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

The possible values and their meanings are defined by the types in pg_type.h. The main two types are polymorphic (isPolymorphicType) and non-polymorphic.

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.

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