Spark: We should probably say why we cannot process the snapshot in SparkMicroBatchStream

[rajarshisarkar]

We should probably say why we cannot process the snapshot here:

iceberg/spark/v3.2/spark/src/main/java/org/apache/iceberg/spark/source/SparkMicroBatchStream.java

Lines 201 to 209 in cbf56a3

	private boolean shouldProcess(Snapshot snapshot) {
	String op = snapshot.operation();
	Preconditions.checkState(!op.equals(DataOperations.DELETE) || skipDelete,
	"Cannot process delete snapshot: %s", snapshot.snapshotId());
	Preconditions.checkState(
	op.equals(DataOperations.DELETE) || op.equals(DataOperations.APPEND) || op.equals(DataOperations.REPLACE),
	"Cannot process %s snapshot: %s", op.toLowerCase(Locale.ROOT), snapshot.snapshotId());
	return op.equals(DataOperations.APPEND);
	}

[jackye1995]

@rajarshisarkar would you like to add the documentation?

[rajarshisarkar]

Yes, documentation would be better. @RussellSpitzer Any thoughts?

[RussellSpitzer]

I think we should change the exception and add documentation. Exception should probably be "Cannot process snapshot, Structured Streaming does not support snapshots of type X"