>> Don't Load More Data Than You Have To <<
But hey! thats only half the story! Also: Don't hit the database
more *often* than you have to. So you ALSO need outerjoin fetching
where appropriate!
>> Tell Me What Has Changed. Don't Make Me Look! <<
These arguments go to performance. So where are the performance
numbers to back up these assertions. I have plenty of tests to
show that the overhead of dirtychecking is trivial compared
to the work involved in loading the objects in the first place!
This person has NEVER done any actual profiling. If they DID, they
would know the truth ;)
>> If thousands (or hundreds of thousands) of objects are loaded from the
database, committing these objects can be slower than necessary due to the
equality checks that have to be performed. <<
Ah, can't leave this one alone.
In Hibernate:
session.setFlushMode(FlushMode.NEVER)
will remove the need to do this in a transaction that just reads a
thousand objects. But nobody ever bothers to use this functionality
because it is, in fact, a TRIVIAL overhead compared to loading a
thousand objects off the database in the first place!
>> Also, the state of the object is
duplicated in memory, so this may cause memory scalability problems. <<
LOL!! This person is clueless. To verify this:
(1) Install JProbe
(2) Run Hibernate
(3) check how many objects your JDBC driver instantiates in the
process of retrieving an SQL ResultSet.
>> Jaxor never suffers from these scalability problems. Objects are
represented in
memory once. If they are updated, or deleted, then the session is notified
of the changed. No extra comparisons have to be done.<<
At MOST, the memory consumption of Hibernate could be 2 * Jaxor. But in
fact, including the memory consumed by the JDBC calls, the ratio is much
less than that.
Now, in my book, a CONSTANT factor memory overhead is never a
_scalability_ problem, by definition. Perhaps if you could show that
the overhead increased as the system scaled (which it doesn't), you
could make this argument. Scalability problems in large systems
usually revolve around *concurrency* issues, which Hibernate manages
beautifully.
Once again, I conclude that this author knows very little about the
subject (in this case, scalability).
>> Second part is about having a "Database synchronization tool to match
mapping information to the database schema" about handling simple "deltas"
to a schema and INFORMING about columns/tables that the metadata does NOT
cover...(maybe we should start maturing schemaupdate and build a
schemacomparison "tool" ?) <<
I am sceptical until I see something work in practice. I have never ever
worked on a site where, once a system was in production, the DBA would
let me use my litte auto-schema-updater on the live database. I think this
person lives in a theoretical world where developers manage production
databases ;)
>> Power of Text. <<
I think I said that first, in the Hibernate FAQ.
Was I a little harsh on this guy? Sorry ;)
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