Caches and performance tuning

mvSQLite keeps a client-side page cache that is always consistent with persisted data. Cache invalidation is differential: on transaction boundaries, only remotely changed pages are invalidated.

When the size of the page cache is set to a large enough value, it essentially converges into an in-memory consistent snapshot of the database. At this point, the minimum network overhead of a read-only transaction is just a get-read-version request at the beginning.

Performance tuning

Apps have different data access patterns: some apps usually do point gets and sets, while others like to do full-table scans. Also, under some deployments the latency between mvstore and clients can be high (although this is not recommended). The default runtime parameters are optimized for point-gets/small range scans and low-latency networks.

If:

• your application likes to scan large ranges
• you are running something like VACUUM or PRAGMA integrity_check
• the latency between mvstore and the client is greater than 5ms

follow the advice below:

• Set MVSQLITE_PAGE_CACHE_SIZE to a larger value (the unit is number of pages & the default page size is 8192 bytes).
• Set MVSQLITE_PREFETCH_DEPTH to a larger value. Recommended: 100.