RTREE_COST_ADJUST_VALUE environment variable

The RTREE_COST_ADJUST_VALUE environment variable specifies a coefficient that support functions of user-defined data types can use to estimate the cost of an R-tree index for queries on UDT columns.

is a floating-point number, where 1value1000, specifying a multiplier for estimating the cost of using an index on a UDT column.

For spatial queries, the I/O overhead tends to exceed by far the CPU cost, so by multiplying the uncorrected estimated cost by an appropriate value from this setting, the database server can make better cost-based decisions on how to implement queries on UDT columns for which an R-tree index exists.