lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Michael Busch (JIRA)" <>
Subject [jira] Commented: (LUCENE-2324) Per thread DocumentsWriters that write their own private segments
Date Tue, 18 Jan 2011 19:32:45 GMT


Michael Busch commented on LUCENE-2324:

bq. Why does DW.anyDeletions need to be sync'd?

Hmm good point.  Actually only the call to DW.pendingDeletes.any() needs to be synced, but
not the loop that calls the DWPTs.

In ThreadAffinityDWTP... it may be better if we had a single queue,
where threads wait in line, if no DWPT is available? And when a DWPT
finishes it then notifies any waiting threads? (Ie, instead of queue-per-DWPT).

Whole foods instead of safeway? :)
Yeah that would be fairer.  A large doc (= a full cart) wouldn't block unlucky other docs.
 I'll make that change, good idea!

I see the fieldInfos.update(dwpt.getFieldInfos()) (in
DW.updateDocument) - is there a risk that two threads bring a new
field into existence at the same time, but w/ different config? Eg
one doc omitsTFAP and the other doesn't? Or, on flush, does each DWPT
use its private FieldInfos to correctly flush the segment? (Hmm: do
we seed each DWPT w/ the original FieldInfos created by IW on init?).

Every DWPT has its own private FieldInfos.  When a segment is flushed the DWPT uses its private
FI and then it updates the original DW.fieldInfos (from IW), which is a synchronized call.

The only consumer of DW.getFieldInfos() is SegmentMerger in IW.  Hmm, given that IW.flush()
isn't synchronized anymore I assume this can lead into a problem?  E.g. the SegmentMerger
gets a FieldInfos that's "newer" than the list of segments it's trying to flush?

bq. How are we handling the case of open IW, do delete-by-term but no added docs?

DW has a SegmentDeletes (pendingDeletes) which gets pushed to the last segment.  We only add
delTerms to DW.pendingDeletes if we couldn't push it to any DWPT.  Btw. I think the whole
pushDeletes business isn't working correctly yet, I'm looking into it.  I need to understand
the code that coalesces the deletes better. 

bq. In DW.deleteTerms... shouldn't we skip a DWPT if it has no buffered docs?

Yeah, I did that already, but not committed yet.

> 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: Realtime Branch
>         Attachments: LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch,
LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch, LUCENE-2324.patch, LUCENE-2324.patch, LUCENE-2324.patch,
lucene-2324.patch, lucene-2324.patch, LUCENE-2324.patch, test.out, test.out, test.out, test.out
> 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.

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

To unsubscribe, e-mail:
For additional commands, e-mail:

View raw message