mcvsubbu commented on a change in pull request #4363: When initializing mutable
dictionary, preserve 20% buffer for cardinality to reduce the chance of
re-sizing the dictionary
URL: https://github.com/apache/incubator-pinot/pull/4363#discussion_r297260962
##########
File path:
pinot-core/src/main/java/org/apache/pinot/core/indexsegment/mutable/MutableSegmentImpl.java
##########
@@ -165,9 +164,11 @@ public long getLatestIngestionTimestamp() {
dictionaryColumnSize = dataType.size();
}
String allocationContext = buildAllocationContext(_segmentName,
column, V1Constants.Dict.FILE_EXTENSION);
+ // NOTE: preserve 20% buffer for cardinality to reduce the chance of
re-sizing the dictionary
+ int estimatedCardinality = (int)
(_statsHistory.getEstimatedCardinality(column) * 1.2);
Review comment:
I think 10% should be sufficient, but then I agree that both 10 and 20
percent are arbitrary. Why not make this a per-machine config? Default can be
10, and we can play with it as needed.
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