PostgreSQL

51.2. `pg_aggregate`
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51.2. `pg_aggregate`

The catalog pg_aggregate 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 51.2. pg_aggregate Columns

Name Type References Description

Name	Type	References	Description
`aggfnoid`	`regproc`	`pg_proc.oid`	`pg_proc` OID of the aggregate function
`aggkind`	`char`		Aggregate kind: `n` for “[.quote]#normal”# aggregates, `o` for “[.quote]#ordered-set”# aggregates, or `h` for “[.quote]#hypothetical-set”# aggregates
`aggnumdirectargs`	`int2`		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
`aggfinalfn`	`regproc`	`pg_proc.oid`	Final function (zero if none)
`aggcombinefn`	`regproc`	`pg_proc.oid`	Combine function (zero if none)
`aggserialfn`	`regproc`	`pg_proc.oid`	Serialization function (zero if none)
`aggdeserialfn`	`regproc`	`pg_proc.oid`	Deserialization function (zero if none)
`aggmtransfn`	`regproc`	`pg_proc.oid`	Forward transition function for moving-aggregate mode (zero if none)
`aggminvtransfn`	`regproc`	`pg_proc.oid`	Inverse transition function for moving-aggregate mode (zero if none)
`aggmfinalfn`	`regproc`	`pg_proc.oid`	Final function 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`
`aggsortop`	`oid`	`pg_operator.oid`	Associated sort operator (zero if none)
`aggtranstype`	`oid`	`pg_type.oid`	Data type of the aggregate function’s internal transition (state) data
`aggtransspace`	`int4`		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`	`int4`		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.

aggfnoid

regproc

pg_proc.oid

pg_proc OID of the aggregate function

aggkind

char

Aggregate kind: n for “[.quote]#normal”# aggregates, o for “[.quote]#ordered-set”# aggregates, or h for “[.quote]#hypothetical-set”# aggregates

aggnumdirectargs

int2

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

aggfinalfn

regproc

pg_proc.oid

Final function (zero if none)

aggcombinefn

regproc

pg_proc.oid

Combine function (zero if none)

aggserialfn

regproc

pg_proc.oid

Serialization function (zero if none)

aggdeserialfn

regproc

pg_proc.oid

Deserialization function (zero if none)

aggmtransfn

regproc

pg_proc.oid

Forward transition function for moving-aggregate mode (zero if none)

aggminvtransfn

regproc

pg_proc.oid

Inverse transition function for moving-aggregate mode (zero if none)

aggmfinalfn

regproc

pg_proc.oid

Final function 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

aggsortop

oid

pg_operator.oid

Associated sort operator (zero if none)

aggtranstype

oid

pg_type.oid

Data type of the aggregate function’s internal transition (state) data

aggtransspace

int4

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

int4

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.

New aggregate functions are registered with the CREATE AGGREGATE command. See Section 37.10 for more information about writing aggregate functions and the meaning of the transition functions, etc.

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51.2. pg_aggregate

51.2. `pg_aggregate`