kevinjmh opened a new pull request #3804:
URL: https://github.com/apache/carbondata/pull/3804
### Why is this PR needed?
Currently carbon uses priority queue to sort holders of sorted rows.
It first polls a holder from the heap, and adds it back if holder is not
empty.
This will cause two times heap maintainance. We can reduce half of that.
### What changes were proposed in this PR?
What will be done when poll item from priority queue is:
1. remove first item.
2. move the last item to the position of first item, siftDown the new first
item.
In the case in carbon, we can peek(without removing from heap) the first
item and get a row,
and siftDown the holder to a proper position if the holder is not empty.
### Does this PR introduce any user interface change?
- No
- Yes. (please explain the change and update document)
### Is any new testcase added?
- No
- Yes
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