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From "Jason Rutherglen (JIRA)" <>
Subject [jira] Commented: (LUCENE-2324) Per thread DocumentsWriters that write their own private segments
Date Wed, 21 Apr 2010 20:17:52 GMT


Jason Rutherglen commented on LUCENE-2324:

{quote}flushing by maxBufferedDeleteTerms is also tricky,
because that needs to be a flush across all DWPTs{quote}

I think we simply keep track of maxBufferedDocs and
maxBufferedDeleteTerms globally. We can't deprecate because
that'd be a pain for users. 

{quote}With searchable RAM buffers and deletes in the foreground
this trigger should actually not be necessary anymore?{quote}

The deletes aren't entirely in the foreground, only the RAM
buffer deletes. Deletes to existing segments would use the
existing clone and delete mechanism. I asked about foreground
deletes to existing segments before, and we agreed that it's not
a good idea due to locality of terms/postings.

{quote}We would probably apply deletes when the realtime
IndexReader is (re)opened?{quote}

Right, that's how the existing apply deletes basically works.
That'd be the same. Oh ok, I see, perhaps the global deletes
manager could cache the deletes for the existing segments, the
DWPTs can keep track of their deletes separately. We probably
won't apply segment or DWPT deletes in the foreground? We'd
cache them separately, and update ram consumption and unique
term/query counts globally. 

> Per thread DocumentsWriters that write their own private segments
> -----------------------------------------------------------------
>                 Key: LUCENE-2324
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Michael Busch
>            Assignee: Michael Busch
>            Priority: Minor
>             Fix For: 3.1
>         Attachments: lucene-2324.patch, LUCENE-2324.patch
> See LUCENE-2293 for motivation and more details.
> I'm copying here Mike's summary he posted on 2293:
> Change the approach for how we buffer in RAM to a more isolated
> approach, whereby IW has N fully independent RAM segments
> in-process and when a doc needs to be indexed it's added to one of
> them. Each segment would also write its own doc stores and
> "normal" segment merging (not the inefficient merge we now do on
> flush) would merge them. This should be a good simplification in
> the chain (eg maybe we can remove the *PerThread classes). The
> segments can flush independently, letting us make much better
> concurrent use of IO & CPU.

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