Pump
Pumps define stream-to-stream dataflow. A pump fetches rows from upstream streams (often called upstreams), process them, and pushes them to a downstream.
Let's look at an example pump:
Pump definition
CREATE PUMP pump1 AS
INSERT INTO downstream1 (col1, col2)
SELECT STREAM
...,
...
FROM upstream1
...;
Note that this statements includes SELECT
sub-statement to fetch and process rows from upstreams, and INSERT
sub-statement to push result rows to downstreams.
This statement defines the following pump (the edge in the diagram).
Some pumps, such as with join operations, have 2 or more upstreams, while the number of donwstream must be always 1.
Pumps with WINDOW
clause create window and others do not.