Customizing DDL¶
これまでのセクションでは、 Table
、 ForeignKeyConstraint
、 CheckConstraint
、および Sequence
など、さまざまなスキーマ構成体について説明してきました。これまでずっと、 Table
および MetaData
の create()
および create_all()
メソッドを利用して、すべての構成体に対してデータ定義言語(DDL)を発行してきました。発行されると、事前に決定された操作の順序が呼び出され、各テーブルを作成するためのDDLが、すべての制約とそれに関連付けられた他のオブジェクトを含めて無条件に作成されます。データベース固有のDDLが必要とされるより複雑なシナリオでは、SQLAlchemyは、テーブルの標準生成に付随して、またはそれ自体で、任意の条件に基づいて任意のDDLを追加するために使用できる2つの手法を提供します。
Custom DDL¶
カスタムDDLフレーズは、 DDL
構文を使うと簡単に実現できます。この構文は他のDDL要素と同じように動作しますが、出力されるテキストである文字列を受け付ける点が異なります:
event.listen(
metadata,
"after_create",
DDL(
"ALTER TABLE users ADD CONSTRAINT "
"cst_user_name_length "
" CHECK (length(user_name) >= 8)"
),
)
DDL構文のライブラリを作成するより包括的な方法は、カスタムコンパイルを使用することです。詳細は Custom SQL Constructs and Compilation Extension を参照してください:
Controlling DDL Sequences¶
前に紹介した DDL
構文にも、データベースの検査に基づいて条件付きで呼び出す機能があります。この機能は ExecutableDDLElement.execute_if()
メソッドを使用して利用できます。例えば、PostgreSQLバックエンド上でのみトリガを作成したい場合、次のように呼び出すことができます:
mytable = Table(
"mytable",
metadata,
Column("id", Integer, primary_key=True),
Column("data", String(50)),
)
func = DDL(
"CREATE FUNCTION my_func() "
"RETURNS TRIGGER AS $$ "
"BEGIN "
"NEW.data := 'ins'; "
"RETURN NEW; "
"END; $$ LANGUAGE PLPGSQL"
)
trigger = DDL(
"CREATE TRIGGER dt_ins BEFORE INSERT ON mytable "
"FOR EACH ROW EXECUTE PROCEDURE my_func();"
)
event.listen(mytable, "after_create", func.execute_if(dialect="postgresql"))
event.listen(mytable, "after_create", trigger.execute_if(dialect="postgresql"))
ExecutableDDLElement.execute_if.dialect
キーワードは、タプルの文字列のダイアレクト名も受け付けます:
event.listen(
mytable, "after_create", trigger.execute_if(dialect=("postgresql", "mysql"))
)
event.listen(
mytable, "before_drop", trigger.execute_if(dialect=("postgresql", "mysql"))
)
ExecutableDDLElement.execute_if()
メソッドは、使用中のデータベース接続を受け取る呼び出し可能な関数に対しても動作します。以下の例では、これを使用して条件付きでCHECK制約を作成し、まずPostgreSQLカタログ内を調べて存在するかどうかを確認します:
def should_create(ddl, target, connection, **kw):
row = connection.execute(
"select conname from pg_constraint where conname='%s'" % ddl.element.name
).scalar()
return not bool(row)
def should_drop(ddl, target, connection, **kw):
return not should_create(ddl, target, connection, **kw)
event.listen(
users,
"after_create",
DDL(
"ALTER TABLE users ADD CONSTRAINT "
"cst_user_name_length CHECK (length(user_name) >= 8)"
).execute_if(callable_=should_create),
)
event.listen(
users,
"before_drop",
DDL("ALTER TABLE users DROP CONSTRAINT cst_user_name_length").execute_if(
callable_=should_drop
),
)
users.create(engine)
CREATE TABLE users (
user_id SERIAL NOT NULL,
user_name VARCHAR(40) NOT NULL,
PRIMARY KEY (user_id)
)
SELECT conname FROM pg_constraint WHERE conname='cst_user_name_length'
ALTER TABLE users ADD CONSTRAINT cst_user_name_length CHECK (length(user_name) >= 8)
users.drop(engine)
SELECT conname FROM pg_constraint WHERE conname='cst_user_name_length'
ALTER TABLE users DROP CONSTRAINT cst_user_name_length
DROP TABLE users
Using the built-in DDLElement Classes¶
sqlalchemy.schema
パッケージには、DDL式を提供するSQL式の構成体が含まれています。これらはすべて、共通のベース ExecutableDDLElement
から拡張されています。例えば、 CreateTable
文を生成するには、 CreateTable
構成体を使用できます。
from sqlalchemy.schema import CreateTable
with engine.connect() as conn:
conn.execute(CreateTable(mytable))
CREATE TABLE mytable (
col1 INTEGER,
col2 INTEGER,
col3 INTEGER,
col4 INTEGER,
col5 INTEGER,
col6 INTEGER
)
上記の CreateTable
構文は、他の式構文(例えば select()
や table.insert()
など)と同じように動作します。SQLAlchemyのDDL指向の構文はすべて、 ExecutableDDLElement
基底クラスのサブクラスです。これは、CREATEやDROP、ALTERに対応するすべてのオブジェクトの基底であり、SQLAlchemyだけでなくAlembic Migrationsでも同様です。利用可能な構文の完全なリファレンスは DDL Expression Constructs API にあります。
ユーザ定義のDDL構文は、 ExecutableDDLElement
自身のサブクラスとして作成することもできます。 Custom SQL Constructs and Compilation Extension のドキュメントにいくつか例があります。
Controlling DDL Generation of Constraints and Indexes¶
New in version 2.0.
