PG_AGGREGATE

PG_AGGREGATE records information about aggregate functions. Each entry in PG_AGGREGATE is an extension of an entry in PG_PROC. The PG_PROC entry carries the aggregate's name, input and output data types, and other information that is similar to ordinary functions.

Table 1 PG_AGGREGATE columns

Name	Type	Reference	Description
aggfnoid	regproc	PG_PROC.proname	PG_PROC proname of the aggregate function
aggtransfn	regproc	PG_PROC.proname	Transition function
aggcollectfn	regproc	PG_PROC.proname	Collect function
aggfinalfn	regproc	PG_PROC.proname	Final function (0 if none)
aggsortop	oid	PG_OPERATOR.oid	Associated sort operator (0 if none)
aggtranstype	oid	PG_TYPE.oid	Data type of the aggregate function's internal transition (state) data
agginitval	text	-	Initial value of the transition state. This is a text column containing the initial value in its external string representation. If this column is null, the transition state value starts from null.
agginitcollect	text	-	Initial value of the collection state. This is a text column containing the initial value in its external string representation. If this column is null, the collection state value starts from null.
aggkind	"char"	-	Type of the aggregate function: n: normal aggregate o: ordered set aggregate
aggnumdirectargs	smallint	-	Number of direct parameters (non-aggregation-related parameters) of the aggregate function of the ordered set aggregate type. For an aggregate function of the normal aggregate type, the value is 0.