Hi, Folks. Thanks, Ruben, for your help. It let me get a ways down the
road.
The problem is the the heap is filling up when I am doing a
lucene.TermQuery. What I am trying to accomplish is to get the terms in
one
field of each document and their frequency in the document. A code
snippet
is attached below. It yields the results I want.
I managed to get a small enough heap dump into jhat. Now I could use
some
help understanding what I have found and some help figuring out what to
do
about it. I am a noobi at understanding the details of Lucene,
pyLucene,
and Java debugging.
If I understand correctly, the heap is filling up because it is keeping
instances of objects around after there is no longer any need for them.
I
thought that it might be the case that Python was somehow keeping them
around, but that does not seem to be the case (true?).
From jhat, I got a class instance histogram:
290163 instances <http://192.168.1.155:7000/instances/0x7fbf693bb990> of
class org.apache.lucene.index.TermInfo
<http://192.168.1.155:7000/class/0x7fbf693bb990>
289988 instances <http://192.168.1.155:7000/instances/0x7fbf69412d80> of
class org.apache.lucene.index.Term
<http://192.168.1.155:7000/class/0x7fbf69412d80>
1976 instances <http://192.168.1.155:7000/instances/0x7fbf693f1300> of
class
org.apache.lucene.index.FieldInfo
<http://192.168.1.155:7000/class/0x7fbf693f1300>
1976 instances <http://192.168.1.155:7000/instances/0x7fbf6940a1a8> of
class
org.apache.lucene.index.SegmentReader$Norm
<http://192.168.1.155:7000/class/0x7fbf6940a1a8>
1081 instances <http://192.168.1.155:7000/instances/0x7fbf6928d460> of
class
org.apache.lucene.store.FSDirectory$FSIndexInput
<http://192.168.1.155:7000/class/0x7fbf6928d460>
1048 instances <http://192.168.1.155:7000/instances/0x7fbf693ef958> of
class
org.apache.lucene.index.CompoundFileReader$CSIndexInput
<http://192.168.1.155:7000/class/0x7fbf693ef958>
540 instances <http://192.168.1.155:7000/instances/0x7fbf69400510> of
class
org.apache.lucene.index.TermBuffer
<http://192.168.1.155:7000/class/0x7fbf69400510>
540 instances <http://192.168.1.155:7000/instances/0x7fbf694011c8> of
class
org.apache.lucene.util.UnicodeUtil$UTF16Result
<http://192.168.1.155:7000/class/0x7fbf694011c8>
540 instances <http://192.168.1.155:7000/instances/0x7fbf693bc168> of
class
org.apache.lucene.util.UnicodeUtil$UTF8Result
<http://192.168.1.155:7000/class/0x7fbf693bc168>
...
There are way too many instance of index.TermInfo and index.indexTerm.
So,
I tracked down some instances and looked for rootset references. There
were
none. If I understand correctly, this instance should be garbage
collected
if there are no rootset references. True?
Here's an example from jhat:
Rootset references to org.apache.lucene.index.termi...@0x7fbf6e3f8218
(includes weak refs)
References to org.apache.lucene.index.termi...@0x7fbf6e3f8218 (40
bytes)
Other queries
Exclude weak refs
---
There is at least one reference to the object, it is an element in an
array,
but the array does not have rootset references either.
Am I misinterpreting these results? In any case, what can I do about
getting rid of these? Is it a bug in this version of Lucene? Is there
a
known fix? I think that I should be able to do an unlimited number of
queries without filling up the heap.
I am using pyLucene version 2.4.
Thanks for your help.
Herb
-------------------------------
Code snippet:
reader = self.index.getReader()
lReader = reader.get()
searcher = self.index.getSearcher()
lSearcher = searcher.get()
query = lucene.TermQuery(lucene.Term(OTDocument.UID_FIELD_ID,
uid))
hits = list(lSearcher.search(query))
if hits:
hit = lucene.Hit.cast_(hits[0])
tfvs = lReader.getTermFreqVectors(hit.id)
if tfvs is not None: # this happens if the vector is not
stored
for tfv in tfvs: # There's one for each field that has a
TermFreqVector
tfvP = lucene.TermFreqVector.cast_(tfv)
if returnAllFields or tfvP.field in termFields: # add
only
asked fields
tFields[tfvP.field] = dict([(t,f) for (t,f) in
zip(tfvP.getTerms(),tfvP.getTermFrequencies()) if f >=minFreq])
else:
# This shouldn't happen, but we just log the error and march
on
self.log.error("Unable to fetch doc %s from index"%(uid))
## if self.opCount % 1000 == 0:
## print lucene.JCCEnv._dumpRefs(classes=True).items()
#http://lists.osafoundation.org/pipermail/pylucene-dev/2008-January/002171.html
## self.opCount += 1
lReader.close()
lSearcher.close()
retFields = copy.deepcopy(tFields) #return a copy of tFields to
free
up references to it and its contents
Herbert Roitblat wrote:
Hi, folks.
I am using PyLucene and doing a lot of get tokens. lucene.py reports
version 2.4.0. It is rpath linux with 8GB of memory. Python is 2.4.
I'm not sure what the maxheap is, I think that it is maxheap='2048m'.
I
think that it's running in a 64 bit environment.
It indexes a set of 116,000 documents just fine.
Then I need to get the tokens from these documents and near the end, I
run
into:
java.lang.OutOfMemoryError: GC overhead limit exceeded
If I wait a bit and ask again for the same document's tokens, I can get
them, but it then is somewhat likely to post the same error on a
certain
number of other documents. I can handle these errors and ask again.
I have read that this error message means that the heap is getting
filled
up and garbage collection removes only a small amount of it. Since all
I am
doing is retrieving, why should the heap be filling up? I restarted
the
system before starting the retrieval.
My guess is that there is some small memory leak because memory
assigned
to my python program grows slowly as I request more document tokens.
Since
I'm not intending to change anything in either my python program or in
Lucene, any growth is unintentional. I'm just getting tokens.
we use lucene.TermQuery as the query object to get the terms.
I cannot share the documents nor the application code, but I might be
able
to provide snippets.
One last piece of information, the time needed to retrieve documents
slows
throughout the process. In the beginning I was getting about 10
documents
per second. Towards the end, it is down to about 5 with about 5 second
pauses from time to time, perhaps due to garbage collection?
Any idea of why the heap is filling up and what I can do about it?
Thanks,
Herb
