I see that Intent lock is defined in the source code, see db_lockmode_t*, however I don't find that intent locks are used in the Transaction Datastore for Btree Access Method. It looks like that BDB just use Read-write lock and based on pagel-level locking for Btree access method.
I believe use of DB_LOCK_WWRITE and DB_LOCK_READ_UNCOMMITTED is the implementation details for making read-uncommitted-transaction to read write-transaction modification. it doesn't improve lock granularity.
what i understand is right?