PostgreSQL specific aggregation functions¶
These functions are available from the django.contrib.postgres.aggregates
module. They are described in more detail in the PostgreSQL docs.
Note
All functions come without default aliases, so you must explicitly provide one. For example:
>>> SomeModel.objects.aggregate(arr=ArrayAgg('somefield'))
{'arr': [0, 1, 2]}
Generalpurpose aggregation functions¶
ArrayAgg
¶

class
ArrayAgg
(expression, distinct=False, filter=None, ordering=(), **extra)¶ Returns a list of values, including nulls, concatenated into an array.

distinct
¶ An optional boolean argument that determines if array values will be distinct. Defaults to
False
.

ordering
¶ An optional string of a field name (with an optional
""
prefix which indicates descending order) or an expression (or a tuple or list of strings and/or expressions) that specifies the ordering of the elements in the result list.Examples:
'some_field' 'some_field' from django.db.models import F F('some_field').desc()

BitAnd
¶

class
BitAnd
(expression, filter=None, **extra)¶ Returns an
int
of the bitwiseAND
of all nonnull input values, orNone
if all values are null.
BitOr
¶

class
BitOr
(expression, filter=None, **extra)¶ Returns an
int
of the bitwiseOR
of all nonnull input values, orNone
if all values are null.
BoolAnd
¶

class
BoolAnd
(expression, filter=None, **extra)¶ Returns
True
, if all input values are true,None
if all values are null or if there are no values, otherwiseFalse
.
BoolOr
¶

class
BoolOr
(expression, filter=None, **extra)¶ Returns
True
if at least one input value is true,None
if all values are null or if there are no values, otherwiseFalse
.
JSONBAgg
¶

class
JSONBAgg
(expressions, filter=None, ordering=(), **extra)¶ Returns the input values as a
JSON
array.
ordering
¶  New in Django Development version.
An optional string of a field name (with an optional
""
prefix which indicates descending order) or an expression (or a tuple or list of strings and/or expressions) that specifies the ordering of the elements in the result list.Examples are the same as for
ArrayAgg.ordering
.

StringAgg
¶

class
StringAgg
(expression, delimiter, distinct=False, filter=None, ordering=())¶ Returns the input values concatenated into a string, separated by the
delimiter
string.
delimiter
¶ Required argument. Needs to be a string.

distinct
¶ An optional boolean argument that determines if concatenated values will be distinct. Defaults to
False
.

ordering
¶ An optional string of a field name (with an optional
""
prefix which indicates descending order) or an expression (or a tuple or list of strings and/or expressions) that specifies the ordering of the elements in the result string.Examples are the same as for
ArrayAgg.ordering
.

Aggregate functions for statistics¶
y
and x
¶
The arguments y
and x
for all these functions can be the name of a
field or an expression returning a numeric data. Both are required.
Corr
¶

class
Corr
(y, x, filter=None)¶ Returns the correlation coefficient as a
float
, orNone
if there aren’t any matching rows.
CovarPop
¶

class
CovarPop
(y, x, sample=False, filter=None)¶ Returns the population covariance as a
float
, orNone
if there aren’t any matching rows.Has one optional argument:

sample
¶ By default
CovarPop
returns the general population covariance. However, ifsample=True
, the return value will be the sample population covariance.

RegrAvgX
¶

class
RegrAvgX
(y, x, filter=None)¶ Returns the average of the independent variable (
sum(x)/N
) as afloat
, orNone
if there aren’t any matching rows.
RegrAvgY
¶

class
RegrAvgY
(y, x, filter=None)¶ Returns the average of the dependent variable (
sum(y)/N
) as afloat
, orNone
if there aren’t any matching rows.
RegrCount
¶

class
RegrCount
(y, x, filter=None)¶ Returns an
int
of the number of input rows in which both expressions are not null.
RegrIntercept
¶

class
RegrIntercept
(y, x, filter=None)¶ Returns the yintercept of the leastsquaresfit linear equation determined by the
(x, y)
pairs as afloat
, orNone
if there aren’t any matching rows.
RegrR2
¶

class
RegrR2
(y, x, filter=None)¶ Returns the square of the correlation coefficient as a
float
, orNone
if there aren’t any matching rows.
RegrSlope
¶

class
RegrSlope
(y, x, filter=None)¶ Returns the slope of the leastsquaresfit linear equation determined by the
(x, y)
pairs as afloat
, orNone
if there aren’t any matching rows.
RegrSXX
¶

class
RegrSXX
(y, x, filter=None)¶ Returns
sum(x^2)  sum(x)^2/N
(“sum of squares” of the independent variable) as afloat
, orNone
if there aren’t any matching rows.
Usage examples¶
We will use this example table:
 FIELD1  FIELD2  FIELD3 

 foo  1  13 
 bar  2  (null) 
 test  3  13 
Here’s some examples of some of the generalpurpose aggregation functions:
>>> TestModel.objects.aggregate(result=StringAgg('field1', delimiter=';'))
{'result': 'foo;bar;test'}
>>> TestModel.objects.aggregate(result=ArrayAgg('field2'))
{'result': [1, 2, 3]}
>>> TestModel.objects.aggregate(result=ArrayAgg('field1'))
{'result': ['foo', 'bar', 'test']}
The next example shows the usage of statistical aggregate functions. The underlying math will be not described (you can read about this, for example, at wikipedia):
>>> TestModel.objects.aggregate(count=RegrCount(y='field3', x='field2'))
{'count': 2}
>>> TestModel.objects.aggregate(avgx=RegrAvgX(y='field3', x='field2'),
... avgy=RegrAvgY(y='field3', x='field2'))
{'avgx': 2, 'avgy': 13}