[
https://issues.apache.org/jira/browse/LUCENE-994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12530401
]
Michael McCandless commented on LUCENE-994:
-------------------------------------------
This is certainly not expected!
So you are flushing by RAM usage, and then find that merging according
to doc count gives substantially better performance than merging
according to byte size of the segments?
I'll run a test with contrib/benchmark on wikipedia content. I'll set
mergeFactor to 3 and ramBufferMB = 42 and I'll optimize in the end.
Is there anything else interesting in how you're using Lucene?
Do you have any sense of where this sizable slowdown shows up? EG, is
the optimize in the end substantially slower, or something?
Is there any way to tease out the time actually spent in Lucene vs the
rest of your application?
> Change defaults in IndexWriter to maximize "out of the box" performance
> -----------------------------------------------------------------------
>
> Key: LUCENE-994
> URL: https://issues.apache.org/jira/browse/LUCENE-994
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.3
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Priority: Minor
> Fix For: 2.3
>
> Attachments: LUCENE-994.patch
>
>
> This is follow-through from LUCENE-845, LUCENE-847 and LUCENE-870;
> I'll commit this once those three are committed.
> Out of the box performance of IndexWriter is maximized when flushing
> by RAM instead of a fixed document count (the default today) because
> documents can vary greatly in size.
> Likewise, merging performance should be faster when merging by net
> segment size since, to minimize the net IO cost of merging segments
> over time, you want to merge segments of equal byte size.
> Finally, ConcurrentMergeScheduler improves indexing speed
> substantially (25% in a simple initial test in LUCENE-870) because it
> runs the merges in the backround and doesn't block
> add/update/deleteDocument calls. Most machines have concurrency
> between CPU and IO and so it makes sense to default to this
> MergeScheduler.
> Note that these changes will break users of ParallelReader because the
> parallel indices will no longer have matching docIDs. Such users need
> to switch IndexWriter back to flushing by doc count, and switch the
> MergePolicy back to LogDocMergePolicy. It's likely also necessary to
> switch the MergeScheduler back to SerialMergeScheduler to ensure
> deterministic docID assignment.
> I think the combination of these three default changes, plus other
> performance improvements for indexing (LUCENE-966, LUCENE-843,
> LUCENE-963, LUCENE-969, LUCENE-871, etc.) should make for some sizable
> performance gains Lucene 2.3!
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
