sqlalchemy.sql.functions.GenericFunction

class documentation

class GenericFunction(util.with_metaclass(_GenericMeta, Function)):

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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
    inherit_cache = True

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"
    inherit_cache = True

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"
    inherit_cache = True

The above function will render as follows:

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

The name will be rendered as is, however without quoting unless the name contains special characters that require quoting. To force quoting on or off for the name, use the .sqlalchemy.sql.quoted_name construct:

from sqlalchemy.sql import quoted_name

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

The above function will render as:

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

New in version 1.3.13: The .quoted_name construct is now recognized for quoting when used with the "name" attribute of the object, so that quoting can be forced on or off for the function name.

Method	`__init__`	Undocumented
Class Variable	`_register`	Undocumented
Class Variable	`coerce_arguments`	Undocumented
Class Variable	`inherit_cache`	Undocumented
Instance Variable	`_bind`	Undocumented
Instance Variable	`_has_args`	Undocumented
Instance Variable	`clause_expr`	Undocumented
Instance Variable	`packagenames`	Undocumented
Instance Variable	`type`	Undocumented

def __init__(self, *args, **kwargs):

overridden in sqlalchemy.sql.functions.AnsiFunction, sqlalchemy.sql.functions.array_agg, sqlalchemy.sql.functions.char_length, sqlalchemy.sql.functions.count, sqlalchemy.sql.functions.next_value, sqlalchemy.sql.functions.ReturnTypeFromArgs

Undocumented

_register: bool =

Undocumented

coerce_arguments: bool =

Undocumented

inherit_cache: bool =

overridden in sqlalchemy.dialects.postgresql.hstore.hstore, sqlalchemy.sql.functions.AnsiFunction, sqlalchemy.sql.functions.array_agg, sqlalchemy.sql.functions.char_length, sqlalchemy.sql.functions.concat, sqlalchemy.sql.functions.count, sqlalchemy.sql.functions.cube, sqlalchemy.sql.functions.cume_dist, sqlalchemy.sql.functions.dense_rank, sqlalchemy.sql.functions.grouping_sets, sqlalchemy.sql.functions.now, sqlalchemy.sql.functions.OrderedSetAgg, sqlalchemy.sql.functions.percent_rank, sqlalchemy.sql.functions.random, sqlalchemy.sql.functions.rank, sqlalchemy.sql.functions.ReturnTypeFromArgs, sqlalchemy.sql.functions.rollup, sqlalchemy.dialects.postgresql.hstore._HStoreArrayFunction, sqlalchemy.dialects.postgresql.hstore._HStoreDefinedFunction, sqlalchemy.dialects.postgresql.hstore._HStoreDeleteFunction, sqlalchemy.dialects.postgresql.hstore._HStoreKeysFunction, sqlalchemy.dialects.postgresql.hstore._HStoreMatrixFunction, sqlalchemy.dialects.postgresql.hstore._HStoreSliceFunction, sqlalchemy.dialects.postgresql.hstore._HStoreValsFunction

Undocumented

_bind =

overridden in sqlalchemy.sql.functions.next_value

Undocumented

_has_args =

overridden in sqlalchemy.sql.functions.coalesce, sqlalchemy.sql.functions.cube, sqlalchemy.sql.functions.grouping_sets, sqlalchemy.sql.functions.random, sqlalchemy.sql.functions.rollup

Undocumented

clause_expr =

Undocumented

packagenames: tuple =

Undocumented

type =

overridden in sqlalchemy.sql.functions.cume_dist, sqlalchemy.sql.functions.dense_rank, sqlalchemy.sql.functions.next_value, sqlalchemy.sql.functions.percent_rank, sqlalchemy.sql.functions.rank, sqlalchemy.dialects.postgresql.hstore._HStoreArrayFunction, sqlalchemy.dialects.postgresql.hstore._HStoreKeysFunction, sqlalchemy.dialects.postgresql.hstore._HStoreMatrixFunction, sqlalchemy.dialects.postgresql.hstore._HStoreValsFunction

Undocumented