On 24 Jan 2013, at 2:41pm, Patrick <patr...@spellingbeewinnars.org> wrote:
> I bought the Apress book. There is a chapter on internals. I have tried to > read what I could find on the net too but I am still mixed up about something. > > I don't know how sqlite interacts with visitors while maintaining state. If > everything was read into memory it would be easy to imagine how things could > work but then how would a second application access it? > > I am guessing other DBs that have authentication are socket based but I > guessing sqlite is not socket based. > > If it was all based on disk writes then multiple applications could read and > write to it, via a queue with locked files. Is this the case? What sort of > inter-process communication is sqlite based on? You stated off by making some assumptions which would normally be correct, but are not valid for SQLite. Your last two paragraphs suggest you realized what was really happening. There is no persistent SQLite Server process, accepting requests from many users. SQLite has no multi-user model and is not primarily intended for use as a server/client database. All changes are performed by changing data in the database file or in temporary 'journal' files on disk. The only thing you could say is shared between users is whether the file on disk is locked (indicating that it's currently being updated by a user) or not. Think of SQLite as the simple database system your TV uses to list channel names, or your mobile phone uses to keep its phone book (both of which are, in fact, things SQLite really is used for with literally millions of installations). The fact that SQLite works at all with huge datasets being accessed by many users at once is just a result of good programming. As your questions indicate, if you're starting off a programming project intending to use big datasets accessed concurrently by many users across a network, SQLite is probably not the right database engine to use. More about this can be found at <http://www.sqlite.org/whentouse.html> Simon. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