前述の ExecutableDDLElement.execute_if()
メソッドは、条件付きで呼び出す必要があるカスタムの DDL
クラスには便利ですが、特定の Table
に通常関連する要素、つまり制約とインデックスも、PostgreSQLやSQL Serverなどの特定のバックエンドに固有の機能を含むインデックスなどの”条件付き”ルールの対象にする必要があります。このユースケースでは、 Constraint.ddl_if()
メソッドと Index.ddl_if()
メソッドを CheckConstraint
、 UniqueConstraint
、 Index
などの構文に対して使用できます。 ExecutableDDLElement.execute_if()
メソッドと同じ引数を受け入れて、親の Table
オブジェクトに関してDDLが生成されるかどうかを制御します。これらのメソッドは、 Table
の定義を作成するときにインラインで使用できます。(または、ORM宣言型マッピングで __table_args__
コレクションを使用する場合も同様です)
たとえば:
from sqlalchemy import CheckConstraint, Index
from sqlalchemy import MetaData, Table, Column
from sqlalchemy import Integer, String
meta = MetaData()
my_table = Table(
"my_table",
meta,
Column("id", Integer, primary_key=True),
Column("num", Integer),
Column("data", String),
Index("my_pg_index", "data").ddl_if(dialect="postgresql"),
CheckConstraint("num > 5").ddl_if(dialect="postgresql"),
)
上の例では、 Table
構文は Index
と CheckConstraint
の両方を参照します。どちらも .ddl_if(dialect="postgresql")
を示します。これは、これらの要素がPostgreSQLダイアレクトに対してのみCREATE TABLEシーケンスに含まれることを示します。例えば、SQLiteダイアレクトに対して meta.create_all()
を実行しても、どちらの構文も含まれません。
>>> from sqlalchemy import create_engine
>>> sqlite_engine = create_engine("sqlite+pysqlite://", echo=True)
>>> meta.create_all(sqlite_engine)
BEGIN (implicit)
PRAGMA main.table_info("my_table")
[raw sql] ()
PRAGMA temp.table_info("my_table")
[raw sql] ()
CREATE TABLE my_table (
id INTEGER NOT NULL,
num INTEGER,
data VARCHAR,
PRIMARY KEY (id)
)
しかし、同じコマンドをPostgreSQLデータベースに対して実行すると、CHECK制約用のインラインDDLと、インデックス用に生成された別のCREATE文が表示されます。
>>> from sqlalchemy import create_engine
>>> postgresql_engine = create_engine(
... "postgresql+psycopg2://scott:tiger@localhost/test", echo=True
... )
>>> meta.create_all(postgresql_engine)
BEGIN (implicit)
select relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where pg_catalog.pg_table_is_visible(c.oid) and relname=%(name)s
[generated in 0.00009s] {'name': 'my_table'}
CREATE TABLE my_table (
id SERIAL NOT NULL,
num INTEGER,
data VARCHAR,
PRIMARY KEY (id),
CHECK (num > 5)
)
[no key 0.00007s] {}
CREATE INDEX my_pg_index ON my_table (data)
[no key 0.00013s] {}
COMMIT
Constraint.ddl_if()
および Index.ddl_if()
メソッドは、 ExecutableDDLElement.execute_if()
の動作のようにDDLの実行時だけでなく、 CreateTable
オブジェクトのSQLコンパイル時にも参照されるイベントフックを作成します。このオブジェクトは、CreateTableステートメント内のインラインで CHECK (num > 5)
DDLをレンダリングします。そのため、 ddl_if.callable_()
パラメータが受け取るイベントフックには、より豊富な引数セットが存在します。これには、 dialect
キーワード引数が渡されることや、シーケンスの”インラインレンダリング”部分の compiler
キーワード引数を介して DDLCompiler
のインスタンスが渡されることなどが含まれます。 bind
引数は、イベントが DDLCompiler
シーケンス内でトリガされるときには 存在しない ので、データベースのバージョン情報を検査しようとする最新のイベントフックは、PostgreSQLのバージョン情報をテストするなど、与えられた Dialect
オブジェクトを使用するのが最適です。
def only_pg_14(ddl_element, target, bind, dialect, **kw):
return dialect.name == "postgresql" and dialect.server_version_info >= (14,)
my_table = Table(
"my_table",
meta,
Column("id", Integer, primary_key=True),
Column("num", Integer),
Column("data", String),
Index("my_pg_index", "data").ddl_if(callable_=only_pg_14),
)
DDL Expression Constructs API¶
Object Name | Description |
---|---|
Base class for DDL constructs that represent CREATE and DROP or equivalents. |
|
Represent an ALTER TABLE ADD CONSTRAINT statement. |
|
The root of DDL constructs, including those that are sub-elements within the “create table” and other processes. |
|
Represent a |
