Release: 1.0.0 | Release Date: Not released

SQLAlchemy 1.0 Documentation

SQL and Generic Functions

SQL functions which are known to SQLAlchemy with regards to database-specific rendering, return types and argument behavior. Generic functions are invoked like all SQL functions, using the func attribute:

select([func.count()]).select_from(sometable)

Note that any name not known to func generates the function name as is - there is no restriction on what SQL functions can be called, known or unknown to SQLAlchemy, built-in or user defined. The section here only describes those functions where SQLAlchemy already knows what argument and return types are in use.

SQL function API, factories, and built-in functions.

class sqlalchemy.sql.functions.AnsiFunction(**kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

identifier = 'AnsiFunction'
name = 'AnsiFunction'
class sqlalchemy.sql.functions.Function(name, *clauses, **kw)

Bases: sqlalchemy.sql.functions.FunctionElement

Describe a named SQL function.

See the superclass FunctionElement for a description of public methods.

See also

func - namespace which produces registered or ad-hoc Function instances.

GenericFunction - allows creation of registered function types.

__init__(name, *clauses, **kw)

Construct a Function.

The func construct is normally used to construct new Function instances.

class sqlalchemy.sql.functions.FunctionElement(*clauses, **kwargs)

Bases: sqlalchemy.sql.expression.Executable, sqlalchemy.sql.expression.ColumnElement, sqlalchemy.sql.expression.FromClause

Base for SQL function-oriented constructs.

See also

Function - named SQL function.

func - namespace which produces registered or ad-hoc Function instances.

GenericFunction - allows creation of registered function types.

__init__(*clauses, **kwargs)

Construct a FunctionElement.

alias(name=None, flat=False)

Produce a Alias construct against this FunctionElement.

This construct wraps the function in a named alias which is suitable for the FROM clause.

e.g.:

from sqlalchemy.sql import column

stmt = select([column('data')]).select_from(
    func.unnest(Table.data).alias('data_view')
)

Would produce:

SELECT data
FROM unnest(sometable.data) AS data_view

New in version 0.9.8: The FunctionElement.alias() method is now supported. Previously, this method’s behavior was undefined and did not behave consistently across versions.

clauses

Return the underlying ClauseList which contains the arguments for this FunctionElement.

columns

The set of columns exported by this FunctionElement.

Function objects currently have no result column names built in; this method returns a single-element column collection with an anonymously named column.

An interim approach to providing named columns for a function as a FROM clause is to build a select() with the desired columns:

from sqlalchemy.sql import column

stmt = select([column('x'), column('y')]).                select_from(func.myfunction())
execute()

Execute this FunctionElement against an embedded ‘bind’.

This first calls select() to produce a SELECT construct.

Note that FunctionElement can be passed to the Connectable.execute() method of Connection or Engine.

filter(*criterion)

Produce a FILTER clause against this function.

Used against aggregate and window functions, for database backends that support the “FILTER” clause.

The expression:

func.count(1).filter(True)

is shorthand for:

from sqlalchemy import funcfilter
funcfilter(func.count(1), True)

New in version 1.0.0.

get_children(**kwargs)
over(partition_by=None, order_by=None)

Produce an OVER clause against this function.

Used against aggregate or so-called “window” functions, for database backends that support window functions.

The expression:

func.row_number().over(order_by='x')

is shorthand for:

from sqlalchemy import over
over(func.row_number(), order_by='x')

See over() for a full description.

New in version 0.7.

packagenames = ()
scalar()

Execute this FunctionElement against an embedded ‘bind’ and return a scalar value.

This first calls select() to produce a SELECT construct.

Note that FunctionElement can be passed to the Connectable.scalar() method of Connection or Engine.

select()

Produce a select() construct against this FunctionElement.

This is shorthand for:

s = select([function_element])
class sqlalchemy.sql.functions.GenericFunction(*args, **kwargs)

Bases: sqlalchemy.sql.functions.Function

Define a ‘generic’ function.

A generic function is a pre-established Function class that is instantiated automatically when called by name from the func attribute. Note that calling any name from func has the effect that a new Function instance is created automatically, given that name. The primary use case for defining a GenericFunction class is so that a function of a particular name may be given a fixed return type. It can also include custom argument parsing schemes as well as additional methods.

Subclasses of GenericFunction are automatically registered under the name of the class. For example, a user-defined function as_utc() would be available immediately:

from sqlalchemy.sql.functions import GenericFunction
from sqlalchemy.types import DateTime

class as_utc(GenericFunction):
    type = DateTime

print select([func.as_utc()])

User-defined generic functions can be organized into packages by specifying the “package” attribute when defining GenericFunction. Third party libraries containing many functions may want to use this in order to avoid name conflicts with other systems. For example, if our as_utc() function were part of a package “time”:

class as_utc(GenericFunction):
    type = DateTime
    package = "time"

The above function would be available from func using the package name time:

print select([func.time.as_utc()])

A final option is to allow the function to be accessed from one name in func but to render as a different name. The identifier attribute will override the name used to access the function as loaded from func, but will retain the usage of name as the rendered name:

class GeoBuffer(GenericFunction):
    type = Geometry
    package = "geo"
    name = "ST_Buffer"
    identifier = "buffer"

The above function will render as follows:

>>> print func.geo.buffer()
ST_Buffer()

New in version 0.8: GenericFunction now supports automatic registration of new functions as well as package and custom naming support.

