AMQ Filter

AMQF stands for 'Approximate Member Query Filter'. The filter can be turned on to reduce a number of possible disk accesses during point-looks using sp_get() or sp_delete(). The filter is not used for range queries by sp_cursor(), cursor implementation has its own caching scheme.

Following variable can be set to enable or disable AMQF usage: db.database_name.amqf

sp_setint(env, "db.test.amqf", 1);

By default the filter is turned off, because normally there is no need for it. But there are some cases, when it can be useful.

The filter should be used to reduce LRU washout in Persistent Caching.

Sophia uses the Quotient Filter for the AMQF purpose.