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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-2881) Track FieldInfo per segment instead of per-IW-session
Date Tue, 08 Feb 2011 20:11:57 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Michael Busch updated LUCENE-2881:
----------------------------------

    Attachment: lucene-2881.patch

New patch that removes the tracking of 'hasVectors' and 'hasProx' in SegmentInfo.  Instead
SegmentInfo now has a reference to its corresponding FieldInfos.  

For backwards-compatibility reasons we can't completely remove the hasVectors and hasProx
bytes from the serialized SegmentInfo yet.  Eg. if someone uses addIndexes(Directory...) to
add external old pre-4.0 segments to a new index, we "upgrade" the SegmentInfo to the latest
version.  However, we don't modify the FieldInfos of that segment, instead we just copy it
over to the new dir.  So the hasVector and hasProx bits in the FieldInfos might not be accurate
and we have to keep those bits in the SegmentInfo instead.  Not an ideal solution, but we
can remove it entirely in Lucene 5.0 :).  The alternative would be to
rewrite the FieldInfos instead of just copying the files, but then we have to rewrite the
cfs files.

All core & contrib tests pass.

> 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
>
>
> 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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