[Lazarus] Embedded database for Lazarus/Linux

[Santiago A.]

El 17/06/2010 9:39, Luca Olivetti escribió:
>
> "Concurrency
>
> SQLite allows multiple programs to be connected to the same database
> simultaneously. The embedded version of Firebird does not. If you run
> Firebird in client/server mode, it allows concurrent access with
> fine-grain locking. But in embedded mode, only one program can connect
> to the database at a time."
>
> Bye

If you write a program manages its own data,  configurations etc, you
can read sequential files, text files etc. But if the data is very
complex and there is a lot of data, instead of reinventing the wheel,
you can use a embedded  DB, like SQLlite or others. That is what
embedded RB were designed for, not to share data.

SQLite's concurrency is just fancy feature, not a very useful feature.
Concurrency in SQLite is pretty simple. Only a process can write
simultaneously, and it locks the whole file and has problems with
threads: Check http://www.sqlite.org/faq.html (5) (6). If you want a
program (a workstation) that manages data, and the rest of programs read
data, SQLite concurrency may be good for you. But even in this case, one
process is updating and several processes are reading, you can run into
problems: http://old.nabble.com/Memory-Usage-td23154686.html.

But if you plan to deploy several programs sharing the same data as
peers, updating and reading, SQLite is not the solution, you must use a
real RDBMS. You shouldn't rely on operating system file locking systems
and clients doing the right thing. You need a single process that
controls the file and schedules users' petitions, that is, a RDBMS.

But if you think that data will be seldom updated, SQLite may do job.
Just be aware that SQLite is not scalable for concurrency. Use the right
tool, for the right task.


Santiago A.