From 1714c45aa146f27b3df20dfe692777c2765e71d6 Mon Sep 17 00:00:00 2001
From: Gian Merlino <gianmerlino@gmail.com>
Date: Wed, 6 Dec 2023 01:39:59 -0800
Subject: [PATCH] Fix NullFilter getDimensionRangeSet. (#15500)

It wasn't checking the column name, so it would return a domain regardless
of the input column. This means that null filters on data sources with range
partitioning would lead to excessive pruning of segments, and therefore
missing results.
---
 .../apache/druid/query/filter/NullFilter.java    |  4 ++++
 .../druid/segment/filter/NullFilterTests.java    | 16 ++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/processing/src/main/java/org/apache/druid/query/filter/NullFilter.java b/processing/src/main/java/org/apache/druid/query/filter/NullFilter.java
index 14bdb6f4185e..da737bdce890 100644
--- a/processing/src/main/java/org/apache/druid/query/filter/NullFilter.java
+++ b/processing/src/main/java/org/apache/druid/query/filter/NullFilter.java
@@ -114,6 +114,10 @@ public Filter toFilter()
   @Override
   public RangeSet<String> getDimensionRangeSet(String dimension)
   {
+    if (!Objects.equals(getColumn(), dimension)) {
+      return null;
+    }
+
     RangeSet<String> retSet = TreeRangeSet.create();
     // Nulls are less than empty String in segments
     retSet.add(Range.lessThan(""));
diff --git a/processing/src/test/java/org/apache/druid/segment/filter/NullFilterTests.java b/processing/src/test/java/org/apache/druid/segment/filter/NullFilterTests.java
index b123ead53a54..084c1c24c2bf 100644
--- a/processing/src/test/java/org/apache/druid/segment/filter/NullFilterTests.java
+++ b/processing/src/test/java/org/apache/druid/segment/filter/NullFilterTests.java
@@ -23,6 +23,8 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Range;
+import com.google.common.collect.TreeRangeSet;
 import nl.jqno.equalsverifier.EqualsVerifier;
 import org.apache.druid.common.config.NullHandling;
 import org.apache.druid.jackson.DefaultObjectMapper;
@@ -41,6 +43,7 @@
 
 import java.io.Closeable;
 import java.util.Arrays;
+import java.util.Collections;
 
 @RunWith(Enclosed.class)
 public class NullFilterTests
@@ -310,6 +313,19 @@ public void testArrays()
 
   public static class NullFilterNonParameterizedTest
   {
+    @Test
+    public void testGetDimensionRangeSet()
+    {
+      final NullFilter filter = new NullFilter("x", null);
+
+      Assert.assertEquals(
+          TreeRangeSet.create(Collections.singleton(Range.lessThan(""))),
+          filter.getDimensionRangeSet("x")
+      );
+
+      Assert.assertNull(filter.getDimensionRangeSet("y"));
+    }
+
     @Test
     public void testSerde() throws JsonProcessingException
     {