Major Description
The big memory operators in Trafodion are HashJoin, HashGroupBy and Sort. Trafodion deploys multiple executor server processes (ESPs) to execute a query via its data flow architecture. Each ESPs can have an instance of this BMO operator. Currently, each instance of this operator can potentially have memory quota of 800 MB assigned to do its BMO operation. However, the memory allocation is usually limited by the memory pressure when this BMO attempts to allocate memory within the assigned quota. The assignment doesn't depend upon the estimation of memory needed by this operation.
Improvement needed in BMO memory assignment are:
1. Limit the memory quota assignment for these BMO operations per node
2. Memory quota assigned taking into consideration estimated memory needed at every operator.
3. Ensure that the BMO gets the minimum memory needed at least to function smoothly
