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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 20:55:59 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12992174#comment-12992174
] 

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

I gave the patch another glance - here are a couple of very minor comments:

* maybe we should return Iterable<FieldInfo> from FieldInfos#getFieldInfoIterator()
this would make the iteration syntactically more javaish 
{code} 

for (FieldInfo info : getFieldInfoIterator()) {
  // do something with it
}

{code}

* If we return Iterable<FieldInfo> should we name it getFieldInfos?
* Maybe we can simply implement Iterable<FieldInfo>?
* Maybe we can rename SI#clearFilesCache() to SI#clearCache() or simply SI#clear() this would
make thing less coupled to the SI internal cache but rather something that is called to clear
internal state after flush? 

> 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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