Remove the timezone conversions

Author: Fokko

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala

@@ -471,7 +471,7 @@ abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression wit
     case StringType =>
       buildCast[UTF8String](_, s => DateTimeUtils.stringToDate(s, zoneId).orNull)
     case DoubleType =>
-      buildCast[Double](_, daysSinceEpoch => convertTz(daysSinceEpoch.toInt))
+      buildCast[Double](_, daysSinceEpoch => daysSinceEpoch.toInt)
     case TimestampType =>
       // throw valid precision more than seconds, according to Hive.
       // Timestamp.nanos is in 0 to 999,999,999, no more than a second.
@@ -1110,8 +1110,7 @@ abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression wit
             $evNull = true;
           }
          """
-      case DoubleType => (c, evPrim, evNull) =>
-        code"$evPrim = org.apache.spark.sql.catalyst.util.DateTimeUtils.convertTz((int)$c);"
+      case DoubleType => (c, evPrim, evNull) => code"$evPrim = (int) $c;"
       case TimestampType =>
         val zid = getZoneId()
         (c, evPrim, evNull) =>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala

@@ -422,10 +422,6 @@ object DateTimeUtils {
     Instant.ofEpochSecond(secs, mos * NANOS_PER_MICROS)
   }
 
-  def daysToInstant(daysSinceEpoch: SQLDate): Instant = {
-    Instant.ofEpochSecond(daysSinceEpoch * SECONDS_PER_DAY)
-  }
-
   def instantToDays(instant: Instant): Int = {
     val seconds = instant.getEpochSecond
     val days = Math.floorDiv(seconds, SECONDS_PER_DAY)
@@ -825,21 +821,6 @@ object DateTimeUtils {
     instantToMicros(rebasedDateTime.toInstant)
   }
 
-  /**
-   * Convert the date `ts` from one date to another.
-   *
-   * TODO: Because of DST, the conversion between UTC and human time is not exactly one-to-one
-   * mapping, the conversion here may return wrong result, we should make the timestamp
-   * timezone-aware.
-   */
-  def convertTz(ts: SQLDate, fromZone: ZoneId, toZone: ZoneId): SQLDate = {
-    val rebasedDateTime = daysToInstant(ts).atZone(toZone).toLocalDateTime.atZone(fromZone)
-    instantToDays(rebasedDateTime.toInstant)
-  }
-
-  // Convenience method for making it easier to only pass the first argument in Java codegen
-  def convertTz(ts: SQLDate): SQLDate = convertTz(ts, ZoneOffset.UTC, defaultTimeZone().toZoneId)
-
   /**
    * Returns a timestamp of given timezone from utc timestamp, with the same string
    * representation in their timezone.