init research

dataframe/plugins/kotlin-dataframe/testData/box/join_1.kt

@@ -0,0 +1,27 @@
+import org.jetbrains.kotlinx.dataframe.*
+import org.jetbrains.kotlinx.dataframe.annotations.*
+import org.jetbrains.kotlinx.dataframe.api.*
+import org.jetbrains.kotlinx.dataframe.io.*
+
+@DataSchema
+data class Sessions(
+    val roomId: Int
+)
+
+@DataSchema
+data class Rooms(
+    val id: Int,
+    val sort: Int,
+    val name: String,
+)
+
+fun box(): String {
+    val rooms = dataFrameOf(Rooms(1, 2, "n"))
+    val sessions = dataFrameOf(Sessions(1))
+
+    val df = sessions.join(rooms.group { id and name and sort }.into("room")) { roomId.match(right.room.id) }
+    df.roomId
+    df.room.sort
+    df.room.name
+    return "OK"
+}