"Rajan, Vivek K" <[EMAIL PROTECTED]> wrote: > > * What is the max number of databases which can be attached to a > single process using SQLite?
That is set at compile-time by the MAX_ATTACH macro. The default value is 10. There are places in the code that use an integer as a bit vector to keep track of some aspects of attached database, so you cannot increase MAX_ATTACH above 32 on 32-bit machines. > * Has someone tried attached large number of databases with > SQLite, and are there any performance tradeoffs in working with multiple > database attached thru SQLite? > SQLite uses about the same amount of memory and CPU working with multiple attached databases as it would working with the databases if they were opened individually. If you have 10 attached databases and you make a change to just one of them, that is pretty much the same as if the other 9 were not even attached. If you make a change to 2 databases, then the commit has to do twice as may fsync() calls (which is by far the single slowest operation that SQLite ever does) and there is a bit of additional overhead to sync and manage the "master journal" used to make sure that the commit is atomic across both databases. So it is a little bit more expensive than committing to two separate databases. But not a lot. And the commit is atomic across both databases which is something you would not get otherwise. Query performance with multiple attached databases should be no different from a single database. -- D. Richard Hipp <[EMAIL PROTECTED]>
