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https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13001214#comment-13001214
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Michael Busch commented on LUCENE-2881:
---------------------------------------

bq. maybe, we should store the FieldInfos inside the segments file? Hmmm....

I had the same thought while adding the ref to FieldInfos to SegmentInfo.  
Actually this is probably the right thing to do.  At the same time we could 
switch to a human-readable format :)


bq. I fear we may not necessarily ever "stabilize" on a fixed global 
name/number bimap, because we re-compute this map on every IW init?

We could also store the global map on disk?  addIndexes() would have to ignore 
the global map from the external index(es).



> 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, 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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