feat(function): Add Spark dayname function (facebookincubator#15957)

Summary:
Implements the `dayname()` function for Spark SQL compatibility that returns the three-letter abbreviated day name (Sun, Mon, Tue, Wed, Thu, Fri, Sat) from a given date.

Pull Request resolved: facebookincubator#15957

Reviewed By: xiaoxmeng

Differential Revision: D90602088

Pulled By: kevinwilfong

fbshipit-source-id: b3f41a4e05951d0b343fb4aba8857fd4a96ecde0

Author: yaooqinn

velox/docs/functions/spark/datetime.rst

@@ -106,6 +106,15 @@ These functions support TIMESTAMP and DATE input types.
         SELECT datediff('2009-07-31', '2009-07-30'); -- 1
         SELECT datediff('2009-07-30', '2009-07-31'); -- -1
 
+.. spark:function:: dayname(date) -> varchar
+
+    Returns the three-letter abbreviated day name from the given date (Sun, Mon, Tue, Wed, Thu, Fri, Sat). ::
+
+        SELECT dayname('2009-07-30'); -- 'Thu'
+        SELECT dayname('2023-08-20'); -- 'Sun'
+        SELECT dayname('2023-08-21'); -- 'Mon'
+        SELECT dayname('1582-10-15'); -- 'Fri'
+
 .. spark:function:: dayofmonth(date) -> integer
 
     Returns the day of month of the date. ::

velox/functions/sparksql/DateTimeFunctions.h

@@ -779,6 +779,40 @@ struct WeekdayFunction {
   }
 };
 
+template <typename T>
+struct DayNameFunction {
+  VELOX_DEFINE_FUNCTION_TYPES(T);
+
+  FOLLY_ALWAYS_INLINE void call(
+      out_type<Varchar>& result,
+      const arg_type<Date>& date) {
+    const auto tm = getDateTime(date);
+    switch (tm.tm_wday) {
+      case 0:
+        result.append("Sun");
+        break;
+      case 1:
+        result.append("Mon");
+        break;
+      case 2:
+        result.append("Tue");
+        break;
+      case 3:
+        result.append("Wed");
+        break;
+      case 4:
+        result.append("Thu");
+        break;
+      case 5:
+        result.append("Fri");
+        break;
+      default:
+        result.append("Sat");
+        break;
+    }
+  }
+};
+
 template <typename T>
 struct NextDayFunction {
   VELOX_DEFINE_FUNCTION_TYPES(T);

velox/functions/sparksql/registration/RegisterDatetime.cpp

@@ -65,6 +65,7 @@ void registerDatetimeFunctions(const std::string& prefix) {
   registerFunction<DateSubFunction, Date, Date, int32_t>({prefix + "date_sub"});
   registerFunction<DayFunction, int32_t, Date>(
       {prefix + "day", prefix + "dayofmonth"});
+  registerFunction<DayNameFunction, Varchar, Date>({prefix + "dayname"});
   registerFunction<DayOfYearFunction, int32_t, Date>({prefix + "dayofyear"});
   registerFunction<DayOfWeekFunction, int32_t, Date>({prefix + "dayofweek"});
   registerFunction<WeekdayFunction, int32_t, Date>({prefix + "weekday"});

velox/functions/sparksql/tests/DateTimeFunctionsTest.cpp

@@ -658,6 +658,24 @@ TEST_F(DateTimeFunctionsTest, weekdayDate) {
   EXPECT_EQ(4, weekday(parseDate("1582-10-15")));
 }
 
+TEST_F(DateTimeFunctionsTest, dayNameDate) {
+  const auto dayName = [&](std::optional<int32_t> date) {
+    return evaluateOnce<std::string>("dayname(c0)", DATE(), date);
+  };
+
+  EXPECT_EQ(std::nullopt, dayName(std::nullopt));
+  EXPECT_EQ("Thu", dayName(0)); // 1970-01-01
+  EXPECT_EQ("Sun", dayName(parseDate("2023-08-20")));
+  EXPECT_EQ("Mon", dayName(parseDate("2023-08-21")));
+  EXPECT_EQ("Tue", dayName(parseDate("2023-08-22")));
+  EXPECT_EQ("Wed", dayName(parseDate("2023-08-23")));
+  EXPECT_EQ("Thu", dayName(parseDate("2023-08-24")));
+  EXPECT_EQ("Fri", dayName(parseDate("2023-08-25")));
+  EXPECT_EQ("Sat", dayName(parseDate("2023-08-26")));
+  EXPECT_EQ(
+      "Fri", dayName(parseDate("1582-10-15"))); // Gregorian calendar start.
+}
+
 TEST_F(DateTimeFunctionsTest, dateDiffDate) {
   const auto dateDiff = [&](std::optional<int32_t> endDate,
                             std::optional<int32_t> startDate) {