[redland-dev] Possible problem in "tree" storage implementation. librdf_avltree_delete()

[Aymeric Barthe]

We have a tool using librdf and we recently switched to the experimental
"tree" storage. We have a small rdf database of roughly 200kb that fits
in memory. We make a lot of SPARQL requests and some changes
(add/delete) in the db. We found out that "tree" provides a real
performance boost for our application.

However we have encountered some crashes. I can't provide you with a
sample of code that can reproduce the crash yet, but after investigation
I suspect the librdf_avltree_delete().

The problem is the following. After calling librdf_avltree_delete() (via
librdf_model_remove_statement()) we end up with a corrupted (SPO) tree
in memory. What happens is that the parent of some child node (right or
left) points to an incorrect memory location. 

Basically we end up with (node->left->parent != node) or
(node->right->parent != node).

Have any of you experienced similar troubles with the avl tree storage?
Is this a known problem? If not, I hope to pursue my investigation and
possibly provide a patch on next week. Any idea/advice of how I could
approach the issue? 

Kind Regards,

Aymeric Barthe 
Thomson Reuters



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