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https://issues.apache.org/jira/browse/LUCENE-2793?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13055649#comment-13055649
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Simon Willnauer commented on LUCENE-2793:
-----------------------------------------

bq. Should IOContext and MergeInfo be in oal.store not .index?
+1

bq. I think SegmentMerger should receive an IOCtx from its caller, and
yeah I think we should pass the IOContext in via the ctor. Yet, for 
IW#addIndexes you can simply build a best effort IOContext like:
{code}
 for (IndexReader indexReader : readers) {
   numDocs += indexReader.numDocs();
 }
 final IOContext context = new IOContext(new MergeInfo(numDocs, -1, true, 
false));
}

bq. I think on flush IOContext should include num docs and estimated
+1 I think that is good no?

bq. Somehow, lucene/contrib/demo/data is deleted on the branch. We should check 
if anything else is missing!
oh man... I will check

you use new IOContext(Context.FLUSH) and new IOContext(Context.READ) in your 
patch but we have some static like IOContext.READ maybe we need FLUSH too?

for the tests I think we should start randomizing the IOContext. I think you 
should add a newIOContext(Random random) to LuceneTestCase and get the context 
from there in a unit test. At the end of the day we should see same behavior 
whatever context you pass in right?

simon






> Directory createOutput and openInput should take an IOContext
> -------------------------------------------------------------
>
>                 Key: LUCENE-2793
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2793
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: core/store
>            Reporter: Michael McCandless
>            Assignee: Varun Thacker
>              Labels: gsoc2011, lucene-gsoc-11, mentor
>         Attachments: LUCENE-2793-nrt.patch, LUCENE-2793.patch, 
> LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, 
> LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, 
> LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, 
> LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch, LUCENE-2793.patch
>
>
> Today for merging we pass down a larger readBufferSize than for searching 
> because we get better performance.
> I think we should generalize this to a class (IOContext), which would hold 
> the buffer size, but then could hold other flags like DIRECT (bypass OS's 
> buffer cache), SEQUENTIAL, etc.
> Then, we can make the DirectIOLinuxDirectory fully usable because we would 
> only use DIRECT/SEQUENTIAL during merging.
> This will require fixing how IW pools readers, so that a reader opened for 
> merging is not then used for searching, and vice/versa.  Really, it's only 
> all the open file handles that need to be different -- we could in theory 
> share del docs, norms, etc, if that were somehow possible.

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