Re: Queries with streaming sources must be executed with writeStream.start()

[Felix Cheung]

What is newDS?
If it is a Streaming Dataset/DataFrame (since you have writeStream there) then 
there seems to be an issue preventing toJSON to work.

________________________________
From: kant kodali <kanth...@gmail.com>
Sent: Saturday, September 9, 2017 4:04:33 PM
To: user @spark
Subject: Queries with streaming sources must be executed with 
writeStream.start()

Hi All,

I  have the following code and I am not sure what's wrong with it? I cannot 
call dataset.toJSON() (which returns a DataSet) ? I am using spark 2.2.0 so I 
am wondering if there is any work around?


 Dataset<String> ds = newDS.toJSON().map(()->{some function that returns a 
string});
 StreamingQuery query = ds.writeStream().start();
 query.awaitTermination();