Qualification descriptor
A qualification descriptor, or MI_AM_QUAL_DESC structure, describes the conditions in the WHERE clause of an SQL statement.
Use the VII 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 an index entry |
| 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 strategy 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 strategy function |
| mi_qual_funcname() | The name of a strategy 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_stratnum() | The ordinal number of the operator-class strategy function |
The following accessor functions set values in the descriptor.
| Accessor function | Value set |
|---|---|
| mi_qual_setoutput() | A host-variable value |
| mi_qual_setreopt() | An indicator to force reoptimization between rescans |