Support routines
The opaque data type support routines you can specify
in the New Opaque Type wizard fall into the following categories:
| Category | Description |
|---|---|
| Internal support routines for data types | These routines are automatically called by the
database server when it processes the data types; they cannot be called
from SQL. This category includes Text Input and Output Functions, Binary Send and Receive Functions, text file import and export functions, binary file import and export functions, and the Assign() function and Destroy() procedure. |
| Data type comparison functions | The Equal() and NotEqual() operator functions call the Compare() internal support function to compare two opaque data types when called from SQL: for example, to support an ORDER BY clause. |
| B-tree access method support and strategy functions | Access method support functions are called by
the server when it processes secondary indexes. Access method strategy
functions are called by the user in SQL; they signal the database
server to use the associated access method to retrieve the result
of the query. The B-tree support function is Compare(). The B-tree strategy functions are Equal(), LessThan(), GreaterThan(), LessThanOrEqual(), and GreaterThanOrEqual(); they are all bound to operators. |
| Overloaded built-in functions | Overloaded mathematical functions take one or
two opaque data types, perform the mathematical operation, and return
the resulting opaque data type. The mathematical functions are Plus(), Minus(), Times(), Divide(), Positive(),
and Negate(). The overloaded Concat() function concatenates two opaque data types. The overloaded Hash() function supports hashing for an opaque data type. |
| Statistics support functions | Statistics support functions are called by the server when it updates statistics for an opaque data type. You update statistics with the SQL statement UPDATE STATISTICS. Statistics support functions compile information about the values in an opaque data type column that the optimizer can use when it creates a query plan. The statistics support functions are OpaqueStatCollect(), OpaqueStatPrint(), Opaque_SetMinValue(), Opaque_SetMaxValue(), and Opaque_SetHistogram(). |
For more information, see the HCL Informix® DataBlade Developers Kit User's Guide.