merge: Introduce schema for trace API (#88)

This pull request updates the OpenDC trace API to support proper specification 
of a schema of the tables exposed by the traces. This functionality makes it easier 
for the API consumer to understand the types exposed by the API.

## Implementation Notes :hammer_and_pick:

* Introduce type system for trace API
* Add benchmarks for odcvm trace format 
* Add benchmarks for Azure trace format
* Add conformance suite for OpenDC trace API 

## External Dependencies :four_leaf_clover:

* N/A

## Breaking API Changes :warning:

* Removal of typed `TableColumn`. Instead, `TableColumn` instances are now 
   used to describe the columns belonging to some table.
* `TableReader` and `TableWriter` do not support accessing arbitrary objects 
   anymore. Instead, only the types supported by the type system are exposed.

2 files changed, 3 insertions, 8 deletions

diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt
index 1a9b9ee1..5206d02b 100644
--- a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt
@@ -29,9 +29,5 @@ import org.opendc.trace.TableColumn
  * A class used by the [TraceFormat] interface for describing the metadata of a [Table].
  *
  * @param columns The available columns in the table.
- * @param partitionKeys The table columns that act as partition keys for the table.
  */
-public data class TableDetails(
-    val columns: List<TableColumn<*>>,
-    val partitionKeys: List<TableColumn<*>> = emptyList()
-)
+public data class TableDetails(val columns: List<TableColumn>)
diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt
index 47761e0f..eff6fa83 100644
--- a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt
@@ -22,7 +22,6 @@
 
 package org.opendc.trace.spi
 
-import org.opendc.trace.TableColumn
 import org.opendc.trace.TableReader
 import org.opendc.trace.TableWriter
 import java.nio.file.Path
@@ -69,11 +68,11 @@ public interface TraceFormat {
      *
      * @param path The path to the trace to open.
      * @param table The name of the table to open a [TableReader] for.
-     * @param projection The list of [TableColumn]s to project or `null` if no projection is performed.
+     * @param projection The name of the columns to project or `null` if no projection is performed.
      * @throws IllegalArgumentException If [table] does not exist.
      * @return A [TableReader] instance for the table.
      */
-    public fun newReader(path: Path, table: String, projection: List<TableColumn<*>>?): TableReader
+    public fun newReader(path: Path, table: String, projection: List<String>?): TableReader
 
     /**
      * Open a [TableWriter] for the specified [table].