I applied the patch, and made code changes to use it. It did not make
any appreciable difference in performance over our current code
(delete using IndexReader and then update the documents using
IndexWriter - each document has a unique "key").
I attempted to evaluate the code on its own, but must admit that I
got "lost" a bit.
Maybe if the submitter could provide a "design overview" of why this
is more efficient, and in what cases it is (and possible degradation
in others) it would be easier to evaluate.
On Jul 5, 2006, at 10:25 PM, Otis Gospodnetic (JIRA) wrote:
[ http://issues.apache.org/jira/browse/LUCENE-565?
page=comments#action_12419396 ]
Otis Gospodnetic commented on LUCENE-565:
-----------------------------------------
I took a look at the patch and it looks good to me (anyone else had
a look)?
Unfortunately, I couldn't get the patch to apply :(
$ patch -F3 < IndexWriter.patch
(Stripping trailing CRs from patch.)
patching file IndexWriter.java
Hunk #1 succeeded at 58 with fuzz 1.
Hunk #2 succeeded at 112 (offset 2 lines).
Hunk #4 succeeded at 504 (offset 33 lines).
Hunk #6 succeeded at 605 with fuzz 2 (offset 57 lines).
missing header for unified diff at line 259 of patch
(Stripping trailing CRs from patch.)
can't find file to patch at input line 259
Perhaps you should have used the -p or --strip option?
The text leading up to this was:
...
...
...
File to patch: IndexWriter.java
patching file IndexWriter.java
Hunk #1 FAILED at 802.
Hunk #2 succeeded at 745 with fuzz 2 (offset -131 lines).
1 out of 2 hunks FAILED -- saving rejects to file IndexWriter.java.rej
Would it be possible for you to regenerate the patch against
IndexWriter in HEAD?
Also, I noticed ^Ms in the patch, but I can take care of those
easily (dos2unix).
Finally, I noticed in 2-3 places that the simple logging via
"infoStream" variable was removed, for example:
- if (infoStream != null) infoStream.print("merging segments");
Perhaps this was just an oversight?
Looking forward to the new patch. Thanks!
Supporting deleteDocuments in IndexWriter (Code and Performance
Results Provided)
---------------------------------------------------------------------
------------
Key: LUCENE-565
URL: http://issues.apache.org/jira/browse/LUCENE-565
Project: Lucene - Java
Type: Bug
Components: Index
Reporter: Ning Li
Attachments: IndexWriter.java, IndexWriter.patch,
TestWriterDelete.java
Today, applications have to open/close an IndexWriter and open/
close an
IndexReader directly or indirectly (via IndexModifier) in order to
handle a
mix of inserts and deletes. This performs well when inserts and
deletes
come in fairly large batches. However, the performance can degrade
dramatically when inserts and deletes are interleaved in small
batches.
This is 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.
We would like to propose a small API change to eliminate this
problem. We
are aware that this kind change has come up in discusions before. See
http://www.gossamer-threads.com/lists/lucene/java-dev/23049?
search_string=indexwriter%20delete;#23049
. The difference this time is that we have implemented the change and
tested its performance, as described below.
API Changes
-----------
We propose adding a "deleteDocuments(Term term)" method to
IndexWriter.
Using this method, inserts and deletes can be interleaved using
the same
IndexWriter.
Note that, with this change it would be very easy to add another
method to
IndexWriter for updating documents, allowing applications to avoid a
separate delete and insert to update a document.
Also note that this change can co-exist with the existing APIs for
deleting
documents using an IndexReader. But if our proposal is accepted,
we think
those APIs should probably be deprecated.
Coding Changes
--------------
Coding changes are localized to IndexWriter. Internally, the new
deleteDocuments() method works by buffering the terms to be deleted.
Deletes are deferred until the ramDirectory is flushed to disk,
either
because it becomes full or because the IndexWriter is closed.
Using Java
synchronization, care is taken to ensure that an interleaved
sequence of
inserts and deletes for the same document are properly serialized.
We have attached a modified version of IndexWriter in Release
1.9.1 with
these changes. Only a few hundred lines of coding changes are
needed. All
changes are commented by "CHANGE". We have also attached a
modified version
of an example from Chapter 2.2 of Lucene in Action.
Performance Results
-------------------
To test the performance our proposed changes, we ran some
experiments using
the TREC WT 10G dataset. The experiments were run on a dual 2.4
Ghz Intel
Xeon server running Linux. The disk storage was configured as
RAID0 array
with 5 drives. Before indexes were built, the input documents were
parsed
to remove the HTML from them (i.e., only the text was indexed).
This was
done to minimize the impact of parsing on performance. A simple
WhitespaceAnalyzer was used during index build.
We experimented with three workloads:
- Insert only. 1.6M documents were inserted and the final
index size was 2.3GB.
- Insert/delete (big batches). The same documents were
inserted, but 25% were deleted. 1000 documents were
deleted for every 4000 inserted.
- Insert/delete (small batches). In this case, 5 documents
were deleted for every 20 inserted.
current current new
Workload IndexWriter IndexModifier
IndexWriter
---------------------------------------------------------------------
--
Insert only 116 min 119 min 116 min
Insert/delete (big batches) -- 135 min 125 min
Insert/delete (small batches) -- 338 min 134 min
As the experiments show, with the proposed changes, the performance
improved by 60% when inserts and deletes were interleaved in small
batches.
Regards,
Ning
Ning Li
Search Technologies
IBM Almaden Research Center
650 Harry Road
San Jose, CA 95120
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