| Return the cost of exact key lookup.
Return the estimated cost of calling ScanController.fetch()
on the current conglomerate, with start and stop positions set such
that an exact match is expected.
This call returns the cost of a fetchNext() performed on a scan which
has been positioned with a start position which specifies exact match
on all keys in the row.
Example:
In the case of a btree this call can be used to determine the cost of
doing an exact probe into btree, giving all key columns. This cost
can be used if the client knows it will be doing an exact key probe
but does not have the key's at optimize time to use to make a call to
getScanCost()
Parameters:
validColumns - A description of which columns to return fromrow on the page into "templateRow." templateRow,and validColumns work together todescribe the row to be returned by the fetch - see RowUtil for description of how these three parameters work together to describe a fetched "row".
Parameters:
access_type - Describe the type of access the query will beperforming to the ScanController. STORECOST_CLUSTERED - The location of one scanis likely clustered "close" to the previous scan. For instance if the query plan wereto used repeated "reopenScan()'s" to probefor the next key in an index, then this flagshould be be specified. If this flag is not set then each scan will be costed independantof any other predicted scan access. The cost of the fetch.
exception:
StandardException - Standard exception policy.
See Also: RowUtil | 