## 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

Column Type Description
`oid` `oid` Row identifier
`amprocfamily` `oid` (references `pg_opfamily`.`oid`) The operator family this entry is for
`amproclefttype` `oid` (references `pg_type`.`oid`) Left-hand input data type of associated operator
`amprocrighttype` `oid` (references `pg_type`.`oid`) Right-hand input data type of associated operator
`amprocnum` `int2` Support function number
`amproc` `regproc` (references `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`.