feat(iceberg): Add timestamptz_ns function

Author: Joe-Abraham

velox/functions/iceberg/DateTimeFunctions.cpp

@@ -100,6 +100,19 @@ struct TimestampNsFunction {
   }
 };
 
+// timestamptz_ns(input) -> nanoseconds from 1970-01-01 00:00:00.000000000 UTC
+// Input is timestamp with timezone.
+template <typename TExec>
+struct TimestamptzNsFunction {
+  VELOX_DEFINE_FUNCTION_TYPES(TExec);
+
+  FOLLY_ALWAYS_INLINE void call(
+      int64_t& result,
+      const arg_type<Timestamp>& timestamp) {
+    result = epochNanos(timestamp);
+  }
+};
+
 void registerDateTimeFunctions(const std::string& prefix) {
   registerFunction<YearsFunction, int32_t, Timestamp>({prefix + "years"});
   registerFunction<YearsFunction, int32_t, Date>({prefix + "years"});
@@ -110,6 +123,8 @@ void registerDateTimeFunctions(const std::string& prefix) {
   registerFunction<HoursFunction, int32_t, Timestamp>({prefix + "hours"});
   registerFunction<TimestampNsFunction, int64_t, Timestamp>(
       {prefix + "timestamp_ns"});
+  registerFunction<TimestamptzNsFunction, int64_t, Timestamp>(
+      {prefix + "timestamptz_ns"});
 }
 
 } // namespace facebook::velox::functions::iceberg

velox/functions/iceberg/tests/DateTimeFunctionsTest.cpp

@@ -104,5 +104,26 @@ TEST_F(DateTimeFunctionsTest, timestampNs) {
   EXPECT_EQ(-1000000000L, timestampNs("1969-12-31 23:59:59.000000"));
 }
 
+TEST_F(DateTimeFunctionsTest, timestamptzNs) {
+  const auto timestamptzNs = [&](const std::string& ts) {
+    return evaluateOnce<int64_t>(
+        "timestamptz_ns(c0)",
+        std::make_optional<Timestamp>(parseTimestamp(ts)));
+  };
+
+  // 1970-01-01 00:00:00.000000000 UTC should be 0
+  EXPECT_EQ(0, timestamptzNs("1970-01-01 00:00:00.000000"));
+
+  // 2017-12-01 10:12:55.038194 is 1512123175038194000 nanoseconds from
+  // 1970-01-01 UTC
+  EXPECT_EQ(1512123175038194000L, timestamptzNs("2017-12-01 10:12:55.038194"));
+
+  // 1970-01-01 00:00:01.000001 is 1000001000 nanoseconds from 1970-01-01 UTC
+  EXPECT_EQ(1000001000L, timestamptzNs("1970-01-01 00:00:01.000001"));
+
+  // Timestamp before 1970 should be negative
+  EXPECT_EQ(-1000000000L, timestamptzNs("1969-12-31 23:59:59.000000"));
+}
+
 } // namespace
 } // namespace facebook::velox::functions::iceberg