Should this query be cached in the query cache or filter cache.
void setCache(boolean cache)
Returns the cost of this query, used to order checking of filters that are not cached.
If getCache()==false && getCost()>=100 && this instanceof PostFilter, then
the PostFilter interface will be used for filtering.
void setCost(int cost)
If true, the clauses of this boolean query should be cached separately. This is not yet implemented.