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https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000180#comment-13000180
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Simon Willnauer commented on LUCENE-2881:
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Thanks for the clarification, michael!
bq. ... the smallest number available in the local map is picked (to keep the
numbers dense). ...
Oh man I was not aware of this. I got totally confused... see next comment
{quote}
Hmm, after writing this example down I'm realizing that it would be better to
just always pick the next available global field number for a new field, then,
at least until we get DWPTs, we should never get different numbers across
segments, I think? The disadvantage would be that FieldInfos could have "gaps"
in the numbers. I implemented the current approach because I wanted to avoid
those gaps, but having them would probably not be a big deal?
{quote}
This is how I thought it works but I obviously got confused by global vs. local
this is also why I had trouble to understand how that failure could ever have
happened. But after looking at the code again this makes sense ;) I don't see
any problems in FieldInfo number gaps. this should work just fine and guarantee
the bulk copy just for now at least.
> Track FieldInfo per segment instead of per-IW-session
> -----------------------------------------------------
>
> Key: LUCENE-2881
> URL: https://issues.apache.org/jira/browse/LUCENE-2881
> Project: Lucene - Java
> Issue Type: Improvement
> Affects Versions: Realtime Branch, CSF branch, 4.0
> Reporter: Simon Willnauer
> Assignee: Michael Busch
> Fix For: Realtime Branch, CSF branch, 4.0
>
> Attachments: lucene-2881.patch, lucene-2881.patch, lucene-2881.patch,
> lucene-2881.patch, lucene-2881.patch
>
>
> Currently FieldInfo is tracked per IW session to guarantee consistent global
> field-naming / ordering. IW carries FI instances over from previous segments
> which also carries over field properties like isIndexed etc. While having
> consistent field ordering per IW session appears to be important due to bulk
> merging stored fields etc. carrying over other properties might become
> problematic with Lucene's Codec support. Codecs that rely on consistent
> properties in FI will fail if FI properties are carried over.
> The DocValuesCodec (DocValuesBranch) for instance writes files per segment
> and field (using the field id within the file name). Yet, if a segment has no
> DocValues indexed in a particular segment but a previous segment in the same
> IW session had DocValues, FieldInfo#docValues will be true since those
> values are reused from previous segments.
> We already work around this "limitation" in SegmentInfo with properties like
> hasVectors or hasProx which is really something we should manage per Codec &
> Segment. Ideally FieldInfo would be managed per Segment and Codec such that
> its properties are valid per segment. It also seems to be necessary to bind
> FieldInfoS to SegmentInfo logically since its really just per segment
> metadata.
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