|
Represent a CREATE INDEX statement. |
|
Represent a CREATE SCHEMA statement. |
|
Represent a CREATE SEQUENCE statement. |
|
Represent a CREATE TABLE statement. |
|
A literal DDL statement. |
|
Represent an ALTER TABLE DROP CONSTRAINT statement. |
|
Represent a DROP INDEX statement. |
|
Represent a DROP SCHEMA statement. |
|
Represent a DROP SEQUENCE statement. |
|
Represent a DROP TABLE statement. |
|
Base class for standalone executable DDL expression constructs. |
|
sort_tables(tables[, skip_fn, extra_dependencies]) |
Sort a collection of |
sort_tables_and_constraints(tables[, filter_fn, extra_dependencies, _warn_for_cycles]) |
Sort a collection of |
- function sqlalchemy.schema.sort_tables(tables: Iterable[TableClause], skip_fn: Callable[[ForeignKeyConstraint], bool] | None = None, extra_dependencies: typing_Sequence[Tuple[TableClause, TableClause]] | None = None) List[Table] ¶
Sort a collection of
Table
objects based on dependency.This is a dependency-ordered sort which will emit
Table
objects such that they will follow their dependentTable
objects. Tables are dependent on another based on the presence ofForeignKeyConstraint
objects as well as explicit dependencies added byTable.add_is_dependent_on()
.Warning
The
sort_tables()
function cannot by itself accommodate automatic resolution of dependency cycles between tables, which are usually caused by mutually dependent foreign key constraints. When these cycles are detected, the foreign keys of these tables are omitted from consideration in the sort. A warning is emitted when this condition occurs, which will be an exception raise in a future release. Tables which are not part of the cycle will still be returned in dependency order.To resolve these cycles, the
ForeignKeyConstraint.use_alter
parameter may be applied to those constraints which create a cycle. Alternatively, thesort_tables_and_constraints()
function will automatically return foreign key constraints in a separate collection when cycles are detected so that they may be applied to a schema separately.Changed in version 1.3.17: - a warning is emitted when
sort_tables()
cannot perform a proper sort due to cyclical dependencies. This will be an exception in a future release. Additionally, the sort will continue to return other tables not involved in the cycle in dependency order which was not the case previously.- Parameters:
skip_fn¶ – optional callable which will be passed a
ForeignKeyConstraint
object; if it returns True, this constraint will not be considered as a dependency. Note this is different from the same parameter insort_tables_and_constraints()
, which is instead passed the owningForeignKeyConstraint
object.extra_dependencies¶ – a sequence of 2-tuples of tables which will also be considered as dependent on each other.
- function sqlalchemy.schema.sort_tables_and_constraints(tables, filter_fn=None, extra_dependencies=None, _warn_for_cycles=False)¶
Sort a collection of
Table
/ForeignKeyConstraint
objects.This is a dependency-ordered sort which will emit tuples of
(Table, [ForeignKeyConstraint, ...])
such that eachTable
follows its dependentTable
objects. RemainingForeignKeyConstraint
objects that are separate due to dependency rules not satisfied by the sort are emitted afterwards as(None, [ForeignKeyConstraint ...])
