PG_AMPROC

PG_AMPROC records information about the support procedures associated with the access method operator families. There is one row for each support procedure that belongs to an operator family.

Table 1 PG_AMPROC columns

Name	Type	Reference	Description
oid	oid	-	Row identifier (hidden attribute, which must be specified)
amprocfamily	oid	PG_OPFAMILY.oid	Operator family of this entry
amproclefttype	oid	PG_TYPE.oid	Left-hand input data type of the associated operator. For details about the possible values and their description, see pg_type.h.
amprocrighttype	oid	PG_TYPE.oid	Right-hand input data type of the associated operator. For details about the possible values and their description, see pg_type.h.
amprocnum	smallint	-	Support procedure number
amproc	regproc	PG_PROC.proname	OID of the procedure

The usual interpretation of the amproclefttype and amprocrighttype columns is that they identify the left and right input types of the operator(s) that a particular support procedure supports. For some access methods, these match the input data type(s) of the support procedure itself; for others not. There is a notion of "default" support procedures for an index, which are those with amproclefttype and amprocrighttype both equal to the index opclass's opcintype.