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Date: Mon, 18 Oct 2010 16:40:26 -0400 (EDT)
From: "Jason Rutherglen (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-2575) Concurrent byte and int block
 implementations
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    [ https://issues.apache.org/jira/browse/LUCENE-2575?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12922243#action_12922243 ] 

Jason Rutherglen commented on LUCENE-2575:
------------------------------------------

The other unique thing implemented in the Twitter search as described by the shared slides, is each posting is a single int.  This makes it fairly simply to detect if a posting has been written because if it hasn't, it'll be 0 or some other pre-init'd value.  However given our postings contain multiple vints, payloads, and we have both freq and prox streams, I don't think we can properly detect while reading if a given posting has in fact been completely written.  We'd maybe need a posting verification check, like writing the posting to a buffer first, then writing the buffer with it's length at the beginning.   That's unnecessarily complex if system array copy is fast enough for copying between a write and read upto array.

> Concurrent byte and int block implementations
> ---------------------------------------------
>
>                 Key: LUCENE-2575
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2575
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: Realtime Branch
>            Reporter: Jason Rutherglen
>             Fix For: Realtime Branch
>
>         Attachments: LUCENE-2575.patch, LUCENE-2575.patch, LUCENE-2575.patch, LUCENE-2575.patch, LUCENE-2575.patch
>
>
> The current *BlockPool implementations aren't quite concurrent.
> We really need something that has a locking flush method, where
> flush is called at the end of adding a document. Once flushed,
> the newly written data would be available to all other reading
> threads (ie, postings etc). I'm not sure I understand the slices
> concept, it seems like it'd be easier to implement a seekable
> random access file like API. One'd seek to a given position,
> then read or write from there. The underlying management of byte
> arrays could then be hidden?

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