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From "Simon Willnauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2881) Track FieldInfo per segment instead of per-IW-session
Date Tue, 08 Feb 2011 20:23:57 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12992156#comment-12992156
] 

Simon Willnauer commented on LUCENE-2881:
-----------------------------------------

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

Wow! nice work Michael! I like how you preserve bw compat in SegmentInfo and FieldInfos is
now bound to SegmentInfo - yay! this solves two problems at once for DocValues branch.

bq.The alternative would be to rewrite the FieldInfos instead of just copying the files, but
then we have to rewrite the cfs files.

I think  copying over is fine. Ideally we will move all those boolean etc to the codec level
so that we don't need that at all. Once stored fields and vectors are written by the codec
we can push all that into PreFlex codec (maybe!?) and get rid of the bw compat code.

I think you should commit that patch. I'll port to docvalues and run some tests that rely
on this issue.

> 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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