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From "Earwin Burrfoot (JIRA)" <>
Subject [jira] Commented: (LUCENE-1461) Cached filter for a single term field
Date Wed, 26 Nov 2008 07:28:44 GMT


Earwin Burrfoot commented on LUCENE-1461:

Somewhat off topic, but nonetheless, my two techniques for superfast range queries/filters:
1. cache [from, null]+[null, to] filters instead of [from, to] and intersect them
-> can tremendously improve cache hits for certain setups

2. when indexing a field that will be used for range filter, index lower-resolution versions
of it additionally, than use a union of rangefilters over different resolution fields, ie:
a. we have severalM documents with a date field spanning few years with say minute precision
(we'd like to sort on it afterward)
b. we index additional fields with dates rounded down to something like years, months, days,
hours (best combination depends on width of the queries you're most likely to perform, let's
say it's day+hour for queries rarely spanning more than a month)
c. we have a query like [2008-05-05 18:00 .. 2008-06-01 10:53], it is converted to -> hour:[05-05
18 .. 05-06 00) or day:[05-06 .. 06-01) or hour:[06-01 00 .. 06-01 10) or minute:[06-01 10:00
.. 06-01 10:53]
-> massive win for ranges over fields having lots of high-selectivity terms, with timestamps
being a good example, also salaries, coordinates, whatever

> Cached filter for a single term field
> -------------------------------------
>                 Key: LUCENE-1461
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>            Reporter: Tim Sturge
>         Attachments:, LUCENE-1461a.patch, LUCENE-1461b.patch,,,
> These classes implement inexpensive range filtering over a field containing a single
term. They do this by building an integer array of term numbers (storing the term->number
mapping in a TreeMap) and then implementing a fast integer comparison based DocSetIdIterator.
> This code is currently being used to do age range filtering, but could also be used to
do other date filtering or in any application where there need to be multiple filters based
on the same single term field. I have an untested implementation of single term filtering
and have considered but not yet implemented term set filtering (useful for location based
searches) as well. 
> The code here is fairly rough; it works but lacks javadocs and toString() and hashCode()
methods etc. I'm posting it here to discover if there is other interest in this feature; I
don't mind fixing it up but would hate to go to the effort if it's not going to make it into

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