Fix current_time handling for legacy timestamp semantics

Correct current_time behavior in legacy timestamp semantics when the session time zone’s current offset differs from its offset on 1970-01-01.

Author: imjalpreet

presto-main-base/src/main/java/com/facebook/presto/operator/scalar/DateTimeFunctions.java

@@ -117,13 +117,12 @@ public static long currentTime(SqlFunctionProperties properties)
         // and we need to have UTC millis for packDateTimeWithZone
         long millis = UTC_CHRONOLOGY.millisOfDay().get(properties.getSessionStartTime());
 
-        if (!properties.isLegacyTimestamp()) {
-            // However, those UTC millis are pointing to the correct UTC timestamp
-            // Our TIME WITH TIME ZONE representation does use UTC 1970-01-01 representation
-            // So we have to hack here in order to get valid representation
-            // of TIME WITH TIME ZONE
-            millis -= valueToSessionTimeZoneOffsetDiff(properties.getSessionStartTime(), getDateTimeZone(properties.getTimeZoneKey()));
-        }
+        // However, those UTC millis are pointing to the correct UTC timestamp
+        // Our TIME WITH TIME ZONE representation does use UTC 1970-01-01 representation
+        // So we have to hack here in order to get valid representation
+        // of TIME WITH TIME ZONE
+        millis -= valueToSessionTimeZoneOffsetDiff(properties.getSessionStartTime(), getDateTimeZone(properties.getTimeZoneKey()));
+
         try {
             return packDateTimeWithZone(millis, properties.getTimeZoneKey());
         }

presto-main-base/src/test/java/com/facebook/presto/operator/scalar/TestDateTimeFunctions.java

@@ -20,7 +20,6 @@
 import org.joda.time.DateTime;
 import org.testng.annotations.Test;
 
-import static com.facebook.presto.common.type.TimeWithTimeZoneType.TIME_WITH_TIME_ZONE;
 import static com.facebook.presto.common.type.TimestampWithTimeZoneType.TIMESTAMP_WITH_TIME_ZONE;
 import static com.facebook.presto.common.type.VarcharType.createVarcharType;
 
@@ -57,20 +56,6 @@ public void testLocalTime()
         }
     }
 
-    @Test
-    public void testCurrentTime()
-    {
-        Session localSession = Session.builder(session)
-                // we use Asia/Kathmandu here to test the difference in semantic change of current_time
-                // between legacy and non-legacy timestamp
-                .setTimeZoneKey(KATHMANDU_ZONE_KEY)
-                .setStartTime(new DateTime(2017, 3, 1, 15, 45, 0, 0, KATHMANDU_ZONE).getMillis())
-                .build();
-        try (FunctionAssertions localAssertion = new FunctionAssertions(localSession)) {
-            localAssertion.assertFunctionString("CURRENT_TIME", TIME_WITH_TIME_ZONE, "15:45:00.000 Asia/Kathmandu");
-        }
-    }
-
     @Test
     public void testLocalTimestamp()
     {

presto-main-base/src/test/java/com/facebook/presto/operator/scalar/TestDateTimeFunctionsBase.java

@@ -186,6 +186,19 @@ private static long epochDaysInZone(TimeZoneKey timeZoneKey, long instant)
         return LocalDate.from(Instant.ofEpochMilli(instant).atZone(ZoneId.of(timeZoneKey.getId()))).toEpochDay();
     }
 
+    @Test
+    public void testCurrentTime()
+    {
+        Session localSession = Session.builder(session)
+                // we use Asia/Kathmandu here, as it has different zone offset on 2017-03-01 and on 1970-01-01
+                .setTimeZoneKey(KATHMANDU_ZONE_KEY)
+                .setStartTime(new DateTime(2017, 3, 1, 15, 45, 0, 0, KATHMANDU_ZONE).getMillis())
+                .build();
+        try (FunctionAssertions localAssertion = new FunctionAssertions(localSession)) {
+            localAssertion.assertFunctionString("CURRENT_TIME", TIME_WITH_TIME_ZONE, "15:45:00.000 Asia/Kathmandu");
+        }
+    }
+
     @Test
     public void testFromUnixTime()
     {

presto-main-base/src/test/java/com/facebook/presto/operator/scalar/TestDateTimeFunctionsLegacy.java

@@ -20,7 +20,6 @@
 import org.joda.time.DateTime;
 import org.testng.annotations.Test;
 
-import static com.facebook.presto.common.type.TimeWithTimeZoneType.TIME_WITH_TIME_ZONE;
 import static com.facebook.presto.common.type.TimestampWithTimeZoneType.TIMESTAMP_WITH_TIME_ZONE;
 import static com.facebook.presto.common.type.VarcharType.VARCHAR;
 import static com.facebook.presto.common.type.VarcharType.createVarcharType;
@@ -56,20 +55,6 @@ public void testLocalTime()
         }
     }
 
-    @Test
-    public void testCurrentTime()
-    {
-        Session localSession = Session.builder(session)
-                // we use Asia/Kathmandu here to test the difference in semantic change of current_time
-                // between legacy and non-legacy timestamp
-                .setTimeZoneKey(KATHMANDU_ZONE_KEY)
-                .setStartTime(new DateTime(2017, 3, 1, 15, 45, 0, 0, KATHMANDU_ZONE).getMillis())
-                .build();
-        try (FunctionAssertions localAssertion = new FunctionAssertions(localSession)) {
-            localAssertion.assertFunctionString("CURRENT_TIME", TIME_WITH_TIME_ZONE, "15:30:00.000 Asia/Kathmandu");
-        }
-    }
-
     @Test
     public void testLocalTimestamp()
     {