On Jul 21, 2008, at 2:10 AM, [EMAIL PROTECTED] wrote: > > Hello, > > to answer the following question: > > Amount of memory for caching one page with x byte page size? > > I found in the Draft 3.6.0 Doc the following information: > > > PRAGMA page_size = bytes; > > Query or set the page size of the database. > The page size may only be set if the database has not yet been > created. > The page size must be a power of two greater than or equal to 512 and > less than or equal to SQLITE_MAX_PAGE_SIZE. > The maximum value for SQLITE_MAX_PAGE_SIZE is 32768. > > > > PRAGMA default_cache_size = Number-of-pages; > > Query or change the maximum number of database disk pages that SQLite > will hold in memory at once. > Each page uses 1K on disk and about 1.5K in memory. ....... > > > Obviously you have an overhand per page-size to calculate the memory > requirement for caching on page. > > Do I understand this right?
Right. When a page is loaded into the cache, SQLite allocates memory for the page data (1024 bytes, or whatever size you are using) and also memory for a structure full of other variables required by each cached page (page number, dirty flag, is-journalled flag, various pointers for linked lists, lots of stuff). The overhead probably isn't quite 512 bytes, but as a rule of thumb this formula works Ok. Dan. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
