Write or choose strategy and support functions

In a query, the WHERE clause might specify a strategy function to qualify or filter rows. The following clauses represent the same strategy function, which compares the index key cost to a constant: 
WHERE equal(cost, 100)
WHERE cost = 100
Support functions build and scan the index and can perform any of the following tasks for a secondary access method:
  • Build an index
  • Search for specific key values
  • Add and delete index entries
  • Reorganize the index to accommodate new entries
The access method can call the same support function to perform multiple tasks. For example, an access method might call a between() support function to retrieve keys for the WHERE clause to test and locate the entries immediately greater than and less than a new index entry for an INSERT command.
Tip: If possible, use the built-in B-tree operators or the operator class that a registered DataBlade® module provides. Write new functions only if necessary to fit the data types that the secondary access method indexes.