pg_amproc
   The catalog pg_amproc stores information about
   support functions associated with access method operator families.  There
   is one row for each support function belonging to an operator family.
  
Table 52.5. pg_amproc Columns
| Name | Type | References | Description | 
|---|---|---|---|
| oid | oid | Row identifier (hidden attribute; must be explicitly selected) | |
| amprocfamily | oid |  | The operator family this entry is for | 
| amproclefttype | oid |  | Left-hand input data type of associated operator | 
| amprocrighttype | oid |  | Right-hand input data type of associated operator | 
| amprocnum | int2 | Support function number | |
| amproc | regproc |  | OID of the function | 
   The usual interpretation of the
   amproclefttype and amprocrighttype fields
   is that they identify the left and right input types of the operator(s)
   that a particular support function supports.  For some access methods
   these match the input data type(s) of the support function itself, for
   others not.  There is a notion of “default” support functions for
   an index, which are those with amproclefttype and
   amprocrighttype both equal to the index operator class's
   opcintype.