grep oid zabbix-1.6/create/schema/postgresql.sql
snmp_oid varchar(255) DEFAULT '' NOT NULL,

while housekeeper.c has

#elif defined(HAVE_POSTGRESQL)
deleted = DBexecute("delete from %s where oid in (select oid from %s where %s=" ZBX_FS_UI64 " limit 500)",
housekeeper.tablename,
housekeeper.tablename,
housekeeper.field,
housekeeper.value);

So in my logs I get lot's of errors about not haveing oid like
Oct 2 19:20:07 clu004 postgres[15302]: [7-1] ERROR: column "oid" does not exist at character 42
Oct 2 19:20:07 clu004 postgres[15302]: [7-2] STATEMENT: delete from history where oid in (select oid from history where itemid=121680 limit 500)