Qualification Descriptor

A qualification descriptor, or MI_AM_QUAL_DESC structure, describes the conditions in the WHERE clause of an SQL statement. For a detailed description of qualification processing, including examples, refer to Processing Queries.

Use the VTI mi_scan_quals() function to obtain a pointer to the qualification descriptor from the scan descriptor.

The following accessor functions extract information from a qualification descriptor.

Accessor Function

Return Value

mi_qual_boolop()

The operator type (AND or OR) of a qualification that is a complex expression

mi_qual_column()

The position that the column argument to a qualification function occupies within a row

mi_qual_commuteargs()

MI_TRUE if the argument list begins with a constant rather than a column value

mi_qual_const_depends_hostvar()

MI_TRUE if a constant argument to a qualification function acquires a value at runtime from a host variable

mi_qual_const_depends_outer()

MI_TRUE if the value of a particular constant argument can change each rescan

mi_qual_constant()

The runtime value of the constant argument to a qualification function

mi_qual_constant_nohostvar()

The value specified in the WHERE clause for the constant argument to a qualification function

mi_qual_constisnull()

MI_ TRUE if the value of a constant argument to a qualification function is NULL

mi_qual_constisnull_nohostvar()

MI_ TRUE if the WHERE clause specifies a NULL value as the constant argument to a qualification function

mi_qual_funcid()

The routine identifier of a qualification function

mi_qual_funcname()

The name of a qualification function

mi_qual_handlenull()

MI_TRUE if the qualification function accepts null arguments

mi_qual_issimple()

MI_TRUE if the qualification contains one function rather than a complex expression

mi_qual_needoutput()

MI_TRUE if the qualification function supplies an output parameter value

Obtain and set a pointer to the output-parameter value with mi_qual_setoutput().

mi_qual_negate()

MI_TRUE if the qualification includes the operator NOT

mi_qual_nquals()

The number of nested qualifications in a complex expression, or 0 for a simple qualification that contains no Boolean operators

mi_qual_qual()

Pointer to one qualification in a complex qualification descriptor or to the only qualification

mi_qual_value()

One of the following possible values:

• MI_VALUE_NOT_EVALUATED until the qualification returns a result
• MI_VALUE_TRUE if the qualification returns MI_TRUE
• MI_VALUE_FALSE if the qualification returns MI_FALSE

Set the results in the qualification descriptor with mi_qual_setvalue(). Reset the qualification descriptor to MI_VALUE_NOT_EVALUATED with mi_init_am_qual().

The following accessor functions set values in the descriptor.

Accessor Function

Value Set

mi_qual_setvalue()

The result from executing the qualification operator or function

mi_qual_setoutput()

A host-variable value

mi_qual_setreopt()

An indicator to force reoptimization between rescans

mi_eval_am_qual()

MI_TRUE if the current row satisfies the current qualification

mi_init_am_qual()

MI_VALUE_NOT_EVALUATED to reset all results fields in a qualification descriptor