PG_AMOP

PG_AMOP records information about operators associated with access method operator families. There is one row for each operator that is a member of an operator family. A family member can be either a search operator or an ordering operator. An operator can appear in more than one family, but cannot appear in more than one search position nor more than one ordering position within a family.

Table 1 PG_AMOP columns

Name	Type	Reference	Description
oid	oid	-	Row identifier (hidden attribute, which must be specified)
amopfamily	oid	PG_OPFAMILY.oid	Operator family of this entry
amoplefttype	oid	PG_TYPE.oid	Left-hand input data type of the operator
amoprighttype	oid	PG_TYPE.oid	Right-hand input data type of the operator
amopstrategy	smallint	-	Number of operator strategies
amoppurpose	"char"	-	Operator purpose, either s for search or o for ordering
amopopr	oid	PG_OPERATOR.oid	OID of the operator
amopmethod	oid	PG_AM.oid	Operator family of the index access method
amopsortfamily	oid	PG_OPFAMILY.oid	The B-tree operator family according to which this entry sorts for an ordering operator (0 for a search operator)

A search operator entry indicates that an index of this operator family can be searched to find all rows satisfying WHERE indexed_column operator constant. Obviously, such an operator must return a Boolean value, and its left-hand input type must match the index's column data type.

An ordering operator entry indicates that an index of this operator family can be scanned to return rows in the order represented by ORDER BY indexed_column operator constant. Such an operator could return any sortable data type, though again its left-hand input type must match the index's column data type. The exact semantics of ORDER BY are specified by the amopsortfamily column, which must reference the B-tree operator family for the operator's result type.