Обсуждение: specific questions regarding Oid and finding out the granularity of the lock

http://developer.postgresql.org/docs/postgres/explicit-locking.html

where is the documentation on different types of lock modes for row level locks? Does anyone know?

What is the difference between relId (of type Oid) and dbId (of type Oid) in LOCKTAG (in Lock.h) struct?

Is it true that from a PROCLOCK object, we find out whether it's a table level/ row level lock from the holding[] array (i.e., from the modes?) If not, how do we know whether it's a table level/ row level lock?

Does the relId and dbId tells us the exact row (and, or) table associated with the LOCK?

These are real specific questions, thank you so much for anyone who answers... :)

Sumaira