Hi 1) Question about SQLITE_CONFIG_SCRATCH
In SQLite documentation about SQLITE_CONFIG_SCRATCH, I read: === BEGIN QUOTE https://sqlite.org/c3ref/c_config_getmalloc.html === SQLite will never require a scratch buffer that is more than 6 times the database page size. If SQLite needs needs additional scratch memory beyond what is provided by this configuration option, then sqlite3_malloc() will be used to obtain the memory needed. === END QUOTE === I stumbled upon code where the scratch buffer size is configured to only 10 KB only, yet some DB have 16KB page sizes: const int KSize = 10*1024; const int KBufferCount = 8; static uint64_t sqliteScratchBuffer[KSize*KBuferSize/sizeof(uint64_t)]; status = sqlite3_config( SQLITE_CONFIG_SCRATCH, &sqliteScratchBuffer[0], KSize, KBufferCount); Is it safe to have only 10KB of scratch buffer when DB page size can be 16KB? Is it ideal? I don't find guidelines about configuring SQLITE_CONFIG_SCRATCH. What happens if the scratch buffer was bigger than 6*page size? Would memory just be wasted? (since doc says it never allocate more than 6*page size). 2) Question about SQLITE_CONFIG_PAGECACHE In order to reduce the number of malloc calls, I consider configuring SQLITE_CONFIG_PAGECACHE with a static buffer. However, the application opens multiple databases with various page sizes (1KB, 4MB, 8MB, 16MB). So what happens if if do for example: // Max DB page size is 16KB. SQLite doc says to add 40 bytes for page header. const int KPageSize = 16*1024 + 40; const int KPageCount= 512; static uint64_t sqlitePageCache[KPageSize*KPageCount/sizeof(uint64_t)]; status = sqlite3_config( SQLITE_CONFIG_PAGECACHE, &sqlitePageCache[0], KPageSize, KPageCount); Will SQLite use 16KB (=KPageSize) in that buffer to store each page of DBs even for the DBs where page size is only 1KB or 4KB or 8KB? If so, it will waste memory for 1KB, 4KB or 8KB pages and SQLITE_CONFIG_PAGECACHE does not look like a good idea in such case. Regards Dominique _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
