Hi,
I tried to do what suggested to me, adopted the document and released the
parser, but it didn't help much to reduce the memory consumption.
So I made the following trials which didn't succeed too much. Could you please
help me figure out what I'm doing wrong and how should I do it correctly?
1. I tried to import the root node and release the document.
After the call to DOMDocumentImpl::release() some memory is released,
but:
a. not all memory (used memory is more than what was before starting to
use xerces)
b. after releasing the memory, I couldn't use the root node anymore
since it's corrupted after the document's released.
2. I saw that there is an adoptNode() function, so I tried to use it- adopt the
root node and than release
the document.
However, when trying this I got an exception, so I looked at the source
code and found that in xerces 2.8.0 adoptNode() has the following
implementation:
DOMNode* DOMDocumentImpl::adoptNode(DOMNode*) {
throw DOMException(DOMException::NOT_SUPPORTED_ERR, 0, getMemoryManager());
return 0;
}
I looked at the source code of xerces 3.0.1 which has different implementation
to that function, however, it didn't seem to do what I expected it to do
(bottom line is, that using it didn't help either)
- Eventually, I don't know how can I release the memory allocated by xerces....
Another issue that I realized is: I saw that we use (quite a lot) the function:
DOMNodeList *DOMElementImpl::getElementsByTagName(const XMLCh *tagname) const
I wondered when (and by whom) should the returned DOMNodeList* be deleted, I
saw an answer regarding this issue in the following link:
http://www.mail-archive.com/[email protected]/msg02511.html
but didn't understand what is the meaning of: Memory for any returned object
... are owned by implementation - whose implementation?
I think that releasing these lists after we used finished using them might help
us as well (I saw that the fNodeListPool is cleaned up when the document is
deleted, but it is not explicitly deleted in any place I could find)
Thanks in advance,
Drora Altman
-----Original Message-----
From: David Bertoni [mailto:[email protected]]
Sent: Wednesday, July 15, 2009 9:03 PM
To: [email protected]
Subject: Re: Right usage of xerces
Altman, Drora wrote:
> Hi,
>
> We have a project that uses xerces (2.8.0) in order to parse xml files. We
> allocate the data as a DOM object in memory and work on it (adding/deleting
> nodes).
> The xml are quiet big.
>
> It seems that we miss something in the right usage of xerces, since the
> application consumes a lot of memory and it does not seem to be released
> properly.
> During our investigation of the code, I realized that the code uses the
> importNode function, which, as far as I understand, allocates the memory.
> This brings me to the following questions:
>
> 1. What's the difference between the importNode() & cloneNode() functions?
importNode() essentially clones a node from another document so you can add it
to the target document.
> 2. How can we actually delete the memory allocated by import\cloneNode if we
> delete this node afterwards?
All of the memory for nodes is allocated from a pool owned by the document
instance. There is no way to recover memory for individual nodes.
> 3. What are your general recommendations, regarding cleanup memory at the end
> of the usage of xerces?
If your usage model involves creating and releasing lots of nodes, you might
want to consider "compacting" a document by cloning the entire document node
and releasing the original document. If you created the original document using
a parser, remember the document instance itself is owned by the parser, unless
you call adoptDocument() on the parser instance.
Dave
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