The benefits of using SQLite storage for the template cache are faster read and write operations when the number of cache elements is important.
I've never used it yet,but how can using SQLite by faster than plain file system?
IMO the overhead(initiating a connection) will make it slower.
BTW,can someone provide a demo how to use SQLite?
There is no real notion of "initiating a connection" : an SQLite database is stored as a single file, in the local filesystem ; so there is nothing like a network connection.
I suppose using an SQLite database can be seen as fast as there is only one file (the database), and not one file per template -- and each access to a file costs some resources ; the operating system might be able to cache accesses to one big file more efficiently to several accesses to several distinct small files.
About a "demo how to use SQLite", it kind of depends on the language you'll be using, but you can start by taking a look at the SQLite documentation, and the API that's available in your programming language ; accessing an SQLite DB is not that hard : basically, you have to :
It's not much different than with any other DB engine : the biggest difference is there is no need to setup any DB server.
The benefits of SQLite over a standard file system would lie in it's caching mechanism. SQLite stores data in pages and caches pages to memory. Repeated calls for data that are on pages already in memory will skip a call out to the file system.
There is some overhead in using SQLite though. When you connect to a SQLite database the engine reads and parses the schema. On our system, that takes 30ms (although it's usually less than 1ms for smaller schemas--we have just under a hundred tables and hundreds of triggers and indexes).