I think you still need to close the IndexWriter at some point, in
order to search the new documents. In effect all of the changes using
the "buffered" IndexWriter are meaningless until the IndexWriter is
closed and a new IndexReader opened.
Given that, it doesn't make much difference when you do the buffering...
My statement about getting the lock once was not entirely correct as
you point out, it needs to be grabbed in two stages, but a far more
simple design (as I proposed) could be used - obviously some changes
for lock management would be needed.
I DO think that the deletion code should be moved to IndexWriter - it
makes more sense there. The current design IS a bit goofy... I don't
see why you would delete using an IndexReader.... - why be able to
see deletions in the current IndexReader but not be able to see
additions? What is the benefit?
I really like the idea of the BufferedWriter - it is similar to what
is proposed but I think the implementation would be far simpler and
more straightforward. It would be similar to IndexModifier without
the warning that you should do all the deletions first, and then all
the additions - the BufferedWriter would manage this for you.
On Jul 6, 2006, at 9:16 PM, Chuck Williams wrote:
Robert,
Either you or I are missing something basic. I'm not sure which.
As I understand things, an IndexWriter and an IndexReader cannot both
have the write lock at the same time (they use the same write lock
file
name). Only an IndexReader can delete and only an IndexWriter can
add.
So to update, you need to close the IndexWriter, have the IndexReader
delete, and then reopen the IndexWriter. With the patch, you never
need
to close the IndexWriter, as I said before. This provides a
benefit in
cases where updates cannot be combined into large batches. In this
case
without the patch the IndexWriter must be closed and reopened
frequently, whereas with the patch it does not.
Have I got something wrong?
Chuck
robert engels wrote on 07/06/2006 03:08 PM:
I think I finally see how this is supposed to optimize - basically
because it remember the terms, and then does the batch deletions.
We avoid all of this messiness by just making sure each document
has a
primary key and we always remove/update by primary key and we can
keep
the operations in an ordered list (actually set since the keys are
unique, and that way multiple updates to the same document in a batch
can be coalesced).
I guess still don't see why the change is so involved though...
I would just maintain an ordered list of operations (deletes an adds)
on the "buffered writer".
When the "buffered" writer is closed:
Create a RamDirectory.
Perform all deletions in a batch on the main IndexReader.
Perform ordered deletes and adds on the RamDirectory.
Merge the RamDirectory with the main index.
This could all be encapsulated in a BufferedIndexWriter class.
On Jul 6, 2006, at 4:34 PM, robert engels wrote:
I guess I don't see the difference...
You need the write lock to use the indexWriter, and you also need
the
write lock to perform a deletion, so if you just get the write lock
you can perform the deletion and the add, then close the writer.
I have asked how this submission optimizes anything, and I still
can't seem to get an answer?
On Jul 6, 2006, at 4:27 PM, Otis Gospodnetic wrote:
I think that patch is for a different scenario, the one where you
can't wait to batch deletes and adds, and want/need to execute them
more frequently and in order they really are happening, without
grouping them.
Otis
----- Original Message ----
From: robert engels <[EMAIL PROTECTED]>
To: java-dev@lucene.apache.org
Sent: Thursday, July 6, 2006 3:24:13 PM
Subject: Re: [jira] Commented: (LUCENE-565) Supporting
deleteDocuments in IndexWriter (Code and Performance Results
Provided)
I guess we just chose a much simpler way to do this...
Even with you code changes, to see the modification made using the
IndexWriter, it must be closed, and a new IndexReader opened.
So a far simpler way is to get the collection of updates first,
then
using opened indexreader,
for each doc in collection
delete document using "key"
endfor
open indexwriter
for each doc in collection
add document
endfor
open indexreader
I don't see how your way is any faster. You must always flush to
disk
and open the indexreader to see the changes.
On Jul 6, 2006, at 2:07 PM, Ning Li wrote:
Hi Otis and Robert,
I added an overview of my changes in JIRA. Hope that helps.
Anyway, my test did exercise the small batches, in that in our
incremental updates we delete the documents with the unique
term, and
then add the new (which is what I assumed this was improving),
and I
saw o appreciable difference.
Robert, could you describe a bit more how your test is set up?
Or a
short
code snippet will help me explain.
Without the patch, when inserts and deletes are interleaved in
small
batches, the performance can degrade dramatically because the
ramDirectory
is flushed to disk whenever an IndexWriter is closed, causing a
lot of
small segments to be created on disk, which eventually need to be
merged.
Is this how your test is set up? And, what are the maxBufferedDocs
and the
maxBufferedDeleteTerms in your test? You won't see a performance
improvement
if they are about the same as the small batch size. The patch
works by
internally buffering inserts and deletes into larger batches.
Regards,
Ning
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