Keyong Zhou

Fix aggregate flags in initializeGlobalAggregation

5

`GroupingSet::initializeGlobalAggregation` updates `accumulatorFlagsOffset` for each valid aggregate in `aggregates_`, `sortedAggregations_` and `distinctAggregations_`, but the calculation of bytes of the flags only considers `aggregates_`, which leads to failure of the following...

[CELEBORN-1378] Call PartitionDataWriter#flush() before submitting to commitThreadPool

2

### What changes were proposed in this pull request? There are high commit files latency in some production environments. This PR triggers flush before calling close to avoid waiting in...