db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Mike Matrigali <mikem_...@sbcglobal.net>
Subject transaction semantics on property conglomerate?
Date Thu, 15 Dec 2005 01:17:06 GMT
Just reading the code.  The property conglomerate provides
a transactional way to store "database" properties.  For
performance it caches the values in a java hash table, so
that subsequent look ups don't have to go to disk.  It
doesn't expect many properties so it's current implementation
has no disk based indexing.

It looks to me like a hash table miss is always going have
to do a table scan, so looking up a property that is usually
not defined is going to be a fairly expensive operation.  It
is going to get locks, it is going to mark your transaction
active, and currently is going to hold locks on the conglomerate
until the transaction commits.

Given that no locks are obtained on the hash table would it
be appropriate to read the values at read committed
rather than serializable?

View raw message