MI_AM_QUAL_DESC* mi_scan_quals(MI_AM_SCAN_DESC *scanDesc);
The am_getnext purpose function calls mi_scan_quals() to obtain the starting point from which it evaluates a row and then passes the return value (a pointer) from this function to all the qualification-descriptor accessor functions.
A valid pointer indicates the start of the qualification descriptor for this scan. A NULL-valued pointer indicates that the access method should return all rows.
See the description of the accessor functions in Qualification Descriptor.