hi mkobyakov
First, There were several typos in my question. Hadoop access account is ‘gpadmin’, not ‘sysadmin’.
and It’s the same in query. Using Different double quotes in query is typing error, too.
I am sorry to make you confused.
Now, I will answer your request.
- User that owns hdfs:// path is ‘gpadmin’.
- Different double quotes is typo.

Second query is corrected.
CREATE PIPELINE pi_hdfs
AS LOAD DATA HDFS 'hdfs://~~:8020/~~'
CONFIG '{"disable_gunzip": true}'
CREDENTIALS '{"user":"gpadmin"}'
INTO TABLE '~~'(data_line)
SET file_path = pipeline_source_file();
Additionally, I trying to run query with this syntax, too. but same error occurred.
CREDENTIALS '{"user":'gpadmin'}'
CREDENTIALS '{"user":gpadmin}'