lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2881) Track FieldInfo per segment instead of per-IW-session
Date Mon, 28 Feb 2011 11:17:37 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000229#comment-13000229
] 

Michael McCandless commented on LUCENE-2881:
--------------------------------------------

This was an impressive change :)  Not only did we shift FieldInfos under SegmentInfo, we also
fixed a given FieldInfos to allow for sparse mapping (ie, it only contains certain field numbers).
 Various places previously assumed this was a dense mapping.

I think even in the DWPT case we should try to assign consistent field numbers?  I'm already
worried enough about the possible perf hit DWPT will put on normal indexing and the NRT case,
since it basically pushes merging out from RAM and onto the "normal" more costly disk based
merging.  If we also suddenly risk these merges not being bulk merges, that's even worse.

Can't we sync globally on the assignment of field name -> number (the global map lookup)?
 And FieldInfos per-DWPT would share the same global map.  Wouldn't that keep us consistent
in the DWPT case?

> 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.  

-- 
This message is automatically generated by JIRA.
-
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org


Mime
View raw message