.Tables are dependent on another based on the presence of
ForeignKeyConstraint
objects, explicit dependencies added byTable.add_is_dependent_on()
, as well as dependencies stated here using thesort_tables_and_constraints.skip_fn
and/orsort_tables_and_constraints.extra_dependencies
parameters.- Parameters:
filter_fn¶ – optional callable which will be passed a
ForeignKeyConstraint
object, and returns a value based on whether this constraint should definitely be included or excluded as an inline constraint, or neither. If it returns False, the constraint will definitely be included as a dependency that cannot be subject to ALTER; if True, it will only be included as an ALTER result at the end. Returning None means the constraint is included in the table-based result unless it is detected as part of a dependency cycle.extra_dependencies¶ – a sequence of 2-tuples of tables which will also be considered as dependent on each other.
See also
- class sqlalchemy.schema.BaseDDLElement¶
The root of DDL constructs, including those that are sub-elements within the “create table” and other processes.
New in version 2.0.
Class signature
class
sqlalchemy.schema.BaseDDLElement
(sqlalchemy.sql.expression.ClauseElement
)
- class sqlalchemy.schema.ExecutableDDLElement¶
Base class for standalone executable DDL expression constructs.
This class is the base for the general purpose
DDL
class, as well as the various create/drop clause constructs such asCreateTable
,DropTable
,AddConstraint
, etc.Changed in version 2.0:
ExecutableDDLElement
is renamed fromDDLElement
, which still exists for backwards compatibility.ExecutableDDLElement
integrates closely with SQLAlchemy events, introduced in Events. An instance of one is itself an event receiving callable:event.listen( users, 'after_create', AddConstraint(constraint).execute_if(dialect='postgresql') )
Members
Class signature
class
sqlalchemy.schema.ExecutableDDLElement
(sqlalchemy.sql.roles.DDLRole
,sqlalchemy.sql.expression.Executable
,sqlalchemy.schema.BaseDDLElement
)-
method
sqlalchemy.schema.ExecutableDDLElement.
__call__(target, bind, **kw)¶ Execute the DDL as a ddl_listener.
-
method
sqlalchemy.schema.ExecutableDDLElement.
against(target: SchemaItem) Self ¶ Return a copy of this
ExecutableDDLElement
which will include the given target.This essentially applies the given item to the
.target
attribute of the returnedExecutableDDLElement
object. This target is then usable by event handlers and compilation routines in order to provide services such as tokenization of a DDL string in terms of a particularTable
.When a
ExecutableDDLElement
object is established as an event handler for theDDLEvents.before_create()
orDDLEvents.after_create()
events, and the event then occurs for a given target such as aConstraint
orTable
, that target is established with a copy of theExecutableDDLElement
object using this method, which then proceeds to theExecutableDDLElement.execute()
method in order to invoke the actual DDL instruction.- Parameters:
target¶ – a
SchemaItem
that will be the subject of a DDL operation.- Returns:
a copy of this
ExecutableDDLElement
with the.target
attribute assigned to the givenSchemaItem
.
See also
DDL
- uses tokenization against the “target” when processing the DDL string.
-
method
sqlalchemy.schema.ExecutableDDLElement.
execute_if(dialect: str | None = None, callable_: DDLIfCallable | None = None, state: Any | None = None) Self ¶ Return a callable that will execute this
ExecutableDDLElement
conditionally within an event handler.Used to provide a wrapper for event listening:
event.listen( metadata, 'before_create', DDL("my_ddl").execute_if(dialect='postgresql') )
- Parameters:
dialect¶ –
May be a string or tuple of strings. If a string, it will be compared to the name of the executing database dialect:
DDL('something').execute_if(dialect='postgresql')
If a tuple, specifies multiple dialect names:
DDL('something').execute_if(dialect=('postgresql', 'mysql'))
callable_¶ –
A callable, which will be invoked with three positional arguments as well as optional keyword arguments:
- ddl:
This DDL element.
- target:
The
Table
orMetaData
object which is the target of this event. May be None if the DDL is executed explicitly.- bind:
The
Connection
being used for DDL execution. May be None if this construct is being created inline within a table, in which casecompiler
will be present.- tables:
Optional keyword argument - a list of Table objects which are to be created/ dropped within a MetaData.create_all() or drop_all() method call.
