Add tests for casting UNKNOWN type to any other type (#6996)

Summary: Pull Request resolved: #6996 Reviewed By: xiaoxmeng Differential Revision: D54201176 Pulled By: mbasmanova fbshipit-source-id: 4059e775b6258046d7c012675ea75f7799cafa59
facebookincubator · Feb 27, 2024 · 62b8cfd · 62b8cfd
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diff --git a/velox/docs/functions/spark/conversion.rst b/velox/docs/functions/spark/conversion.rst
@@ -2,6 +2,8 @@
 Conversion Functions
 ====================
 
+Casting from UNKNOWN type to all other scalar types is supported, e.g., cast(NULL as int).
+
 Cast to Integral Types
 ----------------------
 

diff --git a/velox/expression/tests/CastExprTest.cpp b/velox/expression/tests/CastExprTest.cpp
@@ -371,6 +371,33 @@ TEST_F(CastExprTest, basics) {
       {"1.888", "2.5", "3.6", "100.44", "-100.101", "1", "-2"});
 }
 
+TEST_F(CastExprTest, fromUnknownType) {
+  testCast<UnknownValue, int8_t>(
+      "tinyint", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, int16_t>(
+      "smallint", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, int32_t>(
+      "int", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, int64_t>(
+      "bigint", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, float>(
+      "float", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, double>(
+      "double", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, std::string>(
+      "string", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, bool>(
+      "boolean", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, Timestamp>(
+      "timestamp", {std::nullopt, std::nullopt}, {std::nullopt, std::nullopt});
+  testCast<UnknownValue, int32_t>(
+      "date",
+      {std::nullopt, std::nullopt},
+      {std::nullopt, std::nullopt},
+      UNKNOWN(),
+      DATE());
+}
+
 TEST_F(CastExprTest, realAndDoubleToString) {
   setLegacyCast(false);
   testCast<double, std::string>(

diff --git a/velox/vector/tests/utils/VectorMakerStats.h b/velox/vector/tests/utils/VectorMakerStats.h
@@ -86,6 +86,27 @@ class VectorMakerStats {
   std::unordered_set<T> distinctSet_;
 };
 
+template <>
+class VectorMakerStats<UnknownValue> {
+ public:
+  void addElement(const UnknownValue& val) {
+    VELOX_UNREACHABLE();
+  }
+
+  size_t distinctCount() const {
+    return 1;
+  }
+
+  SimpleVectorStats<UnknownValue> asSimpleVectorStats() {
+    return {min, max};
+  }
+
+  std::optional<UnknownValue> min;
+  std::optional<UnknownValue> max;
+  size_t nullCount{0};
+  bool isSorted{false};
+};
+
 // Generates VectorMakerStats for a given vector of nullable elements.
 template <typename T>
 VectorMakerStats<EvalType<T>> genVectorMakerStats(