[jira] [Created] (HBASE-20208) Review of SequenceIdAccounting.java

[BELUGA BEHR (JIRA)]

BELUGA BEHR created HBASE-20208:
-----------------------------------

             Summary: Review of SequenceIdAccounting.java
                 Key: HBASE-20208
                 URL: https://issues.apache.org/jira/browse/HBASE-20208
             Project: HBase
          Issue Type: Improvement
          Components: hbase
    Affects Versions: 2.0.0
            Reporter: BELUGA BEHR
         Attachments: HBASE-20208.1.patch

# Fix checkstyle warnings
# Use re-usable libraries where possible
# Improve Map Access

What got my attention on this class was:

{code}
for (Map.Entry<byte[], Long> e : sequenceids.entrySet()) {
      long oldestFlushing = Long.MAX_VALUE;
      long oldestUnflushed = Long.MAX_VALUE;
      if (flushing != null && flushing.containsKey(e.getKey())) {
        oldestFlushing = flushing.get(e.getKey());
      }
      if (unflushed != null && unflushed.containsKey(e.getKey())) {
        oldestUnflushed = unflushed.get(e.getKey());
      }
      long min = Math.min(oldestFlushing, oldestUnflushed);
      if (min <= e.getValue()) {
        return false;
      }
{code}

Here, the two maps are calling _containsKey_ and then _get_.  It is also 
calling {{e.getKey()}} repeatedly.

I propose changing this so that {{e.getKey()}} is only called once and instead 
of looking up an entry with _containsKey_ and then a _get_, simply use _get_ 
once and check for a 'null' value to check for existence.  It saves two trips 
through the Map Collection on each loop.



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