The hard part is to do it portably. I use a multicast socket that writes the change-event. Then I use a select() call on the multicast socket in other clients- if they see the change event, they incorporate the new data into their cache.
If you want it reasonably seamless, create triggers that evaluate a dummy-function that calls your notify: (e.g. SELECT foo() FROM table LIMIT 1) On Sun, 2004-05-09 at 18:39, Chris Waters wrote: > Hi, > > I need the ability to tell if changes have been made in the database. Kind > of like the LISTEN capability in Postgresql. In particular I need to know > if: > > * A row was inserted. > * A row was deleted. > * A row was modified. > > I would like to implement this through a callback that an application could > register. The callback would specify the operation that was performed, the > affected table and maybe the rowid affected. > > If the rowid is reported then for operations that affect a large number of > rows there would be a performance penalty to call the callback per row. For > my application this is not a problem, but perhaps when the callback is > specified the application could indicate whether it wants per row, or per > table notification. > > I am looking for ideas on where I should hook into the source code to add > this functionality. From what I have seen so far it looks like I could > change the implementation of the Delete and MakeRecord VM instructions to do > the callback. > > I haven't thought through the timing implications yet. Ideally when a row is > inserted, code in the callback could query the newly inserted row. I am not > 100% sure at what point the row becomes visible for query. > > I would welcome any insight since this is my first attempt (of many I have > lots of features I want :-) to modify the sqlite code. > > Thanks, > > Chris. > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