Changed in version 0.8: The attribute name type is used to specify the function’s return type at the class level. Previously, the name __return_type__ was used. This name is still recognized for backwards-compatibility.

coerce_arguments = True
identifier = 'GenericFunction'
name = 'GenericFunction'
class sqlalchemy.sql.functions.ReturnTypeFromArgs(*args, **kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

Define a function whose return type is the same as its arguments.

identifier = 'ReturnTypeFromArgs'
name = 'ReturnTypeFromArgs'
class sqlalchemy.sql.functions.char_length(arg, **kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

identifier = 'char_length'
name = 'char_length'
type

alias of Integer

class sqlalchemy.sql.functions.coalesce(*args, **kwargs)

Bases: sqlalchemy.sql.functions.ReturnTypeFromArgs

identifier = 'coalesce'
name = 'coalesce'
class sqlalchemy.sql.functions.concat(*args, **kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

identifier = 'concat'
name = 'concat'
type

alias of String

class sqlalchemy.sql.functions.count(expression=None, **kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

The ANSI COUNT aggregate function. With no arguments, emits COUNT *.

identifier = 'count'
name = 'count'
type

alias of Integer

class sqlalchemy.sql.functions.current_date(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'current_date'
name = 'current_date'
type

alias of Date

class sqlalchemy.sql.functions.current_time(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'current_time'
name = 'current_time'
type

alias of Time

class sqlalchemy.sql.functions.current_timestamp(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'current_timestamp'
name = 'current_timestamp'
type

alias of DateTime

class sqlalchemy.sql.functions.current_user(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'current_user'
name = 'current_user'
type

alias of String

sqlalchemy.sql.functions.func = <sqlalchemy.sql.functions._FunctionGenerator object at 0x7f3187b260d0>

Generate SQL function expressions.

func is a special object instance which generates SQL functions based on name-based attributes, e.g.:

>>> print func.count(1)
count(:param_1)

The element is a column-oriented SQL element like any other, and is used in that way:

>>> print select([func.count(table.c.id)])
SELECT count(sometable.id) FROM sometable

Any name can be given to func. If the function name is unknown to SQLAlchemy, it will be rendered exactly as is. For common SQL functions which SQLAlchemy is aware of, the name may be interpreted as a generic function which will be compiled appropriately to the target database:

>>> print func.current_timestamp()
CURRENT_TIMESTAMP

To call functions which are present in dot-separated packages, specify them in the same manner:

>>> print func.stats.yield_curve(5, 10)
stats.yield_curve(:yield_curve_1, :yield_curve_2)

SQLAlchemy can be made aware of the return type of functions to enable type-specific lexical and result-based behavior. For example, to ensure that a string-based function returns a Unicode value and is similarly treated as a string in expressions, specify Unicode as the type:

>>> print func.my_string(u'hi', type_=Unicode) + ' ' + \
... func.my_string(u'there', type_=Unicode)
my_string(:my_string_1) || :my_string_2 || my_string(:my_string_3)

The object returned by a func call is usually an instance of Function. This object meets the “column” interface, including comparison and labeling functions. The object can also be passed the execute() method of a Connection or Engine, where it will be wrapped inside of a SELECT statement first:

print connection.execute(func.current_timestamp()).scalar()

In a few exception cases, the func accessor will redirect a name to a built-in expression such as cast() or extract(), as these names have well-known meaning but are not exactly the same as “functions” from a SQLAlchemy perspective.

New in version 0.8: func can return non-function expression constructs for common quasi-functional names like cast() and extract().

Functions which are interpreted as “generic” functions know how to calculate their return type automatically. For a listing of known generic functions, see SQL and Generic Functions.

Note

The func construct has only limited support for calling standalone “stored procedures”, especially those with special parameterization concerns.

See the section Calling Stored Procedures for details on how to use the DBAPI-level callproc() method for fully traditional stored procedures.

class sqlalchemy.sql.functions.localtime(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'localtime'
name = 'localtime'
type

alias of DateTime

class sqlalchemy.sql.functions.localtimestamp(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'localtimestamp'
name = 'localtimestamp'
type

alias of DateTime

class sqlalchemy.sql.functions.max(*args, **kwargs)

Bases: sqlalchemy.sql.functions.ReturnTypeFromArgs

identifier = 'max'
name = 'max'
class sqlalchemy.sql.functions.min(*args, **kwargs)

Bases: sqlalchemy.sql.functions.ReturnTypeFromArgs

identifier = 'min'
name = 'min'
class sqlalchemy.sql.functions.next_value(seq, **kw)

Bases: sqlalchemy.sql.functions.GenericFunction

Represent the ‘next value’, given a Sequence as its single argument.

Compiles into the appropriate function on each backend, or will raise NotImplementedError if used on a backend that does not provide support for sequences.

identifier = 'next_value'
name = 'next_value'
type = Integer()
class sqlalchemy.sql.functions.now(*args, **kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

identifier = 'now'
name = 'now'
type

alias of DateTime

class sqlalchemy.sql.functions.random(*args, **kwargs)

Bases: sqlalchemy.sql.functions.GenericFunction

identifier = 'random'
name = 'random'
sqlalchemy.sql.functions.register_function(identifier, fn, package='_default')

Associate a callable with a particular func. name.

This is normally called by _GenericMeta, but is also available by itself so that a non-Function construct can be associated with the func accessor (i.e. CAST, EXTRACT).

class sqlalchemy.sql.functions.session_user(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'session_user'
name = 'session_user'
type

alias of String

class sqlalchemy.sql.functions.sum(*args, **kwargs)

Bases: sqlalchemy.sql.functions.ReturnTypeFromArgs

identifier = 'sum'
name = 'sum'
class sqlalchemy.sql.functions.sysdate(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'sysdate'
name = 'sysdate'
type

alias of DateTime

class sqlalchemy.sql.functions.user(**kwargs)

Bases: sqlalchemy.sql.functions.AnsiFunction

identifier = 'user'
name = 'user'
type

alias of String