[jira] [Commented] (LUCENE-6279) 3.x -> 4.x .si upgrade should not be tricked by leftover upgrade marker file

["Michael McCandless (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-6279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14331963#comment-14331963 ] 

Michael McCandless commented on LUCENE-6279:
--------------------------------------------

I've thought about a couple ways to fix this.

We could fix SIS to record on read that it was pre-4.0, and then on write it upgrades any 3.x segments.  This is kinda a big change, though, and I don't get why we do it today on every commit ... is there any way for a 3.x segment to sneak in to a 4.x SIS un-upgraded?  IW.addIndexes(Dir[]) writes upgrades .si ...

A less scary change would be to just check the SI.files() to see whether the .si file is in there; if it is, it was already upgraded.  Then we could remove the marker file entirely.

Yet another maybe even less scary option would be to keep writing the marker file, but check if it's already in SI.files() (instead of trying to open it from the filesystem) to see whether we already upgraded...

> 3.x -> 4.x .si upgrade should not be tricked by leftover upgrade marker file
> ----------------------------------------------------------------------------
>
>                 Key: LUCENE-6279
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6279
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>             Fix For: 4.10.x
>
>         Attachments: LUCENE-6279.patch
>
>
> Today when you do the first IW.commit to a 3.x index from Lucene 4.x, we go
> through a per-segment upgrade process when writing the next segments_N
> file, writing .si files for each segment if we didn't already do so.
> However, this process can be fooled by a leftover _N_upgraded.si
> file, in case the app above Lucene wasn't careful and reused a
> directory that had leftover files... I think we can make this more
> robust.



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