gerashegalov commented on code in PR #18272:
URL: https://github.com/apache/iceberg/pull/18272#discussion_r4112538694
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parquet/src/main/java/org/apache/iceberg/parquet/ParquetUtil.java:
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@@ -173,15 +174,34 @@ public static boolean isIntType(PrimitiveType
primitiveType) {
}
/**
- * Method to read timestamp (parquet Int96) from bytebuffer. Read 12 bytes
in byteBuffer: 8 bytes
- * (time of day nanos) + 4 bytes(julianDay)
+ * Reads 12 INT96 bytes in the buffer's byte order as microseconds since the
Unix epoch.
+ *
+ * <p>Submicrosecond precision is truncated.
+ *
+ * @throws ArithmeticException if the timestamp overflows a long
*/
public static long extractTimestampInt96(ByteBuffer buffer) {
- // 8 bytes (time of day nanos)
long timeOfDayNanos = buffer.getLong();
- // 4 bytes(julianDay)
int julianDay = buffer.getInt();
- return TimeUnit.DAYS.toMicros(julianDay - UNIX_EPOCH_JULIAN)
- + TimeUnit.NANOSECONDS.toMicros(timeOfDayNanos);
+ return timestampInt96(julianDay, timeOfDayNanos / 1000, MICROS_PER_DAY);
+ }
+
+ /**
+ * Reads 12 INT96 bytes in the buffer's byte order as nanoseconds since the
Unix epoch.
+ *
+ * @throws ArithmeticException if the timestamp overflows a long
+ */
+ public static long extractTimestampInt96Nanos(ByteBuffer buffer) {
+ long timeOfDayNanos = buffer.getLong();
+ int julianDay = buffer.getInt();
+ return timestampInt96(julianDay, timeOfDayNanos, NANOS_PER_DAY);
+ }
+
+ private static long timestampInt96(int julianDay, long timeOfDay, long
ticksPerDay) {
+ long days = julianDay - UNIX_EPOCH_JULIAN;
+ // Shift negative days towards the epoch to keep the lower long boundary
representable.
+ return days < 0
+ ? Math.addExact(Math.multiplyExact(days + 1, ticksPerDay), timeOfDay -
ticksPerDay)
Review Comment:
Should we protect against subtraction wrapping for corrupt timeOfDay
ticksPerDay produce a legit value?
```suggestion
? Math.addExact(Math.multiplyExact(days + 1, ticksPerDay),
Math.subtractExact(timeOfDay, ticksPerDay))
```
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