Truncate parent table but not children
Use the ONLY key word:

TRUNCATE ONLY public.history_uint;

The manual:


  If ONLY is specified before the table name, only that table is
  truncated. If ONLY is not specified, the table and all its descendant
  tables (if any) are truncated. Optionally, * can be specified after
  the table name to explicitly indicate that descendant tables are included.


The schemas where parent and children live are only relevant as far as user privileges on the schema are concerned. Otherwise it's all the same to Postgres.