Luca Olivetti wrote:
Hello,
I'm writing an embedded application that will need a small database
(no more than a couple thousand records), and I though sqlite could
do it.
It probably won't have any graphical interface, so I don't need all
the goodies of a TDataset descendant, OTOH I like some other things a
dataset will buy me.
Needless to say, the application must be rock solid, running
unattended 24/7.
I made a quick test with the sqlite3ds component that's included in
lazarus and with SQLitePass http://source.online.free.fr/
I dropped either dataset in a form with a datasource and a dbgrid (as
suggested in the wiki).
My first impression (and as every first impression may just be wrong)
is tha sqlite3ds doesn't work well with a dbgrid, because it doesn't
automatically update the underlying database and so it doesn't catches
exceptions when you, e.g, try to insert a duplicate. What's worse,
when I call ApplyUpdates it silently discards the data (I would have
expected at least an exception, but I see that there's no exception
raised and neither an event is called in case of errors in
TCustomSqliteDataset.ApplyUpdates).
The behavior is by design (follows KISS philosophy).
- Update on post: sqliteds keeps the records in memory, works with them
(add,update,delete) and than send the changes to the database when the
user decides (more or less like sqldb). To update the database each time
a change occurs add ApplyUpdates in the OnPost event.
- ApplyUpdates error handling: Error is handled just does not follows
the exception model. Check if ApplyUpdates is false. If so check
ReturnCode (see sqlite docs for values) and ReturnString values.
- Primary key handling: sqliteds automatically handles primary key in
two ways. First add a AutoInc field to the table (Using
FieldDefs.Add/CreateTable) and sqliteds will ensure it will always be
unique and not null without user intervention. Second, if you have a
integer field as primary key set AutoIncrementKey to true and PrimaryKey
to the field name.
If the primary key is not integer the user must handle it yourself.
SQLitePass seems more solid (again, only with this simple test), since
it automatically updates the database and raises an exception
immediately if I try to insert a duplicate key. OTOH it raises a
RunError(204) when I close the form.
Pros of sqlite3ds:
- included in lazarus
- author active on this mailing list
- ...?
Cons of sqlite3ds:
- incomplete (?) implementation
Sure.
- doesn't really check errors
See above.
- ...?
- Undocumented features (to be fixed soon)
PS: I would recommend version from fpc 214 which has a lot of bug fixes.
Luiz
_________________________________________________________________
To unsubscribe: mail [EMAIL PROTECTED] with
"unsubscribe" as the Subject
archives at http://www.lazarus.freepascal.org/mailarchives
