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https://issues.apache.org/jira/browse/LUCENE-4203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13409832#comment-13409832
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Michael McCandless commented on LUCENE-4203:
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bq. Should we consider splitting out NRTSegmentReader and just make it
type-safe?
Hmm interesting...
I think we shouldn't: the only reason why IW must be in NRT mode (pooling
readers) is because of a limitation of IW: it cannot buffer pending deleted
docIDs against already-flushed segments unless it has a pooled reader for that
segment.
We could (should?) someday fix this limitation, so I don't think the API sig
should lock it down today.
I also don't want users to think there may be salient differences b/w an NRT
reader and a "normal" reader. The only difference is how the reader got the
list of segments it should open ... otherwise an NRT reader and non-NRT reader
are identical now.
> Add IndexWriter.tryDeleteDocument, to delete by document id when possible
> -------------------------------------------------------------------------
>
> Key: LUCENE-4203
> URL: https://issues.apache.org/jira/browse/LUCENE-4203
> Project: Lucene - Java
> Issue Type: Improvement
> Components: core/index
> Reporter: Michael McCandless
> Attachments: LUCENE-4203.patch
>
>
> Spinoff from LUCENE-4069.
> In that use case, where the app needs to first lookup a document, then
> call updateDocument, it's wasteful today because the relatively costly
> lookup (by a primary key field, eg "id") is done twice.
> But, since you already resolved the PK to docID on the first lookup,
> it would be nice to then delete by that docID and then you can call
> addDocument instead.
> So I worked out a rough start at this, by adding
> IndexWriter.tryDeleteDocument. It'd be a very expert API: it takes a
> SegmentInfo (referencing the segment that contains the docID), and as
> long as that segment hasn't yet been merged away, it will mark the
> document for deletion and return true (success). If it has been
> merged away it returns false and the app must then delete-by-term. It
> only works if the writer is in NRT mode (ie you've opened an NRT
> reader).
> In LUCENE-4069 using tryDeleteDocument gave a ~20% net speedup.
> I think tryDeleteDocument would also be useful when Solr "updates" a
> document by loading all stored fields, changing them, and calling
> updateDocument.
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