rbalamohan commented on a change in pull request #1250:
URL: https://github.com/apache/hive/pull/1250#discussion_r459811176
##########
File path:
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorGroupByOperator.java
##########
@@ -561,17 +590,25 @@ private void flush(boolean all) throws HiveException {
maxHashTblMemory/1024/1024,
gcCanary.get() == null ? "dead" : "alive"));
}
+ int avgAccess = computeAvgAccess();
/* Iterate the global (keywrapper,aggregationbuffers) map and emit
a row for each key */
Iterator<Map.Entry<KeyWrapper, VectorAggregationBufferRow>> iter =
mapKeysAggregationBuffers.entrySet().iterator();
while(iter.hasNext()) {
Map.Entry<KeyWrapper, VectorAggregationBufferRow> pair = iter.next();
+ if (!all && avgAccess >= 1) {
+ // Retain entries when access pattern is > than average access
+ if (pair.getValue().getAccessCount() > avgAccess) {
Review comment:
>> keys could retain their places for a long time because of very old
cache hits - and they will keep their place in the cache
This depends on incoming data and would be the worst case scenario similar
to earlier implementation. However, there is a corner case (again depending on
data) that large number of entries in the map exceeds the average threshold
which could prevent 10% flushing limit. Adding the reset would help preventing
this. I will create a follow up ticket on this.
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