Fix to_iso8601 to use Z for UTC (facebookincubator#11279)

Summary:

Presto's to_iso8601 UDF uses JODA's default ISODateTimeFormat.dateTime()
formatter which uses the string 'Z' in place of the time zone offset if the time zone is
UTC.
https://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime--

Internally JODA's DateTimeFormatter does this by taking an optional hard coded
string to use for the time zone offset if it's zero. I added something similar to Velox's
DateTimeFormatter.format and setting it in the to_iso8601 implementation.

I checked and other Presto UDFs that format TimestampWithTimeZones as strings,
e.g. format_datetime, do not use this option, so they do not need to be updated.

Reviewed By: bikramSingh91

Differential Revision: D64488962

velox/functions/lib/DateTimeFormatter.cpp

@@ -1067,7 +1067,8 @@ int32_t DateTimeFormatter::format(
     const tz::TimeZone* timezone,
     const uint32_t maxResultSize,
     char* result,
-    bool allowOverflow) const {
+    bool allowOverflow,
+    const std::optional<std::string>& zeroOffsetText) const {
   int64_t offset = 0;
   Timestamp t = timestamp;
   if (timezone != nullptr) {
@@ -1300,6 +1301,13 @@ int32_t DateTimeFormatter::format(
                 getSpecifierName(token.pattern.specifier),
                 token.pattern.minRepresentDigits);
           }
+
+          if (offset == 0 && zeroOffsetText.has_value()) {
+            std::memcpy(result, zeroOffsetText->data(), zeroOffsetText->size());
+            result += zeroOffsetText->size();
+            break;
+          }
+
           result += appendTimezoneOffset(offset, result);
           break;
         }

velox/functions/lib/DateTimeFormatter.h

@@ -206,7 +206,8 @@ class DateTimeFormatter {
       const tz::TimeZone* timezone,
       const uint32_t maxResultSize,
       char* result,
-      bool allowOverflow = false) const;
+      bool allowOverflow = false,
+      const std::optional<std::string>& zeroOffsetText = std::nullopt) const;
 
  private:
   std::unique_ptr<char[]> literalBuf_;

velox/functions/prestosql/DateTimeFunctions.h

@@ -1798,8 +1798,8 @@ struct ToISO8601Function {
       out_type<Varchar>& result) const {
     const auto maxResultSize = formatter_->maxResultSize(timeZone);
     result.reserve(maxResultSize);
-    const auto resultSize =
-        formatter_->format(timestamp, timeZone, maxResultSize, result.data());
+    const auto resultSize = formatter_->format(
+        timestamp, timeZone, maxResultSize, result.data(), false, "Z");
     result.resize(resultSize);
   }
 

velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp

@@ -4512,11 +4512,11 @@ TEST_F(DateTimeFunctionsTest, toISO8601Timestamp) {
         "to_iso8601(c0)", std::make_optional(parseTimestamp(timestamp)));
   };
   disableAdjustTimestampToTimezone();
-  EXPECT_EQ("2024-11-01T10:00:00.000+00:00", toIso("2024-11-01 10:00"));
-  EXPECT_EQ("2024-11-04T10:00:00.000+00:00", toIso("2024-11-04 10:00"));
-  EXPECT_EQ("2024-11-04T15:05:34.100+00:00", toIso("2024-11-04 15:05:34.1"));
-  EXPECT_EQ("2024-11-04T15:05:34.123+00:00", toIso("2024-11-04 15:05:34.123"));
-  EXPECT_EQ("0022-11-01T10:00:00.000+00:00", toIso("22-11-01 10:00"));
+  EXPECT_EQ("2024-11-01T10:00:00.000Z", toIso("2024-11-01 10:00"));
+  EXPECT_EQ("2024-11-04T10:00:00.000Z", toIso("2024-11-04 10:00"));
+  EXPECT_EQ("2024-11-04T15:05:34.100Z", toIso("2024-11-04 15:05:34.1"));
+  EXPECT_EQ("2024-11-04T15:05:34.123Z", toIso("2024-11-04 15:05:34.123"));
+  EXPECT_EQ("0022-11-01T10:00:00.000Z", toIso("22-11-01 10:00"));
 
   setQueryTimeZone("America/Los_Angeles");
   EXPECT_EQ("2024-11-01T03:00:00.000-07:00", toIso("2024-11-01 10:00"));
@@ -4562,6 +4562,10 @@ TEST_F(DateTimeFunctionsTest, toISO8601TimestampWithTimezone) {
   EXPECT_EQ(
       "0022-11-01T10:00:00.000+05:41:16",
       toIso("22-11-01 10:00", "Asia/Kathmandu"));
+
+  EXPECT_EQ("2024-11-01T10:00:00.000Z", toIso("2024-11-01 10:00", "UTC"));
+  EXPECT_EQ("2024-11-04T10:00:45.120Z", toIso("2024-11-04 10:00:45.12", "UTC"));
+  EXPECT_EQ("0022-11-01T10:00:00.000Z", toIso("22-11-01 10:00", "UTC"));
 }
 
 TEST_F(DateTimeFunctionsTest, atTimezoneTest) {