??? <2004wqg2008 at 163.com> wrote: > HI,all > SQLite retrieves the compressed records is slower than the uncompressed > records about 30%. > How can improve the problem? and anyone any suggustion? > > best regards > wqg
What is your SQLite page size? If you access small records, you're better off with a small page size (fewer bytes to read and decompress). If you have large BLOBs you can afford large page sizes (better compression, which can result in less I/Os). Which compression algorithm are you using? You can see the compression algorithm the first few bytes of the database file. Some compression algorithms are faster than others. For example, lz4hc decompression is much faster than zlib (about 10x faster I think) at the cost of compressing less than zlib. Are you reading only or also writing to the DB? Some algorithms have very different speed for compression and decompression. And of course, make sure that your queries minimize the number of SQLite pages read, which is always good whether you compress, but especially true with compressed DB. Watch for queries doing full table scan, etc. Regards Dominique
