simpleScalarFilterToParseTree() performs a dynamic allocation
of a ParseTree object, but this memory is never freed later.
We now keep track of this allocation and perform the delete
in ~CSEP/CSEP::unserialize() after the query finishes.
MCOL-894 Add default values in Compare and CSEP ctors to activate UTF-8 sorting
properly.
MCOL-894 Unit tests to build a framework for a new parallel sorting.
MCOL-894 Finished with parallel workers invocation.
The implementation lacks final aggregation step.
MCOL-894 TupleAnnexStep's init and destructor are now parallel execution aware.
Implemented final merging step for parallel execution finalizeParallelOrderBy().
Templated unit test to use it with arbitrary number of rows, threads.
Reuse LimitedOrderBy in the final step
MCOL-894 Cleaned up finalizeParallelOrderBy.
MCOL-894 Add and propagate thread variable that controls a number of threads.
Optimized comparators used for sorting and add corresponding UTs.
Refactored TupleAnnexStep::finalizeParallelOrderByDistinct.
Parallel sorting methods now preallocates memory in batches.
MCOL-894 Fixed comparator for StringCompare.
