prepareCommit vs Commit

[Phani Chaitanya <pv...@gmail.com>]

Hi all, 

  I'd like to know a bit more in detail about what is happening behind the
scenes in case of prepareCommit vs Commit. 

Also, I read that if a indexing request comes while commit is requested, it
opens a new segment for the indexing and commit happens as usual. So, the
question is when would a new segment be opened for indexing ? Is it part of
prepareCommit/Commit ? If so, why ?

Thanks.



-----
Phani Chaitanya
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Re: prepareCommit vs Commit

[Michael McCandless <lu...@mikemccandless.com>]

prepareCommit flushes any buffered docs (in RAM) to a new segment,
applies all deletes, fsync's the new files, writes all but the last 4
checksum bytes of the segments file.

Ie, it tries to do everything possible short of finishing the commit
up front, so that if there will be a problem, e.g. disk full, you
should hit it during prepareCommit.  But, an external reader opening
the index at this point will still not see the commit.

Then, commit writes the last 4 checksum bytes, closes the segments
file and syncs it, so that the commit is now visible to any newly
opened reader.

Any indexing requests that arrive while a commit is underway may or
may not make it into the commit; it depends how the threads are
scheduled.  If they don't make it into the commit then they will just
be buffered up for the next commit.

Lucene still writes segment files when commit is not called, e.g. when
the RAM buffer is full.

Mike McCandless

http://blog.mikemccandless.com


On Wed, Oct 16, 2013 at 11:37 AM, Phani Chaitanya
<pv...@gmail.com> wrote:
> Hi all,
>
>   I'd like to know a bit more in detail about what is happening behind the
> scenes in case of prepareCommit vs Commit.
>
> Also, I read that if a indexing request comes while commit is requested, it
> opens a new segment for the indexing and commit happens as usual. So, the
> question is when would a new segment be opened for indexing ? Is it part of
> prepareCommit/Commit ? If so, why ?
>
> Thanks.
>
>
>
> -----
> Phani Chaitanya
> --
> View this message in context: http://lucene.472066.n3.nabble.com/prepareCommit-vs-Commit-tp4095917.html
> Sent from the Lucene - Java Users mailing list archive at Nabble.com.
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: java-user-unsubscribe@lucene.apache.org
> For additional commands, e-mail: java-user-help@lucene.apache.org
>

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