I am running Spark 2.2 and trying out structured streaming. I have the following code:

from pyspark.sql import functions as F

df=frame \

    .withWatermark("timestamp","1 minute") \

    .groupby(F.window("timestamp","1 day"),*groupby_cols) \


query = frame.writeStream \


.option("checkpointLocation", '\some\chkpoint')





It prints out a bunch of aggregated rows to console. When I run the same query with outputMode("append") however, the output only has the column names, no rows. I was originally trying to output to parquet, which only supports append mode. I was seeing no data in my parquet files, so I switched to console output to debug, then noticed this issue. Am I misunderstanding something about how append mode works?