Te serviría esto ??
SELECT a.attname, pg_catalog.format_type(a.atttypid, a.atttypmod)
FROM pg_catalog.pg_attribute a, pg_class c
WHERE a.attrelid = c.oid
AND c.relname = 'NOMBRE_DE_TU_TABLA'
AND a.attnum > 0
AND a.attname = 'NOMBRE_DE_TU_COLUMNA'
AND NOT a.attisdropped
ORDER BY a.attnum
Y esto?
SELECT column_name, data_type, character_maximum_length
FROM information_schema.columns
WHERE table_name = 'NOMBRE_DE_TU_TABLA'
AND column_name = 'NOMBRE_DE_TU_COLUMNA';