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.