lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Jason Rutherglen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2680) Improve how IndexWriter flushes deletes against existing segments
Date Mon, 29 Nov 2010 20:59:13 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12964938#action_12964938
] 

Jason Rutherglen commented on LUCENE-2680:
------------------------------------------

bq. The waitReady(null) is there so that DW.pauseAllThreads also pauses any threads doing
deletions

waitReady is used in getThreadState as well as bufferDeleteX, we may need to redundantly add
it to SegmentDeletes?  Maybe not.  We'll be sync'ing on IW when adding deletions, that seems
like it'll be OK.  

{quote}in moving these methods to IW, we'd make them sync on IW (they are now sync'd on DW),
which takes care of pausing these threads{quote}

Because we're sync'ing on IW we don't need to pause the indexing threads?  Ok this is because
doFlushX is sync'd on IW.  

{quote}The RAM accounting can be done fully inside IW.{quote}

Well, inside of SegmentDeletes.

> Improve how IndexWriter flushes deletes against existing segments
> -----------------------------------------------------------------
>
>                 Key: LUCENE-2680
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2680
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Michael McCandless
>             Fix For: 4.0
>
>         Attachments: LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch,
LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch,
LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch
>
>
> IndexWriter buffers up all deletes (by Term and Query) and only
> applies them if 1) commit or NRT getReader() is called, or 2) a merge
> is about to kickoff.
> We do this because, for a large index, it's very costly to open a
> SegmentReader for every segment in the index.  So we defer as long as
> we can.  We do it just before merge so that the merge can eliminate
> the deleted docs.
> But, most merges are small, yet in a big index we apply deletes to all
> of the segments, which is really very wasteful.
> Instead, we should only apply the buffered deletes to the segments
> that are about to be merged, and keep the buffer around for the
> remaining segments.
> I think it's not so hard to do; we'd have to have generations of
> pending deletions, because the newly merged segment doesn't need the
> same buffered deletions applied again.  So every time a merge kicks
> off, we pinch off the current set of buffered deletions, open a new
> set (the next generation), and record which segment was created as of
> which generation.
> This should be a very sizable gain for large indices that mix
> deletes, though, less so in flex since opening the terms index is much
> faster.

-- 
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: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org


Mime
View raw message