The mi_eval_am_qual() accessor function
The mi_eval_am_qual() function evaluates parts of a qualification that the access method does not set to MI_VALUE_TRUE or MI_VALUE_FALSE.
Syntax
mi_boolean
mi_eval_am_qual(MI_ROW *row, MI_AM_QUAL_DESC *qualDesc);- row
- Points to the row structure.
- qualDesc
- Points to the qualification descriptor.
Usage
The am_getnext purpose
function can call mi_eval_am_qual() to obtain results
for any qualifications that the access method cannot complete. Before
the access method can call mi_eval_am_qual(), it
must call mi_row_create() to assemble a row.
Tip: Both mi_row_create() and mi_eval_am_qual() can
increase response time and CPU usage. Call them only if necessary.
If mi_eval_am_qual() returns MI_TRUE, am_getnext returns MI_ROWS. If mi_eval_am_qual() returns MI_FALSE, am_getnext disregards the current row, does not return a value, and starts to evaluate the next row.
Return values
- MI_TRUE
- Indicates that the row qualifies.
- MI_FALSE
- Indicates that the row does not qualify.