Про поддержку Unicode ничего не скажу - не пользуюсь,
а насчет BLOB -"спец интерфейс для large object'ов " лежит здесь : ./исходники постгреса/contrib/lo
Peter Mount <peter@retep.org.uk>; June 13 1998
PostgreSQL type extension for managing Large Objects
----------------------------------------------------

Overview

One of the problems with the JDBC driver (and this affects the ODBC driver
also), is that the specification assumes that references to BLOBS (Binary
Large OBjectS) are stored within a table, and if that entry is changed, the
associated BLOB is deleted from the database.