pg_aggregate

pg_aggregate

The pg_aggregate table stores information about aggregate functions. An aggregate function is a function that operates on a set of values (typically one column from each row that matches a query condition) and returns a single value computed from all these values. Typical aggregate functions are sum, count, and max. 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_catalog.pg_aggregate
column type references description
aggfnoid regproc pg_proc.oid Aggregate function OID
aggtransfn regproc pg_proc.oid Transition function OID
aggcombinefn regproc   Combine function OID (zero if none)
aggfinalfn regproc pg_proc.oid Final function OID (zero if none)
agginitval text   The initial value of the transition state. This is a text field containing the initial value in its external string representation. If this field is NULL, the transition state value starts out NULL
aggordered Boolean   If true, the aggregate is defined as ORDERED.
aggsortop oid pg_operator.oid Associated sort operator OID (zero if none)
aggtranstype oid pg_type.oid Data type of the aggregate function's internal transition (state) data
aggtransspace int4 pg_type.int4 Estimated size of state data (0 for default estimate)