To view the progress of a running CREATE MATERIALIZED VIEW, CREATE INDEX, or CREATE SINK statement, run the following command: 
SELECT * FROM rw_catalog.rw_ddl_progress;

 ddl_id |         ddl_statement         | progress
--------+-------------------------------+----------
   1026 | CREATE INDEX idx ON sbtest1(c) | 69.02%
(1 row)
Note that the progress given here is just an estimate. To abort a running CREATE MATERIALIZED VIEW, CREATE INDEX, or CREATE SINK statement, press CTRL+C (or Control+C). For example: 
CREATE MATERIALIZED VIEW mv2 AS SELECT * FROM mv1;
------------------------
^CCancel request sent
ERROR:  QueryError: Scheduler error: Cancelled: create
Alternatively, you can use the SHOW JOBS command to get all streaming jobs (that is, the creation of a materialized view, an index, a table, a source, or a sink) that are in progress. The IDs, specific statements, and their progresses will be returned in the result. You can then cancel specific jobs by their IDs using the CANCEL JOBS command. The CANCEL JOBS command will return IDs of the jobs that are canceled successfully.
Show all jobs

SHOW JOBS;
------RESULT
  Id  |                     Statement                     | Progress
------+---------------------------------------------------+----------
 1010 | CREATE MATERIALIZED VIEW mv3 AS SELECT *FROM mv1  | 2.21%
 1012 | CREATE MATERIALIZED VIEW mv2 AS SELECT* FROM mv1  | 0.86%
Cancel jobs
CANCEL JOBS 1010, 1012;
------RESULT
Id
------
 1012
 1010

SHOW JOBS

CANCEL JOBS