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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-6383) MemoryPostings fst encoding can be surprisingly inefficient (especially in tests, with payloads)
Date Wed, 01 Apr 2015 10:08:53 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-6383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14390318#comment-14390318
] 

Robert Muir commented on LUCENE-6383:
-------------------------------------

In this case merging creates a bigger index. 300 KB of segments becomes a 450KB single segment.
So its not the same problem exactly...

> MemoryPostings fst encoding can be surprisingly inefficient (especially in tests, with
payloads)
> ------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-6383
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6383
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>
> I just worked around this in 2 nightly OOM fails.
> One was TestDuelingCodecs, the other was TestIndexWriterForceMerge's space usage test.
> In general the trend is the same, it seems the more documents you merge, you just get
bigger and bigger FST outputs and the size of this PF in ram and on disk grows in a way you
don't expect. E.g. merging 300KB of segments resulted in 450KB single segment, and memory
usage gets absurdly high.
> The issue seems especially aggravated in tests, when MockAnalyzer adds lots of payloads.
> Maybe it should encode the postings data in a more efficient way? Can it just use a Long
output pointing into a RAMFile or something? Or maybe there is just a crazy bug?



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