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From Erick Erickson <erickerick...@gmail.com>
Subject Re: Efficient filtering advise
Date Mon, 23 Nov 2009 12:55:39 GMT
Now I'm really confused, which usually means I'm making some
assumptions that aren't true. So here they are...

1> You're talking about Filters that contain BitSets, right? Not some other
     kind of filter.
2> When you create your 10-50K filters, you wind up with a single filter
     by combining them all with one of the BitSet operators, right? And
     that *single* filter is the one you send to your query...

If I'm off base here, could you post a reasonable extract of your filter
construction code, and how you use them to search? Because I don't
think we're all talking about the same thing here.....

HTH
Erick@ThisMakesNoSenseToMe<G>...

On Mon, Nov 23, 2009 at 5:18 AM, Eran Sevi <eransevi@gmail.com> wrote:

> After commenting out the collector logic, the time is still more or less
> the
> same.
> Anyway, since without the filter collecting the documents is very fast it's
> probably something with the filter itself.
>
> I don't know how the filter (or boolean query) work internally but probably
> for 10K or 50K clauses, it does something that takes a lot of time. It
> might
> be because of the inner data structures that are used or maybe just the
> iteration on so many terms takes time.
>
> I'll continue to try and pinpoint the exact bottleneck postion, or maybe
> using the new filters in 2.9.1 might help.
>
> On Sun, Nov 22, 2009 at 8:36 PM, Erick Erickson <erickerickson@gmail.com
> >wrote:
>
> > Hmmm, could you show us what you do in your collector? Because
> > one of the gotchas about a collector is loading the documents in
> > the inner loop. Quick test: comment out whatever you're doing in
> > the underlying collector loop, and see if there's *any* noticeable
> > difference in speed. That'll tell you whether your problems
> > arise from the filter construction/search or what you're doing
> > in the collector....
> >
> > Best
> > Erick
> >
> > On Sun, Nov 22, 2009 at 11:41 AM, Eran Sevi <eransevi@gmail.com> wrote:
> >
> > > I think it shouldn't take X5 times longer since the number of results
> is
> > > only about X2 times larger (and much smaller than the number of terms
> in
> > > the
> > > filter), but maybe I'm wrong here since I'm not familiar with the
> filter
> > > internals.
> > >
> > > Unfortunately, the time to construct the filter is mere milliseconds.
> > > almost all of the time (~5secs) are spent in the search method.
> > > I'm using a collector to retrieve all the results (and fetch a value
> for
> > > some fields) but without the filter this also takes less then a second
> > for
> > > the same number of results.
> > >
> > > On Sun, Nov 22, 2009 at 5:57 PM, Erick Erickson <
> erickerickson@gmail.com
> > > >wrote:
> > >
> > > > Hmmm, I'm not very clear here. Are you saying that you effectively
> > > > form 10-50K filters and OR them all together? That would be
> > > > consistent with the 50K case taking approx. 5X a long as the 10K
> > > > case.....
> > > >
> > > > Do you know where in your code the time is being spent? That'd
> > > > be a big help in suggesting alternatives. If I'm on the right track,
> > > > I'd expect the time to be spent assembling the filters.....
> > > >
> > > > Not much help here, but I'm having trouble wrapping my head
> > > > around this...
> > > >
> > > > Best
> > > > Erick
> > > >
> > > > On Sun, Nov 22, 2009 at 9:48 AM, Eran Sevi <eransevi@gmail.com>
> wrote:
> > > >
> > > > > Hi,
> > > > >
> > > > > I have a need to filter my queries using a rather large subset of
> > terms
> > > > > (can
> > > > > be 10K or even 50K).
> > > > > All these terms are sure to exist in the index so the number of
> > results
> > > > can
> > > > > be about the same number of terms in the filter.
> > > > > The terms are numbers but are not subsequent and are from a large
> set
> > > of
> > > > > possible values (so range queries are probably not good for me).
> > > > > The index itself is about 1M docs and running even a simple query
> > with
> > > > such
> > > > > a large filter takes a lot of time even if the number of results
is
> > > only
> > > > a
> > > > > few hundred docs.
> > > > > It seems like the speed is affected by the length of the filter
> even
> > if
> > > > the
> > > > > number of results remains more or less the same, which is logical
> but
> > > not
> > > > > by
> > > > > such a large loss of performance as I'm experiencing (running the
> > query
> > > > > with
> > > > > a 10K terms filter takes an average of 1s 187ms with 600 results
> > while
> > > > > running it with a 50K terms filter takes an average of 5s 207ms
> with
> > > 1000
> > > > > results).
> > > > >
> > > > > Currently I'm using a QueryFilter with a boolean query in which I
> > "OR"
> > > > the
> > > > > different terms together.
> > > > > I also can't use a cached filter efficiently since the terms to
> > filter
> > > on
> > > > > change almost every query.
> > > > >
> > > > > I was wondering if there's a better way to filter my queries so
> they
> > > > won't
> > > > > take a few seconds to run?
> > > > >
> > > > > Thanks in advance for any advise,
> > > > > Eran.
> > > > >
> > > >
> > >
> >
>

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