# 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 |	OID of the aggregate function
|`aggkind` |	char |		 |Aggregate kind: n for normal aggregates, o for ordered-set aggregates, or h for hypothetical-set aggregates
|`aggnumdirectargs` |	smallint |		 |Number of direct (non-aggregated) arguments of an ordered-set or hypothetical-set aggregate, counting a variadic array as one argument. If equal to `pronargs`, the aggregate must be variadic and the variadic array describes the aggregated arguments as well as the final direct arguments. Always zero for normal aggregates.
|`aggtransfn` |	regproc |	pg_proc.oid |	Transition function OID
|`aggfinalfn` |	regproc |	pg_proc.oid	 |Final function OID (zero if none)
|`aggcombinefn` |	regproc |	pg_proc.oid	 |Combine function OID (zero if none)
|`aggserialfn` |	regproc |	pg_proc.oid	 |OID of the serialization function to convert transtype to `bytea` (zero if none)
|`aggdeserialfn` |	regproc |	pg_proc.oid	 |OID of the deserialization function to convert `bytea` to transtype (zero if none)
|`aggmtransfn` |	regproc |	pg_proc.oid	 |Forward transition function OID for moving-aggregate mode (zero if none)
|`aggminvtransfn` |	regproc |	pg_proc.oid |	Inverse transition function OID for moving-aggregate mode (zero if none)
|`aggmfinalfn` |	regproc |	pg_proc.oid	 |Final function OID for moving-aggregate mode (zero if none)
|`aggfinalextra` |	bool |		 |True to pass extra dummy arguments to `aggfinalfn`
|`aggmfinalextra` |	bool |		 |True to pass extra dummy arguments to `aggmfinalfn`
|`aggfinalmodify` |	char |		 |Indicates whether `aggfinalfn` modifies the transition state
|`aggmfinalmodify` |	char |		 |Indicates whether `aggmfinalfn` modifies the transition state
|`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` |	integer |		 |Approximate average size (in bytes) of the transition state data, or zero to use a default estimate
|`aggmtranstype` |	oid |	pg_type.oid	 |Data type of the aggregate function's internal transition (state) data for moving-aggregate mode (zero if none)
|`aggmtransspace` |	integer |		 |Approximate average size (in bytes) of the transition state data for moving-aggregate mode, or zero to use a default estimate
|`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.
|`aggminitval` |	text |		 |The initial value of the transition state for moving- aggregate mode. 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.
|`aggrepsafeexec` |	bool |		 |True to specify that the aggregate can be safely executed on replicated slices. An order-agnostic aggregate would be considered safe in this context.