dataflow pipeline design for real time aggregation analysis

i have a case as below:

1) use pubsub as input in dataflow and load the stream data to bigquery 2) select aggregated result from bigquery and load to pubsub as output 3) client that listen to pubsub for display

e.g. i have sales transaction and want to see regional (aggregated) sales figure real-time. i knew that i can use 2 pipelines for load data to bigquery (1) and other dataflow pipeline to get aggregated result and push to pubsub.

Is there any way to do in a single pipeline? as i don't want to build a orchestration layer (i.e. after 1st pipeline finished, call 2 pipeline). and initialing pipeline is costly.

thanks.