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https://issues.apache.org/jira/browse/LUCENE-4547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13501436#comment-13501436
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Simon Willnauer commented on LUCENE-4547:
-----------------------------------------

bq. If an expert app really need to pick & choose ram vs disk dynamically, 
depending on how many other indices are open and how much RAM they are using, 
etc., they can always make a custom DV format ...

what I am worried about is the lack of communication between the app and the 
codec. something like this is going to be a major hassle. all I am asking about 
is to pass in "hints" to the codec what I need at a certain point per field. We 
can't do this and I think we shouldn't allow this. its an encoding / decoding 
layer and it should be simple. pushing what you call "experts" to write their 
own codecs is a major trap I think. writing a codec is last resort and causes 
major trouble for non-lucene devs IMO. This is expertexpert :)

I really like the idea of perfieldDV and I think we should do it. I am just not 
a big fan of making up-front decisions for this stuff when it comes to on-disk 
vs. ram. PostingsFormat is a different story, the on disk (low ram useage) have 
such a perf characteristics that you very unlikely need something else useing 
lots of ram. For sorting, grouping or scoring you will certainly need that.
                
> DocValues field broken on large indexes
> ---------------------------------------
>
>                 Key: LUCENE-4547
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4547
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>            Priority: Blocker
>             Fix For: 4.1
>
>         Attachments: test.patch
>
>
> I tried to write a test to sanity check LUCENE-4536 (first running against 
> svn revision 1406416, before the change).
> But i found docvalues is already broken here for large indexes that have a 
> PackedLongDocValues field:
> {code}
> final int numDocs = 500000000;
> for (int i = 0; i < numDocs; ++i) {
>   if (i == 0) {
>     field.setLongValue(0L); // force > 32bit deltas
>   } else {
>     field.setLongValue(1<<33L); 
>   }
>   w.addDocument(doc);
> }
> w.forceMerge(1);
> w.close();
> dir.close(); // checkindex
> {code}
> {noformat}
> [junit4:junit4]   2> WARNING: Uncaught exception in thread: Thread[Lucene 
> Merge Thread #0,6,TGRP-Test2GBDocValues]
> [junit4:junit4]   2> org.apache.lucene.index.MergePolicy$MergeException: 
> java.lang.ArrayIndexOutOfBoundsException: -65536
> [junit4:junit4]   2>  at 
> __randomizedtesting.SeedInfo.seed([5DC54DB14FA5979]:0)
> [junit4:junit4]   2>  at 
> org.apache.lucene.index.ConcurrentMergeScheduler.handleMergeException(ConcurrentMergeScheduler.java:535)
> [junit4:junit4]   2>  at 
> org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:508)
> [junit4:junit4]   2> Caused by: java.lang.ArrayIndexOutOfBoundsException: 
> -65536
> [junit4:junit4]   2>  at 
> org.apache.lucene.util.ByteBlockPool.deref(ByteBlockPool.java:305)
> [junit4:junit4]   2>  at 
> org.apache.lucene.codecs.lucene40.values.FixedStraightBytesImpl$FixedBytesWriterBase.set(FixedStraightBytesImpl.java:115)
> [junit4:junit4]   2>  at 
> org.apache.lucene.codecs.lucene40.values.PackedIntValues$PackedIntsWriter.writePackedInts(PackedIntValues.java:109)
> [junit4:junit4]   2>  at 
> org.apache.lucene.codecs.lucene40.values.PackedIntValues$PackedIntsWriter.finish(PackedIntValues.java:80)
> [junit4:junit4]   2>  at 
> org.apache.lucene.codecs.DocValuesConsumer.merge(DocValuesConsumer.java:130)
> [junit4:junit4]   2>  at 
> org.apache.lucene.codecs.PerDocConsumer.merge(PerDocConsumer.java:65)
> {noformat}

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