Off by default. Some complex queries (e.g. those involving
categories, or proximities closer than "page") can take more time to
determine exact result hit counts. In some cases it may cause
timeouts. Enabling this option will determine hit counts much faster,
and using less CPU, though at the expense of accuracy. The hit
counts for complex queries will generally be overestimated (it will
say there are more results than there really are).