[jira] [Updated] (LUCENE-5152) Lucene FST is not immutale

["Simon Willnauer (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LUCENE-5152?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Simon Willnauer updated LUCENE-5152:
------------------------------------

    Attachment: LUCENE-5152.patch

here is a patch that adds a #deepCopy method to Outputs that allows me to do a deep copy if the actual arc that is returned is a cached root arc. I think we should never return a pointer into the root arcs though. this is way to dangerous! I haven't run any perf tests will do once I am on my worksstation again.. if somebody beats me go ahead!
                
> Lucene FST is not immutale
> --------------------------
>
>                 Key: LUCENE-5152
>                 URL: https://issues.apache.org/jira/browse/LUCENE-5152
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: core/FSTs
>    Affects Versions: 4.4
>            Reporter: Simon Willnauer
>            Priority: Blocker
>             Fix For: 5.0, 4.5
>
>         Attachments: LUCENE-5152.patch, LUCENE-5152.patch
>
>
> a spinnoff from LUCENE-5120 where the analyzing suggester modified a returned output from and FST (BytesRef) which caused sideffects in later execution. 
> I added an assertion into the FST that checks if a cached root arc is modified and in-fact this happens for instance in our MemoryPostingsFormat and I bet we find more places. We need to think about how to make this less trappy since it can cause bugs that are super hard to find.

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