- dialect:
keyword argument, but always present - the
Dialect
involved in the operation.- compiler:
keyword argument. Will be
None
for an engine level DDL invocation, but will refer to aDDLCompiler
if this DDL element is being created inline within a table.- state:
Optional keyword argument - will be the
state
argument passed to this function.- checkfirst:
Keyword argument, will be True if the ‘checkfirst’ flag was set during the call to
create()
,create_all()
,drop()
,drop_all()
.
If the callable returns a True value, the DDL statement will be executed.
state¶ – any value which will be passed to the callable_ as the
state
keyword argument.
-
method
- class sqlalchemy.schema.DDL¶
A literal DDL statement.
Specifies literal SQL DDL to be executed by the database. DDL objects function as DDL event listeners, and can be subscribed to those events listed in
DDLEvents
, using eitherTable
orMetaData
objects as targets. Basic templating support allows a single DDL instance to handle repetitive tasks for multiple tables.Examples:
from sqlalchemy import event, DDL tbl = Table('users', metadata, Column('uid', Integer)) event.listen(tbl, 'before_create', DDL('DROP TRIGGER users_trigger')) spow = DDL('ALTER TABLE %(table)s SET secretpowers TRUE') event.listen(tbl, 'after_create', spow.execute_if(dialect='somedb')) drop_spow = DDL('ALTER TABLE users SET secretpowers FALSE') connection.execute(drop_spow)
When operating on Table events, the following
statement
string substitutions are available:%(table)s - the Table name, with any required quoting applied %(schema)s - the schema name, with any required quoting applied %(fullname)s - the Table name including schema, quoted if needed
The DDL’s “context”, if any, will be combined with the standard substitutions noted above. Keys present in the context will override the standard substitutions.
Members
Class signature
class
sqlalchemy.schema.DDL
(sqlalchemy.schema.ExecutableDDLElement
)-
method
sqlalchemy.schema.DDL.
__init__(statement, context=None)¶ Create a DDL statement.
- Parameters:
statement¶ –
A string or unicode string to be executed. Statements will be processed with Python’s string formatting operator using a fixed set of string substitutions, as well as additional substitutions provided by the optional
DDL.context
parameter.A literal ‘%’ in a statement must be escaped as ‘%%’.
SQL bind parameters are not available in DDL statements.
context¶ – Optional dictionary, defaults to None. These values will be available for use in string substitutions on the DDL statement.
-
method
- class sqlalchemy.schema._CreateDropBase¶
Base class for DDL constructs that represent CREATE and DROP or equivalents.
The common theme of _CreateDropBase is a single
element
attribute which refers to the element to be created or dropped.Class signature
class
sqlalchemy.schema._CreateDropBase
(sqlalchemy.schema.ExecutableDDLElement
)
- class sqlalchemy.schema.CreateTable¶
Represent a CREATE TABLE statement.
Members
Class signature
class
sqlalchemy.schema.CreateTable
(sqlalchemy.schema._CreateBase
)-
method
sqlalchemy.schema.CreateTable.
__init__(element: Table, include_foreign_key_constraints: typing_Sequence[ForeignKeyConstraint] | None = None, if_not_exists: bool = False)¶ Create a
CreateTable
construct.- Parameters:
include_foreign_key_constraints¶ – optional sequence of
ForeignKeyConstraint
objects that will be included inline within the CREATE construct; if omitted, all foreign key constraints that do not specify use_alter=True are included.if_not_exists¶ –
if True, an IF NOT EXISTS operator will be applied to the construct.
New in version 1.4.0b2.
-
method
- class sqlalchemy.schema.DropTable¶
Represent a DROP TABLE statement.
Members
Class signature
class
sqlalchemy.schema.DropTable
(sqlalchemy.schema._DropBase
)-
method
sqlalchemy.schema.DropTable.
__init__(element: Table, if_exists: bool = False)¶ Create a
DropTable
construct.
