From 50fac300d3ce3de943a6c0b6f559eeb546c7d70e Mon Sep 17 00:00:00 2001
From: Daniel Hunte <danielhunte@meta.com>
Date: Thu, 21 Nov 2024 15:51:13 -0800
Subject: [PATCH] fix(joins): Strengthen nullptr check for null aware hash
 joins with filters

Summary: The mayHaveNulls() method sometimes returns true when there are in fact no nulls. This change will make sure that a nullptr isn't passed to memcpy.

Differential Revision: D66333546
---
 velox/exec/HashProbe.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/velox/exec/HashProbe.cpp b/velox/exec/HashProbe.cpp
index f8a820529fe88..65200c624b78b 100644
--- a/velox/exec/HashProbe.cpp
+++ b/velox/exec/HashProbe.cpp
@@ -1212,11 +1212,12 @@ void HashProbe::prepareFilterRowsForNullAwareJoin(
     for (auto& projection : filterInputProjections_) {
       filterInputColumnDecodedVector_.decode(
           *filterInput->childAt(projection.outputChannel), filterInputRows_);
-      if (filterInputColumnDecodedVector_.mayHaveNulls()) {
+      if (const uint64_t* nulls =
+              filterInputColumnDecodedVector_.nulls(&filterInputRows_)) {
         SelectivityVector nullsInActiveRows(numRows);
         memcpy(
             nullsInActiveRows.asMutableRange().bits(),
-            filterInputColumnDecodedVector_.nulls(&filterInputRows_),
+            nulls,
             bits::nbytes(numRows));
         // All rows that are not active count as non-null here.
         bits::orWithNegatedBits(