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Posted to dev@lucene.apache.org by "Michael McCandless (JIRA)" <ji...@apache.org> on 2009/04/04 14:21:13 UTC
[jira] Commented: (LUCENE-1585) Allow to control how payloads are
merged
[ https://issues.apache.org/jira/browse/LUCENE-1585?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12695728#action_12695728 ]
Michael McCandless commented on LUCENE-1585:
--------------------------------------------
I agree: extensibility to the SegmentInfo (just like FieldInfo) is needed.
I think, ideally, with LUCENE-1458 there would be a "payloads codec" responsible for reading & writing & merging. All things (not just payloads) need this.
EG, because the payload is opaque to Lucene, we now must encode the length of the byte[] per term occurrence, but if [say] the codec knows it's always N bytes, or it's a function of term, or something, the codec would be free not to encode the number of bytes and derive it from other sources.
> Allow to control how payloads are merged
> ----------------------------------------
>
> Key: LUCENE-1585
> URL: https://issues.apache.org/jira/browse/LUCENE-1585
> Project: Lucene - Java
> Issue Type: New Feature
> Components: Index
> Reporter: Michael Busch
> Assignee: Michael Busch
> Priority: Minor
>
> Lucene handles backwards-compatibility of its data structures by
> converting them from the old into the new formats during segment
> merging.
> Payloads are simply byte arrays in which users can store arbitrary
> data. Applications that use payloads might want to convert the format
> of their payloads in a similar fashion. Otherwise it's not easily
> possible to ever change the encoding of a payload without reindexing.
> So I propose to introduce a PayloadMerger class that the SegmentMerger
> invokes to merge the payloads from multiple segments. Users can then
> implement their own PayloadMerger to convert payloads from an old into
> a new format.
> In the future we need this kind of flexibility also for column-stride
> fields (LUCENE-1231) and flexible indexing codecs.
> In addition to that it would be nice if users could store version
> information in the segments file. E.g. they could store "in segment _2
> the term a:b uses payloads of format x.y".
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