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Posted to dev@lucene.apache.org by "Michael McCandless (JIRA)" <ji...@apache.org> on 2011/07/09 15:03:16 UTC
[jira] [Commented] (LUCENE-3297) FST doesn't fully share common
prefix across all outputs
[ https://issues.apache.org/jira/browse/LUCENE-3297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13062369#comment-13062369 ]
Michael McCandless commented on LUCENE-3297:
--------------------------------------------
I don't plan to work on this any time soon... I think it's low priority.
> FST doesn't fully share common prefix across all outputs
> --------------------------------------------------------
>
> Key: LUCENE-3297
> URL: https://issues.apache.org/jira/browse/LUCENE-3297
> Project: Lucene - Java
> Issue Type: Improvement
> Reporter: Michael McCandless
> Priority: Minor
>
> FST will try to share prefixes of outputs when possible, however in the [I think unusual in practice] case where all outputs share a common prefix, FST really ought to store this just once, on the root arc, but instead it's only able to push back to the N root arcs. It's sort of an off-by-one on how far back the pushing goes...
> One [synthetic] example where this makes a big difference is the new Test2BPostings test, when it uses MemoryCodec, because this test has 26 terms (letters of alphabet) and each term has exactly the same long (~85 MB) all 1s byte[] as the postings. If we fixed this issue, then the resulting FST would only be ~85 MB but now instead it needs to be ~85 * 26 MB.
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