我的目标是不断地将传入的parquet文件放入delta lake，进行查询，并将结果放入restapi。所有文件都在s3存储桶中。

//listen for changes
val df = spark.readStream().parquet("s3a://myBucket/folder")

//write changes to delta lake
df.writeStream()
    .format("delta")
    .option("checkpointLocation", "s3a://myBucket-processed/checkpoint")
    .start("s3a://myBucket-processed/")
    .awaitTermination() //this call lives in another thread (because it's blocking)

//this is a bad example
val query = df.select(convertedColumnNames) 
query.show()

//another bad example:
spark.readStream().format("delta").load("s3a://myBucket-processed/").select(convertedColumnNames).show()

//org.apache.spark.sql.AnalysisException: Queries with streaming sources must be executed with writeStream.start();;

我如何从三角洲湖得到过滤后的数据？