Qualification descriptor
A qualification descriptor, or MI_AM_QUAL_DESC structure, describes the conditions in the WHERE clause of an SQL statement.
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 run time 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_constant_typeid() | The data type of 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_nparams() | The number of parameters in the qualification descriptor |
| 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:
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 running 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 |