# 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                                      |
| `agginvtransfn`  | regproc | pg_proc.oid     | The OID in pg_proc of the inverse function of *aggtransfn*   |
| `aggprelimfn`    | regproc |                 | Preliminary function OID (zero if none)                      |
| `agginvprelimfn` | regproc | pg_proc.oid     | The OID in pg_proc of the inverse function of aggprelimfn    |
| `aggfinalfn`     | regproc | pg_proc.oid     | Final function OID (zero if none)                            |
| `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 |
| `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`.            |