pg_amproc stores information about support
   procedures
   associated with index access method operator classes.  There is one
   row for each support procedure belonging to an operator class.
  
Table 3-5. pg_amproc Columns
| Name | Type | References | Description | 
|---|
| amopclaid | oid | pg_opclass.oid | the index opclass this entry is for | 
| amprocnum | int2 |  | support procedure index | 
| amproc | regproc | pg_proc.oid | OID of the proc |