: java-dev@lucene.apache.org
Subject: Re: MultiSegmentQueryFilter enhancement for interactive
indexes?
I implemented it and it works great. I didn't worry about the
deletions
since by the time a filter is used the deleted documents are already
removed by the query. The only problem that arose out of this was for
things like the ConstantScoreQuery (which uses a filter)
- I needed to modify this query to ignore deleted documents.
Now I have incremental cached filters - the query performance is going
through the roof.
On Jul 7, 2006, at 2:47 PM, Chris Hostetter wrote:
I'm no segments/MultiReader expert, but your idea sounds good to me
... it seems like it would certainly work in the "new segments"
situation.
One thing i don't see you mention is dealing with deletions ... i'm
not sure if deleting documents cause the version number of an
IndexReader to change or not (if it does your job is easy) but
even if
it doesn't I'm guessing you could say that if hasDeletions() returns
true, you have to assume you need to invalidate your cached bits
(worst case scenerio you are invalidating the cache as often as it is
now)
: Date: Fri, 7 Jul 2006 00:32:54 -0500
: From: robert engels <[EMAIL PROTECTED]>
: Reply-To: java-dev@lucene.apache.org
: To: Lucene-Dev <java-dev@lucene.apache.org>
: Subject: MultiSegmentQueryFilter enhancement for interactive
indexes?
:
: I thought of a possible enhancement - before I go down the road, I
am
: looking for some input form the community?
:
: Currently, the QueryFilter caches the bits base upon the
IndexReader.
:
: The problem with this is small incremental changes to the index
: invalidate the cache.
:
: What if instead the filter determined that the underlying
IndexReader
: was a MultiReader and then maintained a bitset for each reader,
: combining them in bits() when requested. The filter could check if
: any of the underlying readers were the different (removed or added)
: and then just create a new bitset for that reader. With the new
non-
: bit set filter implementations this could be even more memory
: efficient since the bitsets would not need to be combined into a
: single bitset.
:
: With the previous work on "reopen" so that segments are reused,
this
: would allow filters to be far more useful in a highly interactive
: environment.
:
: What do you think?
:
:
:
:
:
:
:
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-Hoss
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