The bug:
There was a MemPool in AnalyticEvalNode with a dual purpose:
(1) Allocate temporary tuples.
(2) Back the FunctionContexts of the aggregate function evaluators.
FunctionContexts use FreePools to do their own memory management using a
pointer-based structure that is stored in the memory blocks themselves.
When calling AnalyticEvalNode::Reset() we reset that mem pool backing
that pointer-based structure. Those pointers were then clobbered by
subsequent allocations (and writes) for temporary tuples, ultimately
resulting in the FreePool incorrectly reporting a double free
while doing a Finalize() of an aggregate function.
The fix:
While there are several other ways to address this issue, I chose to
use a different MemPool for the FunctionContexts because that seemed
to be the most sane and minimally invasive fix. That MemPool is not
reset during AnalyticEvalNode::Reset() because the memory is
ultimately managed by the FreePools of the FunctionContexts.
Change-Id: I42fd60785d3c6dec93436cd9ca64de58d1b15c7e
Reviewed-on: http://gerrit.cloudera.org:8080/857
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: Internal Jenkins
ef29c976df