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https://issues.apache.org/jira/browse/LUCENE-2026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12788838#action_12788838
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Earwin Burrfoot commented on LUCENE-2026:
-----------------------------------------
We need an ability to see segment write (and probably deleted doc list write)
as a discernible atomic operation. Right now it looks like several file writes,
and we can't, say - redirect all files belonging to a certain segment to
another Directory (well, in a simple manner). 'Something' should sit between a
Directory (or several Directories) and IndexWriter.
If we could do this, the current NRT search implementation will be largely
obsoleted, innit? Just override the default impl of 'something' and send
smaller segments to ram, bigger to disk, copy ram segments to disk
asynchronously if we want to. Then we can use your granma's IndexReader and
IndexWriter, totally decoupled from each other, and have blazing fast
addDocument-commit-reopen turnaround.
> Refactoring of IndexWriter
> --------------------------
>
> Key: LUCENE-2026
> URL: https://issues.apache.org/jira/browse/LUCENE-2026
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Reporter: Michael Busch
> Assignee: Michael Busch
> Priority: Minor
> Fix For: 3.1
>
>
> I've been thinking for a while about refactoring the IndexWriter into
> two main components.
> One could be called a SegmentWriter and as the
> name says its job would be to write one particular index segment. The
> default one just as today will provide methods to add documents and
> flushes when its buffer is full.
> Other SegmentWriter implementations would do things like e.g. appending or
> copying external segments [what addIndexes*() currently does].
> The second component's job would it be to manage writing the segments
> file and merging/deleting segments. It would know about
> DeletionPolicy, MergePolicy and MergeScheduler. Ideally it would
> provide hooks that allow users to manage external data structures and
> keep them in sync with Lucene's data during segment merges.
> API wise there are things we have to figure out, such as where the
> updateDocument() method would fit in, because its deletion part
> affects all segments, whereas the new document is only being added to
> the new segment.
> Of course these should be lower level APIs for things like parallel
> indexing and related use cases. That's why we should still provide
> easy to use APIs like today for people who don't need to care about
> per-segment ops during indexing. So the current IndexWriter could
> probably keeps most of its APIs and delegate to the new classes.
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