Improve PartitionMergeSpec.
Improve PartitionMergeSpec.

jedesah/Quasar,drostron/quasar,drostron/quasar,slamdata/slamengine,quasar-analytics/quasar,djspiewak/quasar,jedesah/Quasar,jedesah/Quasar,drostron/quasar,slamdata/slamengine,quasar-analytics/quasar,jedesah/Quasar,drostron/quasar,slamdata/slamengine,quasar-analytics/quasar,slamdata/quasar,quasar-analytics/quasar