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Le 14/12/11 22:05, Mark Stanton a écrit :

Hi Mark,

If I'm not mistaken (although I might be and I haven't got the time 
to go back and check) and odb file is effectively a zip file with 
various things in it.


I believe HSQL is a "cut down" database, on the basis that a lot of 
the bells and whistles of a full database engine aren't required by 
small applications.  Hence it's a small, fast database, without it's 
own data storage, I imagine, since the data for it *is* kept in the 
odb file.

Hmm, I wouldn't say "cut down", it is actually rather good, certainly in
its latest incarnation, which is not included as the engine for OOo/LO
ODB files.

It can be used with its own independent storage too, but then you have
to set it up in server/client mode, i.e. LO becomes the client (via and
ODB file) and hsqldb.jar runs as a "server". In the current setup of
LO/hsqldb, the data is effectively stored within the ODB file. In fact,
the whole of the hsqldb.jar is loaded into memory when the ODB file is
opened. This is then used (via a Java2uno bridge, at least that is how I
understand it) to access tables, queries, forms, etc, so everything
resides in memory, which is fine...until your app crashes, you run out
of memory, or you have a power cut, and cry your heart out,
throw a wobbly, or swear til the air turns blue, when you discover your
precious ODB file has either been corrupted or the data you have been
entering for the last 3 hours has not been saved. And all of this is
absolutely not hsqldb's fault, but OOo/LO's because of the way it was
decided at the time to integrate hsqldb into OOo.

There are moves afoot to switch to SQLite as the default db backend
engine. Whether that will actually work, whether it will result in one
or several files, remains to be seen. Personally, I hope that the
multifile option will be chosen, and that we will just use the LO ODB
container as a front end, so that the db data will always be accessible
outside of the LO app and readable by any SQLite compliant reader.

Here's hoping...


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