From a5792a9312afcceccac676c3ed951b69c26a99a2 Mon Sep 17 00:00:00 2001
From: Laith Sakka <lsakka@fb.com>
Date: Thu, 5 Oct 2023 09:36:18 -0700
Subject: [PATCH] Fix: Explicit handle null pattern and escape in like
 function. (#6894)

Summary:


When value at constant vector is null we shall not call valueAt().
When i added a check in ConstantVector valueAt that value is not null i got other faluires
I will address them in seperate PR then add the check.

Differential Revision: D49917874
---
 velox/expression/VectorFunction.h              | 14 ++++++++++++++
 velox/functions/lib/Re2Functions.cpp           |  7 +++++++
 velox/functions/lib/tests/Re2FunctionsTest.cpp | 10 ++++++++++
 3 files changed, 31 insertions(+)

diff --git a/velox/expression/VectorFunction.h b/velox/expression/VectorFunction.h
index 57f7fc516aa19..fce97137edc58 100644
--- a/velox/expression/VectorFunction.h
+++ b/velox/expression/VectorFunction.h
@@ -152,6 +152,20 @@ class AlwaysFailingVectorFunction final : public VectorFunction {
   std::exception_ptr exceptionPtr_;
 };
 
+// This functions is used when we know a function will never be called because
+// it is default null with a literal null input value. For example like(c0,
+// null).
+class AlwaysNullDefaultNull final : public VectorFunction {
+  void apply(
+      const SelectivityVector&,
+      std::vector<VectorPtr>&,
+      const TypePtr&,
+      EvalCtx&,
+      VectorPtr&) const final {
+    VELOX_UNREACHABLE("Not expected to be called.")
+  }
+};
+
 // Factory for functions which are template generated from simple functions.
 class SimpleFunctionAdapterFactory {
  public:
diff --git a/velox/functions/lib/Re2Functions.cpp b/velox/functions/lib/Re2Functions.cpp
index 6939a62bce32a..fd160ac33e6b7 100644
--- a/velox/functions/lib/Re2Functions.cpp
+++ b/velox/functions/lib/Re2Functions.cpp
@@ -947,6 +947,9 @@ std::shared_ptr<exec::VectorFunction> makeLike(
         inputArgs[2].type->toString());
 
     auto constantEscape = escape->as<ConstantVector<StringView>>();
+    if (constantEscape->isNullAt(0)) {
+      return std::make_shared<exec::AlwaysNullDefaultNull>();
+    }
 
     try {
       VELOX_USER_CHECK_EQ(
@@ -966,6 +969,10 @@ std::shared_ptr<exec::VectorFunction> makeLike(
       "{} requires second argument to be a constant of type VARCHAR",
       name,
       inputArgs[1].type->toString());
+  if (constantPattern->isNullAt(0)) {
+    return std::make_shared<exec::AlwaysNullDefaultNull>();
+  }
+
   auto pattern = constantPattern->as<ConstantVector<StringView>>()->valueAt(0);
   if (!escapeChar) {
     PatternKind patternKind;
diff --git a/velox/functions/lib/tests/Re2FunctionsTest.cpp b/velox/functions/lib/tests/Re2FunctionsTest.cpp
index 1c640d57d612c..59a6e947d8447 100644
--- a/velox/functions/lib/tests/Re2FunctionsTest.cpp
+++ b/velox/functions/lib/tests/Re2FunctionsTest.cpp
@@ -593,6 +593,16 @@ TEST_F(Re2FunctionsTest, likePatternSuffix) {
   EXPECT_TRUE(like(input, generateString(kAnyWildcardCharacter) + input));
 }
 
+TEST_F(Re2FunctionsTest, nullConstantPatternOrEscape) {
+  // Test null pattern.
+  ASSERT_TRUE(
+      !evaluateOnce<bool>("like('a', cast (null as varchar))").has_value());
+
+  // Test null escape.
+  ASSERT_TRUE(
+      !evaluateOnce<bool>("like('a', 'a', cast(null as varchar))").has_value());
+}
+
 TEST_F(Re2FunctionsTest, likePatternAndEscape) {
   auto like = ([&](std::optional<std::string> str,
                    std::optional<std::string> pattern,