Add support for zzzz (and beyond) in format_datetime

Summary:
This diff adds support for JODA's zzzz (or more) patterns (all equivalent) in Presto's
forma_datetime function.

This is used to format long time zone names.

Long time zone names are not available from the IANA time zone database, so we
can't use the tz library to generate these.  Fortunately, unicode provides some
utilities to generate these.

Differential Revision: D64795407

velox/functions/lib/DateTimeFormatter.cpp

@@ -16,6 +16,10 @@
 
 #include "velox/functions/lib/DateTimeFormatter.h"
 #include <folly/String.h>
+#include <unicode/locid.h>
+#include <unicode/timezone.h>
+#include <unicode/tzfmt.h>
+#include <unicode/unistr.h>
 #include <charconv>
 #include <cstring>
 #include <stdexcept>
@@ -1173,10 +1177,10 @@ uint32_t DateTimeFormatter::maxResultSize(const tz::TimeZone* timezone) const {
           // https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
           size += 5;
         } else {
-          VELOX_NYI(
-              "Date format specifier is not yet implemented: {} ({})",
-              getSpecifierName(token.pattern.specifier),
-              token.pattern.minRepresentDigits);
+          // The longest time zone long name is 40, Australian Central Western
+          // Standard Time.
+          // https://www.timeanddate.com/time/zones/
+          size += 50;
         }
 
         break;
@@ -1430,8 +1434,33 @@ int32_t DateTimeFormatter::format(
             std::memcpy(result, abbrev.data(), abbrev.length());
             result += abbrev.length();
           } else {
-            // TODO: implement full name time zone
-            VELOX_NYI("full time zone name is not yet supported");
+            UErrorCode success = U_ZERO_ERROR;
+
+            static const icu::Locale locale("en", "US");
+            static const std::unique_ptr<icu::TimeZoneFormat> format(
+                icu::TimeZoneFormat::createInstance(locale, success));
+            VELOX_USER_CHECK_NOT_NULL(format);
+
+            // Get the ICU TimeZone by name
+            const std::string& timeZoneName = timezone->name();
+            std::unique_ptr<icu::TimeZone> tz(
+                icu::TimeZone::createTimeZone(icu::UnicodeString(
+                    timeZoneName.data(), timeZoneName.length())));
+            VELOX_USER_CHECK_NOT_NULL(tz);
+
+            // Format the time zone to get the long name.
+            icu::UnicodeString longName;
+            format->format(
+                UTimeZoneFormatStyle::UTZFMT_STYLE_SPECIFIC_LONG,
+                *tz,
+                (double)timestamp.getSeconds() * 1000.0, // ICU expects a double
+                longName);
+
+            // Convert the UnicodeString back to a string and write it out
+            std::string longNameStr;
+            longName.toUTF8String(longNameStr);
+            std::memcpy(result, longNameStr.data(), longNameStr.length());
+            result += longNameStr.length();
           }
         } break;
 

velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp

@@ -3272,21 +3272,39 @@ TEST_F(DateTimeFunctionsTest, formatDateTime) {
   EXPECT_EQ("IST", formatDatetime(parseTimestamp("1970-01-01"), "zzz"));
   EXPECT_EQ("IST", formatDatetime(parseTimestamp("1970-01-01"), "zz"));
   EXPECT_EQ("IST", formatDatetime(parseTimestamp("1970-01-01"), "z"));
+  EXPECT_EQ(
+      "India Standard Time",
+      formatDatetime(parseTimestamp("1970-01-01"), "zzzz"));
+  EXPECT_EQ(
+      "India Standard Time",
+      formatDatetime(parseTimestamp("1970-01-01"), "zzzzzzzzzzzzzzzzzzzzzz"));
 
   // Test daylight savings.
   setQueryTimeZone("America/Los_Angeles");
   EXPECT_EQ("PST", formatDatetime(parseTimestamp("1970-01-01"), "z"));
   EXPECT_EQ("PDT", formatDatetime(parseTimestamp("1970-10-01"), "z"));
+  EXPECT_EQ(
+      "Pacific Standard Time",
+      formatDatetime(parseTimestamp("1970-01-01"), "zzzz"));
+  EXPECT_EQ(
+      "Pacific Daylight Time",
+      formatDatetime(parseTimestamp("1970-10-01"), "zzzz"));
 
   // Test a long abbreviation.
   setQueryTimeZone("Asia/Colombo");
   EXPECT_EQ("+0530", formatDatetime(parseTimestamp("1970-10-01"), "z"));
+  EXPECT_EQ(
+      "India Standard Time",
+      formatDatetime(parseTimestamp("1970-10-01"), "zzzz"));
 
-  setQueryTimeZone("Asia/Kolkata");
-  // We don't support more than 3 'z's yet.
-  EXPECT_THROW(
-      formatDatetime(parseTimestamp("1970-01-01"), "zzzz"), VeloxRuntimeError);
+  // Test a long long name.
+  setQueryTimeZone("Australia/Eucla");
+  EXPECT_EQ("+0845", formatDatetime(parseTimestamp("1970-10-01"), "z"));
+  EXPECT_EQ(
+      "Australian Central Western Standard Time",
+      formatDatetime(parseTimestamp("1970-10-01"), "zzzz"));
 
+  setQueryTimeZone("Asia/Kolkata");
   // Literal test cases.
   EXPECT_EQ("hello", formatDatetime(parseTimestamp("1970-01-01"), "'hello'"));
   EXPECT_EQ("'", formatDatetime(parseTimestamp("1970-01-01"), "''"));