[SPARK-17914][SQL] Fix parsing of timestamp strings with nanoseconds

Author: aokolnychyi

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

@@ -32,7 +32,7 @@ import org.apache.spark.unsafe.types.UTF8String
  * Helper functions for converting between internal and external date and time representations.
  * Dates are exposed externally as java.sql.Date and are represented internally as the number of
  * dates since the Unix epoch (1970-01-01). Timestamps are exposed externally as java.sql.Timestamp
- * and are stored internally as longs, which are capable of storing timestamps with 100 nanosecond
+ * and are stored internally as longs, which are capable of storing timestamps with microsecond
  * precision.
  */
 object DateTimeUtils {
@@ -399,6 +399,11 @@ object DateTimeUtils {
       digitsMilli += 1
     }
 
+    while (digitsMilli > 6) {
+      segments(6) /= 10
+      digitsMilli -= 1
+    }
+
     if (!justTime && isInvalidDate(segments(0), segments(1), segments(2))) {
       return None
     }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/DateTimeUtilsSuite.scala

@@ -34,6 +34,22 @@ class DateTimeUtilsSuite extends SparkFunSuite {
     ((timestamp + tz.getOffset(timestamp)) / MILLIS_PER_DAY).toInt
   }
 
+  test("nanoseconds truncation") {
+    def checkStringToTimestamp(originalTime: String, expectedParsedTime: String) {
+      val parsedTimestampOp = DateTimeUtils.stringToTimestamp(UTF8String.fromString(originalTime))
+      assert(parsedTimestampOp.isDefined, "timestamp with nanoseconds was not parsed correctly")
+      assert(DateTimeUtils.timestampToString(parsedTimestampOp.get) === expectedParsedTime)
+    }
+
+    checkStringToTimestamp("2015-01-02 00:00:00.123456789", "2015-01-02 00:00:00.123456")
+    checkStringToTimestamp("2015-01-02 00:00:00.100000009", "2015-01-02 00:00:00.1")
+    checkStringToTimestamp("2015-01-02 00:00:00.000050000", "2015-01-02 00:00:00.00005")
+    checkStringToTimestamp("2015-01-02 00:00:00.12005", "2015-01-02 00:00:00.12005")
+    checkStringToTimestamp("2015-01-02 00:00:00.100", "2015-01-02 00:00:00.1")
+    checkStringToTimestamp("2015-01-02 00:00:00.000456789", "2015-01-02 00:00:00.000456")
+    checkStringToTimestamp("1950-01-02 00:00:00.000456789", "1950-01-02 00:00:00.000456")
+  }
+
   test("timestamp and us") {
     val now = new Timestamp(System.currentTimeMillis())
     now.setNanos(1000)