From 6a996adf166171363b898531dc7361086385b836 Mon Sep 17 00:00:00 2001
From: Abhishek Agarwal <1477457+abhishekagarwal87@users.noreply.github.com>
Date: Tue, 25 Jul 2023 14:07:55 +0530
Subject: [PATCH] Fix the bug in string last vector aggregation

---
 .../last/StringLastVectorAggregator.java      |  5 ++++-
 .../last/StringLastVectorAggregatorTest.java  | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/processing/src/main/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregator.java b/processing/src/main/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregator.java
index 045360ba6167..f10584a2c748 100644
--- a/processing/src/main/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregator.java
+++ b/processing/src/main/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregator.java
@@ -42,7 +42,7 @@ public class StringLastVectorAggregator implements VectorAggregator
   protected long lastTime;
 
   public StringLastVectorAggregator(
-      final BaseLongVectorValueSelector timeSelector,
+      @Nullable final BaseLongVectorValueSelector timeSelector,
       final VectorObjectSelector valueSelector,
       final int maxStringBytes
   )
@@ -124,6 +124,9 @@ public void aggregate(
       int positionOffset
   )
   {
+    if (timeSelector == null) {
+      return;
+    }
     long[] timeVector = timeSelector.getLongVector();
     Object[] objectsWhichMightBeStrings = valueSelector.getObjectVector();
 
diff --git a/processing/src/test/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregatorTest.java b/processing/src/test/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregatorTest.java
index 428ff3e3742f..6e5c0275107b 100644
--- a/processing/src/test/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregatorTest.java
+++ b/processing/src/test/java/org/apache/druid/query/aggregation/last/StringLastVectorAggregatorTest.java
@@ -129,6 +129,25 @@ public void aggregate()
     Assert.assertEquals(VALUES[3], result.rhs);
   }
 
+  @Test
+  public void aggregateNoOp()
+  {
+    // Test that aggregates run just fine when the input field does not exist
+    StringLastVectorAggregator aggregator = new StringLastVectorAggregator(null, selector, 10);
+    aggregator.aggregate(buf, 0, 0, VALUES.length);
+  }
+
+  @Test
+  public void aggregateBatchNoOp()
+  {
+    // Test that aggregates run just fine when the input field does not exist
+    StringLastVectorAggregator aggregator = new StringLastVectorAggregator(null, selector, 10);
+    int[] positions = new int[]{0, 43, 70};
+    int positionOffset = 2;
+    clearBufferForPositions(positionOffset, positions);
+    aggregator.aggregate(buf, 3, positions, null, positionOffset);
+  }
+
   @Test
   public void aggregateBatchWithoutRows()
   {