On 20 Mar 2013, at 10:17am, Neo Anderson <[email protected]> wrote:
> Sorry, what do you mean on question 2? > > Can I use the buffered fopen family functions or not? I believe Dan is concerned about some issues with ACID and crash-recovery which will be introduced if you add an extra level of buffering. To ensure data integrity is is vital that the bits on the disk are a perfect reflection of the data in the database. This ensures that two processes trying to access the same data agree on what the data is, and also that if a process crashes while it's writing data to the database, the files on the disk (which are what's going to be found when the database is next opened) correctly reflect the history of committed transactions and are as up-to-date as possible. By buffering file operations you are introducing a set of delays to your operations. Consequently some of the 'state' of your data is neither committed nor uncommitted, but stuck somewhere in buffers. A DBMS which takes great pains to be as much ACID <http://en.wikipedia.org/wiki/ACID> as possible is one place where you would want to avoid buffering. So yes, technically, SQLite won't throw a fit if you use buffered calls. But using them will break ACID in cases of simultaneous access and recovery from crashes, power loss, broken cables, etc.. So it shouldn't be used in anything except conditions where the programmers knows everything about where their program will be used -- perhaps a one-off program which will only ever be run on the programmers own personal hardware. If you have written unbuffered code and it is /too/ slow to be useful, by all means get back to us and we can suggest things to tackle. But if rather than /too/ slow, it is just a bit slower than you think it could be, then buffering is not one of the best things to look at. Simon. _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
