| --- |
| title: pg_aggregate |
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| 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. |
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| <a id="topic1__fu141982"></a> |
| <span class="tablecap">Table 1. pg\_catalog.pg\_aggregate</span> |
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| | 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 | |
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