Fix formatting of Etc/... time zones in Presto's datetime_format and …

…cast TSwTZ to varchar (facebookincubator#11409)

Summary:
Pull Request resolved: facebookincubator#11409

The file we use from Joda to generate time zone links (substitutions for certain time zone IDs that
we use when formatting) maps various versions of "UTC" to "Etc/GMT" and "Etc/UTC" as these are
the official IDs (see https://en.wikipedia.org/wiki/List_of_tz_database_time_zones ).

However, Joda also has logic at runtime to remove these prefixes and convert them to "UTC".  This
leads to Velox producing "Etc/GMT" or "Etc/UTC" when calling datetime_format with the "ZZZ" (or
more) pattern and when casting TSwTZ to varchar, while Joda produces "UTC".

To keep things simple, I've modified the script that generates our mapping of time zone IDs to simply
replace the Etc/GMT and Etc/UTC IDs with "UTC".  For cases like parsing, we already call
normalizeTimeZone on the time zone ID which does this (among other things), so this is consistent
with other places in the code, and, by doing it when generating the map, means we have to do less
normalization at runtime.

Reviewed By: xiaoxmeng

Differential Revision: D65348867

fbshipit-source-id: f39dc397b6c1be87a92aaa7dd93215df64c98b40

velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp

@@ -3572,6 +3572,38 @@ TEST_F(DateTimeFunctionsTest, formatDateTime) {
       "America/Los_Angeles",
       formatDatetime(parseTimestamp("1970-01-01"), "ZZZ"));
 
+  // Test the Etc/... time zones.
+  auto testFormatTimeZoneID =
+      [&](const std::string& inputTimeZoneID,
+          const std::string& expectedFormattedTimeZoneID) {
+        setQueryTimeZone(inputTimeZoneID);
+        EXPECT_EQ(
+            expectedFormattedTimeZoneID,
+            formatDatetime(parseTimestamp("1970-01-01"), "ZZZ"));
+      };
+  testFormatTimeZoneID("Etc/GMT", "UTC");
+  testFormatTimeZoneID("Etc/GMT+0", "UTC");
+  testFormatTimeZoneID("Etc/GMT+1", "-01:00");
+  testFormatTimeZoneID("Etc/GMT+10", "-10:00");
+  testFormatTimeZoneID("Etc/GMT+12", "-12:00");
+  testFormatTimeZoneID("Etc/GMT-0", "UTC");
+  testFormatTimeZoneID("Etc/GMT-2", "+02:00");
+  testFormatTimeZoneID("Etc/GMT-11", "+11:00");
+  testFormatTimeZoneID("Etc/GMT-14", "+14:00");
+  testFormatTimeZoneID("Etc/GMT0", "UTC");
+  testFormatTimeZoneID("Etc/Greenwich", "UTC");
+  testFormatTimeZoneID("Etc/UCT", "UTC");
+  testFormatTimeZoneID("Etc/Universal", "UTC");
+  testFormatTimeZoneID("Etc/UTC", "UTC");
+  testFormatTimeZoneID("Etc/Zulu", "UTC");
+  // These do not explicitly start with "Etc/" but they link to time zone IDs
+  // that do.
+  testFormatTimeZoneID("GMT0", "UTC");
+  testFormatTimeZoneID("Greenwich", "UTC");
+  testFormatTimeZoneID("UCT", "UTC");
+  testFormatTimeZoneID("UTC", "UTC");
+  testFormatTimeZoneID("Zulu", "UTC");
+
   setQueryTimeZone("Asia/Kolkata");
   // Literal test cases.
   EXPECT_EQ("hello", formatDatetime(parseTimestamp("1970-01-01"), "'hello'"));

velox/type/tz/TimeZoneLinks.cpp

@@ -67,19 +67,19 @@ const std::unordered_map<std::string, std::string>& getTimeZoneLinks() {
         {"Cuba", "America/Havana"},
         {"Egypt", "Africa/Cairo"},
         {"Eire", "Europe/Dublin"},
-        {"Etc/GMT+0", "Etc/GMT"},
-        {"Etc/GMT-0", "Etc/GMT"},
-        {"Etc/GMT0", "Etc/GMT"},
-        {"Etc/Greenwich", "Etc/GMT"},
-        {"Etc/UCT", "Etc/UTC"},
-        {"Etc/Universal", "Etc/UTC"},
-        {"Etc/Zulu", "Etc/UTC"},
+        {"Etc/GMT+0", "UTC"},
+        {"Etc/GMT-0", "UTC"},
+        {"Etc/GMT0", "UTC"},
+        {"Etc/Greenwich", "UTC"},
+        {"Etc/UCT", "UTC"},
+        {"Etc/Universal", "UTC"},
+        {"Etc/Zulu", "UTC"},
         {"GB", "Europe/London"},
         {"GB-Eire", "Europe/London"},
-        {"GMT+0", "Etc/GMT"},
-        {"GMT-0", "Etc/GMT"},
-        {"GMT0", "Etc/GMT"},
-        {"Greenwich", "Etc/GMT"},
+        {"GMT+0", "UTC"},
+        {"GMT-0", "UTC"},
+        {"GMT0", "UTC"},
+        {"Greenwich", "UTC"},
         {"Hongkong", "Asia/Hong_Kong"},
         {"Iceland", "Atlantic/Reykjavik"},
         {"Iran", "Asia/Tehran"},
@@ -101,7 +101,7 @@ const std::unordered_map<std::string, std::string>& getTimeZoneLinks() {
         {"ROK", "Asia/Seoul"},
         {"Singapore", "Asia/Singapore"},
         {"Turkey", "Europe/Istanbul"},
-        {"UCT", "Etc/UTC"},
+        {"UCT", "UTC"},
         {"US/Alaska", "America/Anchorage"},
         {"US/Aleutian", "America/Adak"},
         {"US/Arizona", "America/Phoenix"},
@@ -114,10 +114,10 @@ const std::unordered_map<std::string, std::string>& getTimeZoneLinks() {
         {"US/Mountain", "America/Denver"},
         {"US/Pacific", "America/Los_Angeles"},
         {"US/Samoa", "Pacific/Pago_Pago"},
-        {"UTC", "Etc/UTC"},
-        {"Universal", "Etc/UTC"},
+        {"UTC", "UTC"},
+        {"Universal", "UTC"},
         {"W-SU", "Europe/Moscow"},
-        {"Zulu", "Etc/UTC"},
+        {"Zulu", "UTC"},
         {"America/Buenos_Aires", "America/Argentina/Buenos_Aires"},
         {"America/Catamarca", "America/Argentina/Catamarca"},
         {"America/Cordoba", "America/Argentina/Cordoba"},

velox/type/tz/gen_timezone_links.py

@@ -115,8 +115,15 @@ def main():
             if columns[0] != "Link":
                 continue
 
+            # Officially the GMT/UTC time zone IDs start with Etc/ so Joda
+            # includes this in its link files. Joda ends up removing this
+            # prefix at runtime though, so we just skip ahead and do it here.
+            tz_value = columns[1]
+            if tz_value == "Etc/GMT" or tz_value == "Etc/UTC":
+                tz_value = "UTC"
+
             entries.append(
-                entry_template.substitute(tz_key=columns[2], tz_value=columns[1])
+                entry_template.substitute(tz_key=columns[2], tz_value=tz_value)
             )
 
     print(cpp_template.substitute(entries="\n".join(entries)))