That's music to my ears.
Thanks for sharing, Jan.
Within a year or two I will migrate from derby to H2 because at some
point I know I will need a database that I can modify to my heart's
delight :-)
- rami
Hi,
sorry for late reply, I was on holiday.
I wrote a few patches for H2 (NIO, soft reference cache, customized
indexing). I don't know theoretical SQL stuff, but Thomas's code is
really easy to follow and understand. It took me 4 hours in train to
understand most of code !!! Finding right location is just mather of
10 minutes debugging.
I consider H2 as best Java code I ever saw. Considering complexity of
problems it solves, number of features and incredible compactness of
code.
I really wish all programs would be written in the same way.
Jan
On Fri, Apr 9, 2010 at 11:48 AM, Rami Ojares<[email protected]> wrote:
Also a big thanks from me for sharing your experiences in such a clear
headed fashion.
There are people on this list who are interested to hear other people's
experiences about h2 codebase.
And to hear comparisons with other databases was most interesting!
- rami
On 9.4.2010 10:15, James Gregurich wrote:
The key feature that attracted my attention was MVCC. Based on what I have
read, that technique is what all the big boys are using to maximize their
performance. I figured that approach would likely work well for my needs.
I also spent time studying the source code for Firebird& Postgresql to
see if I could adapt either of them to work as an embedded db. Neither
project was coded very well. Firebird's code seemed fairly chaotic....though
better than SQLite. PostgresSQL is fairly well-written, but has an
insufficient level of abstraction. It's code is too married to the original
way it was intended to run..namely a collection of processes that
communicate via IPC. It would be a major effort to yank out all the IPC and
replace it with normal mutexes and memory management. Firebird would be
easier to adapt, but it was still not trivial because their code isn't well
written. It is hard to trace through Firebird's code and figure out how it
works. Firebird needs to be coded from scratch using modern C++ techniques.
Finally, I'm doing commercial software with lots of proprietary IP....so
anything GPL is poison....can't use it.
H2's code is fairly well written and structured. Its easy to follow,
understand and trace through. The license doesn't require me to make our
core intellectual property public. So, It is the best choice IMO.
I'd say the authors of H2 should have been more disciplined when coding,
but overall, they did a good job. There tends to be a fair amount of
redundant storing of references to objects. For instance, if a subclass
needs a reference to an object and its parent already has a reference to
that object, instead of reusing the parent's reference, the subclass stores
a second reference to it. Also, there needs to be religious use of prefixes
to distinguish data members, local variables and static variables from one
another. naming variables like "newConnection" with no indication of scope
makes code harder to read and understand. Also, I prefer better
encapsulation of data members. I instruct my guys that only constructors,
destructors and accessor functions may directly reference data members...all
other member functions must go through accessors....its a little extra work
up front to write accessors, but it generally pays for itself when you need
to evolve the code later on.
BTW: I did discover what I think is a race condition in SET EXCLUSIVE if
multithreaded mode is on. It looked to me like you could end up with two
sessions thinking they had exclusive access. However, that was in an older
version of your code. You may have fixed that by now. I don't know yet. I
just refreshed my copy of your repository today after many months.
On Apr 8, 2010, at 11:47 PM, Sylvain Pointeau wrote:
Seems interesting, could you point on the issues in sqlite3 and compare
them with H2 and how H2 solved them?
Best regards,
Sylvain
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