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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2555) Remove shared doc stores
Date Fri, 23 Jul 2010 16:26:50 GMT

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

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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