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.
| column | type | references | description |
|---|---|---|---|
| aggfnoid | regproc | pg_proc.oid | Aggregate function OID |
| aggtransfn | regproc | pg_proc.oid | Transition function OID |
| aggprelimfn | regproc | Preliminary 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 | |
| agginvtransfn | regproc | pg_proc.oid | The OID in pg_proc of the inverse function of aggtransfn |
| agginvprelimfn | regproc | pg_proc.oid | The OID in pg_proc of the inverse function of aggprelimfn |
| 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 |