postgresql – How to remove unused temporary files from Google Cloud SQL managed by Postgres?

We migrated to Google Cloud SQL, created multiple databases, and imported a lot of data. Beside, there was quite a large amount of queries that were interrupted here and there, which left garbage in the form of temporary files. And the use of storage has far exceeded 1 TB.

postgres => SELECT data_name, time_files AS "Temporary files", pg_size_pretty (temp_bytes) AS "Size of temporary files" FROM pg_stat_database;
datname | Temporary files | Size of temporary files
--------------- + ----------------- + ---------------- ---------
cloudsqladmin | 0 | 0 bytes
template0 | 0 | 0 bytes
postgres | 0 | 0 bytes
template1 | 0 | 0 bytes
first | 33621 | 722 GB
second | 9 | 3399 MB
third | 293313 | 153 GB
(7 rows)

According to the results of the query above, we have about 1 TB of potentially useless files. There are two questions:

1) How to identify temporary files not used by queries being executed?
2) How to delete them because this postgres is managed by Google Cloud SQL?