Closing a session do not release memory

[david-stephan]

If I open a session for instance connecting to the collector's database and query some data. As expected the data required to display and filter the tree view, events... are stored in memory.
If a perform a second query, the memory is properly released before fetching the new data.
However If I close this session and reopen a new one, the data stay in memory and accumulate.
If I repeat that a few time I will eventually get an out of memory error.