From 765a21424af99ddbca50141aa4833f6b7da7bdcf Mon Sep 17 00:00:00 2001
From: Kevin Wilfong <kevinwilfong@meta.com>
Date: Tue, 22 Oct 2024 16:18:15 -0700
Subject: [PATCH] Add support for z, zz, zzz in format_datetime (#11323)

Summary:
Pull Request resolved: https://github.com/facebookincubator/velox/pull/11323

This diff adds support for JODA's z, zz, zzz patterns (all equivalent) in Presto's
forma_datetime function.

This is used to format time zone abbreviations.

Differential Revision: D64774281
---
 velox/functions/lib/DateTimeFormatter.cpp     | 34 +++++++++++++++----
 .../prestosql/tests/DateTimeFunctionsTest.cpp | 29 ++++++++++++----
 2 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/velox/functions/lib/DateTimeFormatter.cpp b/velox/functions/lib/DateTimeFormatter.cpp
index 5534ae62b6c6a..7d9c6e8ec5733 100644
--- a/velox/functions/lib/DateTimeFormatter.cpp
+++ b/velox/functions/lib/DateTimeFormatter.cpp
@@ -1167,10 +1167,17 @@ uint32_t DateTimeFormatter::maxResultSize(const tz::TimeZone* timezone) const {
         size += std::max((int)token.pattern.minRepresentDigits, 9);
         break;
       case DateTimeFormatSpecifier::TIMEZONE:
-        VELOX_NYI(
-            "Date format specifier is not yet implemented: {} ({})",
-            getSpecifierName(token.pattern.specifier),
-            token.pattern.minRepresentDigits);
+        if (token.pattern.minRepresentDigits <= 3) {
+          // The longest abbreviation according to here is 5, e.g. some time
+          // zones use the offset as the abbreviation, like +0530.
+          // 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);
+        }
 
         break;
       case DateTimeFormatSpecifier::TIMEZONE_OFFSET_ID:
@@ -1412,9 +1419,22 @@ int32_t DateTimeFormatter::format(
         } break;
 
         case DateTimeFormatSpecifier::TIMEZONE: {
-          // TODO: implement short name time zone, need a map from full name
-          // to short name
-          VELOX_UNSUPPORTED("time zone name is not yet supported");
+          VELOX_CHECK_NOT_NULL(
+              timezone,
+              "The time zone cannot be formatted if it is not present.");
+          if (token.pattern.minRepresentDigits <= 3) {
+            const std::string& abbrev =
+                tz::locateZone(timezone->id())
+                    ->tz()
+                    ->get_info(date::local_seconds(
+                        std::chrono::seconds(timestamp.getSeconds())))
+                    .first.abbrev;
+            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");
+          }
         } break;
 
         case DateTimeFormatSpecifier::TIMEZONE_OFFSET_ID: {
diff --git a/velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp b/velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp
index 97807df92a0e6..661874dda3fbd 100644
--- a/velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp
+++ b/velox/functions/prestosql/tests/DateTimeFunctionsTest.cpp
@@ -3269,6 +3269,24 @@ TEST_F(DateTimeFunctionsTest, formatDateTime) {
   EXPECT_EQ("+05:30", formatDatetime(parseTimestamp("1970-01-01"), "ZZ"));
   EXPECT_EQ("+0530", formatDatetime(parseTimestamp("1970-01-01"), "Z"));
 
+  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"));
+
+  // 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"));
+
+  // Test a long abbreviation.
+  setQueryTimeZone("Asia/Colombo");
+  EXPECT_EQ("+0530", formatDatetime(parseTimestamp("1970-10-01"), "z"));
+
+  setQueryTimeZone("Asia/Kolkata");
+  // We don't support more than 3 'z's yet.
+  EXPECT_THROW(
+      formatDatetime(parseTimestamp("1970-01-01"), "zzzz"), VeloxRuntimeError);
+
   // Literal test cases.
   EXPECT_EQ("hello", formatDatetime(parseTimestamp("1970-01-01"), "'hello'"));
   EXPECT_EQ("'", formatDatetime(parseTimestamp("1970-01-01"), "''"));
@@ -3313,15 +3331,14 @@ TEST_F(DateTimeFunctionsTest, formatDateTime) {
   EXPECT_THROW(
       formatDatetime(parseTimestamp("1970-01-01"), "'abcd"), VeloxUserError);
 
-  // System errors for patterns we haven't implemented yet.
+  // Time zone name patterns aren't supported when there isn't a time zone
+  // available.
   EXPECT_THROW(
-      formatDatetime(parseTimestamp("1970-01-01"), "z"), VeloxRuntimeError);
+      formatDatetime(parseTimestamp("1970-01-01"), "z"), VeloxUserError);
   EXPECT_THROW(
-      formatDatetime(parseTimestamp("1970-01-01"), "zz"), VeloxRuntimeError);
+      formatDatetime(parseTimestamp("1970-01-01"), "zz"), VeloxUserError);
   EXPECT_THROW(
-      formatDatetime(parseTimestamp("1970-01-01"), "zzz"), VeloxRuntimeError);
-  EXPECT_THROW(
-      formatDatetime(parseTimestamp("1970-01-01"), "zzzz"), VeloxRuntimeError);
+      formatDatetime(parseTimestamp("1970-01-01"), "zzz"), VeloxUserError);
 }
 
 TEST_F(DateTimeFunctionsTest, formatDateTimeTimezone) {