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https://issues.apache.org/jira/browse/LUCENE-2555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12891659#action_12891659
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Michael McCandless commented on LUCENE-2555:
--------------------------------------------

{quote}

bq. What are the performance implications of removing shared doc stores?

I agree we have to test this when this patch is complete. My hope is that we 
save in other places (removing the interleaving step of the per-thread 
postings, no wait queue that serializes writing to doc stores) so that overall 
we won't be slower.
{quote}

Also, remember that shared doc stores is not as good an opto as it used to be, 
because we are now able to bulk-copy both stored fields and term vectors during 
merging.

However, bulk merging only happens if the field name -> number mapping is 
congruent, b/w the merged segment and the one segment being merged.

Unfortunately, you can easily unexpectedly break this (see LUCENE-1737) but eg 
adding diff't fields to your docs, or adding same fields just in a different 
order.

> Remove shared doc stores
> ------------------------
>
>                 Key: LUCENE-2555
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2555
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Michael Busch
>            Assignee: Michael Busch
>            Priority: Minor
>             Fix For: Realtime Branch
>
>
> With per-thread DocumentsWriters sharing doc stores across segments doesn't 
> make much sense anymore.
> See also LUCENE-2324.

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