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From "Toke Eskildsen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1990) Add unsigned packed int impls in oal.util
Date Sat, 20 Feb 2010 21:52:28 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12836267#action_12836267
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Toke Eskildsen commented on LUCENE-1990:
----------------------------------------

I am sorry, but personal issues sapped my time and energy this week, so Lucene got bumped
down my priority-list. I am going to code4lib next week and I'll try and get some hacking
done in the plane from Denmark to USA, but that depends on whether or not there is a power
socket near my seat. If I don't upload a patch late monday, it will be early march before
I'll get it done

{quote}
But, now that we have getMutable, can we make the concrete impls
package private? Javadocs for Mutable.set should note that the size
is fixed once you allocate it.
{quote}

Agreed on both.

{quote}
We have no way to save a Mutable... should we add that?
{quote}

I dont know enough about persistence in Lucene to make that call. Since the writer is tied
to Lucene, it would not work for general purposes, so making a writer for Mutables only seems
to make sense if the user uses it to build index-structures?

{quote}
Maybe we should just merge Mutable & Reader, then? (LongStore?
LongArray? PackedLongs?)
{quote}

I don't understand that one? You made a compelling argument for returning immutables to readers
earlier (problems with concurrency and having all back ends support writes).

As for the name... I don't know. None of the sound right, but I have no other suggestion.

{quote}
We should state clearly that these are all unsigned ints storage.

Maybe rename PackedDirectInt to PackedDirect32 (and Short to 16,
Byte to 8). Because... while it is using a direct int[] under the hood,
it's really using all 32 bits for the full positive int range.
{quote}

Good point. The rest of your suggestions are also very valid.


> 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
>            Reporter: Michael McCandless
>            Priority: Minor
>         Attachments: LUCENE-1990-te20100122.patch, LUCENE-1990-te20100210.patch, LUCENE-1990-te20100212.patch,
LUCENE-1990.patch, LUCENE-1990_PerformanceMeasurements20100104.zip
>
>
> 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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