## 51.5. `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 51.5. `pg_amproc` Columns

Name | Type | References | Description
--- | --- | --- | ---
`oid` | `oid` |  | Row identifier (hidden attribute; must be explicitly selected)
`amprocfamily` | `oid` | ``pg_opfamily`.oid` | The operator family this entry is for
`amproclefttype` | `oid` | ``pg_type`.oid` | Left-hand input data type of associated operator
`amprocrighttype` | `oid` | ``pg_type`.oid` | Right-hand input data type of associated operator
`amprocnum` | `int2` |  | Support function number
`amproc` | `regproc` | ``pg_proc`.oid` | 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`.