mayankshriv commented on a change in pull request #5419:
URL: https://github.com/apache/incubator-pinot/pull/5419#discussion_r428218159
##########
File path:
pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/groupby/DictionaryBasedGroupKeyGenerator.java
##########
@@ -106,18 +108,26 @@ public DictionaryBasedGroupKeyGenerator(TransformOperator
transformOperator,
_isSingleValueColumn[i] =
transformOperator.getResultMetadata(groupByExpression).isSingleValue();
}
-
if (longOverflow) {
_globalGroupIdUpperBound = numGroupsLimit;
- _rawKeyHolder = new ArrayMapBasedHolder(_globalGroupIdUpperBound);
+ if
(!mapBasedRawKeyHolders.containsKey(ArrayMapBasedHolder.class.getName())) {
+ mapBasedRawKeyHolders.put(ArrayMapBasedHolder.class.getName(), new
ArrayMapBasedHolder(_globalGroupIdUpperBound).getInternal());
Review comment:
I think initializing to `_globalGroupIdUpperBound` got introduced in
#5291. For many cases with multiple group by columns (high cardinality and/or
MV columns) this number can be huge. Unclear to me if making this thread-local
will protect against such cases that may require allocating huge chunk of
memory upfornt.
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