-
method
- class sqlalchemy.schema.CreateColumn¶
Represent a
Column
as rendered in a CREATE TABLE statement, via theCreateTable
construct.This is provided to support custom column DDL within the generation of CREATE TABLE statements, by using the compiler extension documented in Custom SQL Constructs and Compilation Extension to extend
CreateColumn
.Typical integration is to examine the incoming
Column
object, and to redirect compilation if a particular flag or condition is found:from sqlalchemy import schema from sqlalchemy.ext.compiler import compiles @compiles(schema.CreateColumn) def compile(element, compiler, **kw): column = element.element if "special" not in column.info: return compiler.visit_create_column(element, **kw) text = "%s SPECIAL DIRECTIVE %s" % ( column.name, compiler.type_compiler.process(column.type) ) default = compiler.get_column_default_string(column) if default is not None: text += " DEFAULT " + default if not column.nullable: text += " NOT NULL" if column.constraints: text += " ".join( compiler.process(const) for const in column.constraints) return text
The above construct can be applied to a
Table
as follows:from sqlalchemy import Table, Metadata, Column, Integer, String from sqlalchemy import schema metadata = MetaData() table = Table('mytable', MetaData(), Column('x', Integer, info={"special":True}, primary_key=True), Column('y', String(50)), Column('z', String(20), info={"special":True}) ) metadata.create_all(conn)
Above, the directives we’ve added to the
Column.info
collection will be detected by our custom compilation scheme:CREATE TABLE mytable ( x SPECIAL DIRECTIVE INTEGER NOT NULL, y VARCHAR(50), z SPECIAL DIRECTIVE VARCHAR(20), PRIMARY KEY (x) )
The
CreateColumn
construct can also be used to skip certain columns when producing aCREATE TABLE
. This is accomplished by creating a compilation rule that conditionally returnsNone
. This is essentially how to produce the same effect as using thesystem=True
argument onColumn
, which marks a column as an implicitly-present “system” column.For example, suppose we wish to produce a
Table
which skips rendering of the PostgreSQLxmin
column against the PostgreSQL backend, but on other backends does render it, in anticipation of a triggered rule. A conditional compilation rule could skip this name only on PostgreSQL:from sqlalchemy.schema import CreateColumn @compiles(CreateColumn, "postgresql") def skip_xmin(element, compiler, **kw): if element.element.name == 'xmin': return None else: return compiler.visit_create_column(element, **kw) my_table = Table('mytable', metadata, Column('id', Integer, primary_key=True), Column('xmin', Integer) )
Above, a
CreateTable
construct will generate aCREATE TABLE
which only includes theid
column in the string; thexmin
column will be omitted, but only against the PostgreSQL backend.Class signature
class
sqlalchemy.schema.CreateColumn
(sqlalchemy.schema.BaseDDLElement
)
- class sqlalchemy.schema.CreateSequence¶
Represent a CREATE SEQUENCE statement.
Class signature
class
sqlalchemy.schema.CreateSequence
(sqlalchemy.schema._CreateBase
)
- class sqlalchemy.schema.DropSequence¶
Represent a DROP SEQUENCE statement.
Class signature
class
sqlalchemy.schema.DropSequence
(sqlalchemy.schema._DropBase
)
- class sqlalchemy.schema.CreateIndex¶
Represent a CREATE INDEX statement.
Members
Class signature
class
sqlalchemy.schema.CreateIndex
(sqlalchemy.schema._CreateBase
)-
method
sqlalchemy.schema.CreateIndex.
__init__(element, if_not_exists=False)¶ Create a
Createindex
construct.
-
method
- class sqlalchemy.schema.DropIndex¶
Represent a DROP INDEX statement.
Members
Class signature
class
sqlalchemy.schema.DropIndex
(sqlalchemy.schema._DropBase
)
- class sqlalchemy.schema.AddConstraint¶
Represent an ALTER TABLE ADD CONSTRAINT statement.
Class signature
class
sqlalchemy.schema.AddConstraint
(sqlalchemy.schema._CreateBase
)
- class sqlalchemy.schema.DropConstraint¶
Represent an ALTER TABLE DROP CONSTRAINT statement.
Class signature
class
sqlalchemy.schema.DropConstraint
(sqlalchemy.schema._DropBase
)
- class sqlalchemy.schema.CreateSchema¶
Represent a CREATE SCHEMA statement.
The argument here is the string name of the schema.
Members
Class signature
class
sqlalchemy.schema.CreateSchema
(sqlalchemy.schema._CreateBase
)-
method
sqlalchemy.schema.CreateSchema.
__init__(name, if_not_exists=False)¶ Create a new
CreateSchema
construct.
-
method
- class sqlalchemy.schema.DropSchema¶
Represent a DROP SCHEMA statement.
The argument here is the string name of the schema.
Members
Class signature
class
sqlalchemy.schema.DropSchema
(sqlalchemy.schema._DropBase
)-
method
sqlalchemy.schema.DropSchema.
__init__(name, cascade=False, if_exists=False)¶ Create a new
DropSchema
construct.
-
method