From ea006dc72a4aea46f49470c4c55d2ca73bcf5677 Mon Sep 17 00:00:00 2001
From: Suneet Saldanha <44787917+suneet-s@users.noreply.github.com>
Date: Mon, 10 Feb 2020 14:26:10 -0800
Subject: [PATCH] Optimize TimeExtractionTopNAlgorithm (#9336)

When the time extraction Top N algorithm is looking for aggregators, it makes
2 calls to hashCode on the key. Use Map#computeIfAbsent instead so that the
hashCode is calculated only once
---
 .../druid/query/topn/TimeExtractionTopNAlgorithm.java    | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/processing/src/main/java/org/apache/druid/query/topn/TimeExtractionTopNAlgorithm.java b/processing/src/main/java/org/apache/druid/query/topn/TimeExtractionTopNAlgorithm.java
index a23518a4aa9..cee1e3ac32e 100644
--- a/processing/src/main/java/org/apache/druid/query/topn/TimeExtractionTopNAlgorithm.java
+++ b/processing/src/main/java/org/apache/druid/query/topn/TimeExtractionTopNAlgorithm.java
@@ -98,11 +98,10 @@ public class TimeExtractionTopNAlgorithm extends BaseTopNAlgorithm<int[], Map<Co
     while (!cursor.isDone()) {
       final Comparable<?> key = dimensionValueConverter.apply(dimSelector.lookupName(dimSelector.getRow().get(0)));
 
-      Aggregator[] theAggregators = aggregatesStore.get(key);
-      if (theAggregators == null) {
-        theAggregators = makeAggregators(cursor, query.getAggregatorSpecs());
-        aggregatesStore.put(key, theAggregators);
-      }
+      Aggregator[] theAggregators = aggregatesStore.computeIfAbsent(
+          key,
+          k -> makeAggregators(cursor, query.getAggregatorSpecs())
+      );
 
       for (Aggregator aggregator : theAggregators) {
         aggregator.aggregate();