Base table columns where TOASTing is possible

SELECT n.nspname AS table_schema,
c.relname AS table_name,
at.attname AS column_name,
tp.typname AS column_data_type_name,
tbt.typname AS column_base_data_type_name,
CASE WHEN at.attstorage ='p' THEN 'plain'
WHEN at.attstorage='e' THEN 'external'
WHEN at.attstorage='m' THEN 'main'
WHEN at.attstorage='x' THEN 'extended'
END AS column_toasting_strategy
FROM pg_attribute at INNER JOIN pg_class c ON at.attrelid=c.oid
INNER JOIN pg_namespace AS n ON n.oid=c.relnamespace
INNER JOIN pg_authid AS a ON n.nspowner=a.oid
INNER JOIN pg_type AS tp ON at.atttypid=tp.oid
LEFT JOIN pg_type AS tbt ON tp.typbasetype=tbt.oid 
WHERE (nspname='public' OR rolname<>'postgres')
AND c.relkind IN ('r')
AND at.attisdropped='f'
AND at.attnum>0
AND tp.typlen = -1
ORDER BY table_schema, table_name;