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https://issues.apache.org/jira/browse/LUCENE-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12851809#action_12851809
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Michael McCandless commented on LUCENE-1990:
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Toke, are sort ords that much slower than straight arrays for sorting?
After flex lands I'd really like to make a variant of FieldCache.StringIndex
that uses BytesRef for the values and packed ints for the ords.... should save
alot of memory in many cases (English text saves since utf8 is 1 byte per char;
enumerated fields (eg country name) should save tons by using only a few bits
instead of 32 we now always use) when sorting by string.
> Add unsigned packed int impls in oal.util
> -----------------------------------------
>
> Key: LUCENE-1990
> URL: https://issues.apache.org/jira/browse/LUCENE-1990
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: Flex Branch
> Reporter: Michael McCandless
> Priority: Minor
> Fix For: Flex Branch
>
> Attachments: generated_performance-te20100226.txt,
> LUCENE-1990-te20100122.patch, LUCENE-1990-te20100210.patch,
> LUCENE-1990-te20100212.patch, LUCENE-1990-te20100223.patch,
> LUCENE-1990-te20100226.patch, LUCENE-1990-te20100226b.patch,
> LUCENE-1990-te20100226c.patch, LUCENE-1990-te20100301.patch,
> LUCENE-1990.patch, LUCENE-1990.patch,
> LUCENE-1990_PerformanceMeasurements20100104.zip, perf-mkm-20100227.txt,
> performance-20100301.txt, performance-te20100226.txt
>
>
> There are various places in Lucene that could take advantage of an
> efficient packed unsigned int/long impl. EG the terms dict index in
> the standard codec in LUCENE-1458 could subsantially reduce it's RAM
> usage. FieldCache.StringIndex could as well. And I think "load into
> RAM" codecs like the one in TestExternalCodecs could use this too.
> I'm picturing something very basic like:
> {code}
> interface PackedUnsignedLongs {
> long get(long index);
> void set(long index, long value);
> }
> {code}
> Plus maybe an iterator for getting and maybe also for setting. If it
> helps, most of the usages of this inside Lucene will be "write once"
> so eg the set could make that an assumption/requirement.
> And a factory somewhere:
> {code}
> PackedUnsignedLongs create(int count, long maxValue);
> {code}
> I think we should simply autogen the code (we can start from the
> autogen code in LUCENE-1410), or, if there is an good existing impl
> that has a compatible license that'd be great.
> I don't have time near-term to do this... so if anyone has the itch,
> please jump!
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