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https://issues.apache.org/jira/browse/LUCENE-2026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12789614#action_12789614
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Marvin Humphrey commented on LUCENE-2026:
-----------------------------------------
> I say it's better to sacrifice write guarantee.
I don't grok why sync is the default, especially given how sketchy hardware
drivers are about obeying fsync:
{panel}
But, beware: some hardware devices may in fact cache writes even during
fsync, and return before the bits are actually on stable storage, to give
the
appearance of faster performance.
{panel}
IMO, it should have been an option which defaults to false, to be enabled only
by
users who have the expertise to ensure that fsync() is actually doing what
it advertises. But what's done is done (and Lucy will probably just do
something
different.)
With regard to Lucene NRT, though, turning sync() off would really help. If
and
when some sort of settings class comes about, an enableSync(boolean enabled)
method seems like it would come in handy.
> 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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