Gregory JEVARDAT created OPENJPA-2814:
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Summary: Memory Leak in ForeignKey class
Key: OPENJPA-2814
URL: https://issues.apache.org/jira/browse/OPENJPA-2814
Project: OpenJPA
Issue Type: Bug
Components: jdbc
Affects Versions: 3.0.0
Reporter: Gregory JEVARDAT
I analyzed and solved a memory leak in the ForeignKey class.
Context is that I run a batch application running as a service and reading
billions of entities.
I realised that ForeignKey classes were accumulating in the heap after each
query reading these entities and were never garbaged leading after few hundreds
of millions of read and hours of processing to full heap.
After profiling and debugging the leak is coming from the
ForeignKey.join(Column local,Column toPOK) method, more precisely in the line
574 were
local.addConstraint(this) is performed.
Here the ForeignKeys are added to a Set in the Column class.
Issue is that the ForeignKey has no equals and hashcode implemented resulting
in what it seems to me logically equivalent ForeignKeys added and accumulating
indefinitely in the map of Columns. Indeed, for whatever reason a new
ForeignKey class is created each time (which also sounds weird) at
RelationFieldStrategy.createTranslatingForeignKey method
Solution: after implementing equals and hashcode in ForeignKey and Constraint
class, the application works smoothly and the memory leak is gone. Maybe it
should be done for DBIdentifier also ?
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