I want to delete all external tables present in a schema in a particular sanbox in redshift - amazon-web-services

Question

I want to delete all external tables present in a schema in a particular sanbox in redshift
ERROR Exception: DROP EXTERNAL TABLE cannot be executed from a function or procedure
CREATE OR REPLACE PROCEDURE "workspace"."qw"()
AS
$$
DECLARE
t_sql VARCHAR(32000);
t_script_name VARCHAR(100) := 'load_sample_dcdr$table_cleanup';
t_table_name VARCHAR(100);
t_start_runtime TIMESTAMP;
t_row_count BIGINT;
t_current_db_YYYYMM VARCHAR;
t_current_db VARCHAR(100);
cur_loop REFCURSOR;
BEGIN
-- IF UPPER(t_current_db) = UPPER(current_database()) THEN
t_sql := 'select distinct(table_name) from svv_all_columns where schema_name=''deleted'' and database_name=''singh_sandbox''';
OPEN cur_loop FOR EXECUTE t_sql;
LOOP
FETCH cur_loop INTO t_table_name;
EXIT WHEN NOT FOUND;
EXECUTE 'DROP table IF EXISTS deleted.'||t_table_name||' cascade';
t_row_count=t_row_count+1;
END LOOP;
CLOSE cur_loop;
-- END IF;
END;
$$ LANGUAGE plpgsql;

Answer 1

This is because DROP EXTERNAL TABLE cannot be run inside a transaction block (BEGIN - END). This makes running this command inside a stored procedure impossible since the procedure is its own transaction block. [There are reasons for this but that isn't important for the question.]
So to do this you will need some code running outside of Redshift that can issue the DROP statements outside of a transaction block. Some benches can perform actions like this but most don't. You could write a Lambda function, or even a bash script can do this if you have the aws and psql clis installed. Or you can issue the statements manually but that could be a pain if the list of tables is large.