Unit System v2 (#243)

* Separated `Time` unit into `TimeDelta` and `TimeStamp` + small fixes

Addition and subtruction between `Timestamp`s is not allowed, but any
other `Unit` operation/comparison is. `TimeDelta`s can be
added/subtructed to/form `Timestamp`s.

Deserialization of `Timestamp`:
- `Number` -> interpreted as millis from Epoch
- `Instant` (string representation) -> converted to Timestamp
- `Duration` (string representation) -> interpreted as duration since
  Epoch (warn msg is logged)

Deserialization of `TimeDelta` is the same as `Time` was before, with the
diference that when an `Instant` is converted to an timedelta since Epoch
a warning message is logged.

* Unit System v2

- Merged `BoundedPercentage` and `UnboundedPercentage`
- Overrided all operation defined in `Unit` in all subclasses to avoid
  as much as possible value classes being boxed in bytecode. If units are used as generics
  (hence also functions defined in Unit<T>) they are boxed (as double would if used as generic).
- All units companions now subclass `UnitId`, and can be used as keys
  (e.g `Map<UnitId, idk>`), while offering `max` `min` and `zero`
  methods.
- Division between the same unit now returns `Percentage`
- Added `Iterable<T>.averageOfUnitOrNull(selector (T) -> <specific unit>)`
- `ifNeg0ThenPos0()` now is optional and not invoked on every
  constructor
- Now methods in `Unit<T>` are all abstract, forcing override and avoid
  boxing in some cases
- Added `@UnintendedOperation` and `UnitOperationException` for methods
  that must be defined but are not intended for use (e.g. `Timestamp` +
  `Timestamp`)

1 files changed, 8 insertions, 1 deletions

diff --git a/opendc-trace/opendc-trace-parquet/src/main/kotlin/org/opendc/trace/util/parquet/exporter/Exporter.kt b/opendc-trace/opendc-trace-parquet/src/main/kotlin/org/opendc/trace/util/parquet/exporter/Exporter.kt
index 05f36530..4f46f573 100644
--- a/opendc-trace/opendc-trace-parquet/src/main/kotlin/org/opendc/trace/util/parquet/exporter/Exporter.kt
+++ b/opendc-trace/opendc-trace-parquet/src/main/kotlin/org/opendc/trace/util/parquet/exporter/Exporter.kt
@@ -32,6 +32,7 @@ import org.apache.parquet.schema.PrimitiveType.PrimitiveTypeName.DOUBLE
 import org.apache.parquet.schema.PrimitiveType.PrimitiveTypeName.FLOAT
 import org.apache.parquet.schema.PrimitiveType.PrimitiveTypeName.INT32
 import org.apache.parquet.schema.PrimitiveType.PrimitiveTypeName.INT64
+import org.apache.parquet.schema.Type
 import org.apache.parquet.schema.Types
 import org.opendc.trace.util.parquet.ParquetDataWriter
 import java.io.File
@@ -122,7 +123,13 @@ public class Exporter<T : Exportable>
                                 val valueToAdd: Any =
                                     column.getValue(
                                         record,
-                                    ) ?: return@forEachIndexed // Maybe add explicit check for optional fields
+                                    ) ?: let {
+                                        if (column.field.isRepetition(Type.Repetition.OPTIONAL)) {
+                                            return@forEachIndexed
+                                        } else {
+                                            throw RuntimeException("trying to insert null value in required column $column")
+                                        }
+                                    }
 
                                 startField(column.name, idx)
                                 when (column.primitiveTypeName) {