Core Internals¶

Some key internal constructs are listed here.

class sqlalchemy.engine.interfaces.Compiled(dialect, statement, bind=None, schema_translate_map=None, compile_kwargs={})¶

Represent a compiled SQL or DDL expression.

The __str__ method of the Compiled object should produce the actual text of the statement. Compiled objects are specific to their underlying database dialect, and also may or may not be specific to the columns referenced within a particular set of bind parameters. In no case should the Compiled object be dependent on the actual values of those bind parameters, even though it may reference those values as defaults.

__init__(dialect, statement, bind=None, schema_translate_map=None, compile_kwargs={})¶

Construct a new Compiled object.

Parameters:

dialect¶ – Dialect to compile against.
statement¶ – ClauseElement to be compiled.
bind¶ – Optional Engine or Connection to compile this statement against.
schema_translate_map¶ –
dictionary of schema names to be translated when forming the resultant SQL

New in version 1.1.

See also

Translation of Schema Names
compile_kwargs¶ – additional kwargs that will be passed to the initial call to Compiled.process().

compile()¶: Produce the internal string representation of this element.

Deprecated since version 0.7: The Compiled.compile() method is deprecated and will be removed in a future release. The Compiled object now runs its compilation within the constructor, and this method does nothing.

construct_params(params=None)¶

Return the bind params for this compiled object.

Parameters:	params¶ – a dict of string/object pairs whose values will override bind values compiled in to the statement.

execute(*multiparams, **params)¶: Execute this compiled object.

execution_options = {}¶: Execution options propagated from the statement. In some cases, sub-elements of the statement can modify these.

params¶: Return the bind params for this compiled object.

scalar(*multiparams, **params)¶: Execute this compiled object and return the result’s scalar value.

sql_compiler¶

Return a Compiled that is capable of processing SQL expressions.

If this compiler is one, it would likely just return ‘self’.

class sqlalchemy.sql.compiler.DDLCompiler(dialect, statement, bind=None, schema_translate_map=None, compile_kwargs={})¶

Bases: sqlalchemy.sql.compiler.Compiled

__eq__¶: inherited from the __eq__ attribute of object

Return self==value.

__init__(dialect, statement, bind=None, schema_translate_map=None, compile_kwargs={})¶

inherited from the __init__() method of Compiled

Construct a new Compiled object.

Parameters:

dialect¶ – Dialect to compile against.
statement¶ – ClauseElement to be compiled.
bind¶ – Optional Engine or Connection to compile this statement against.
schema_translate_map¶ –
dictionary of schema names to be translated when forming the resultant SQL

New in version 1.1.

See also

Translation of Schema Names
compile_kwargs¶ – additional kwargs that will be passed to the initial call to Compiled.process().

__le__¶: inherited from the __le__ attribute of object

Return self<=value.

__lt__¶: inherited from the __lt__ attribute of object

Return self<value.

__ne__¶: inherited from the __ne__ attribute of object

Return self!=value.

compile()¶: inherited from the compile() method of Compiled

Produce the internal string representation of this element.

Deprecated since version 0.7: The Compiled.compile() method is deprecated and will be removed in a future release. The Compiled object now runs its compilation within the constructor, and this method does nothing.

construct_params(params=None)¶

Return the bind params for this compiled object.

Parameters:	params¶ – a dict of string/object pairs whose values will override bind values compiled in to the statement.

define_constraint_remote_table(constraint, table, preparer)¶: Format the remote table clause of a CREATE CONSTRAINT clause.

execute(*multiparams, **params)¶: inherited from the execute() method of Compiled

Execute this compiled object.

params¶: inherited from the params attribute of Compiled

Return the bind params for this compiled object.

scalar(*multiparams, **params)¶: inherited from the scalar() method of Compiled

Execute this compiled object and return the result’s scalar value.

class sqlalchemy.engine.default.DefaultDialect(convert_unicode=False, encoding='utf-8', paramstyle=None, dbapi=None, implicit_returning=None, supports_right_nested_joins=None, case_sensitive=True, supports_native_boolean=None, empty_in_strategy='static', max_identifier_length=None, label_length=None, **kwargs)¶

Bases: sqlalchemy.engine.interfaces.Dialect

Default implementation of Dialect

__eq__¶: inherited from the __eq__ attribute of object

Return self==value.

__le__¶: inherited from the __le__ attribute of object

Return self<=value.

__lt__¶: inherited from the __lt__ attribute of object

Return self<value.

__ne__¶: inherited from the __ne__ attribute of object

Return self!=value.

connect(*cargs, **cparams)¶

return a callable which sets up a newly created DBAPI connection.

The callable accepts a single argument “conn” which is the DBAPI connection itself. It has no return value.

This is used to set dialect-wide per-connection options such as isolation modes, unicode modes, etc.

If a callable is returned, it will be assembled into a pool listener that receives the direct DBAPI connection, with all wrappers removed.

If None is returned, no listener will be generated.

construct_arguments = None¶

Optional set of argument specifiers for various SQLAlchemy constructs, typically schema items.

To implement, establish as a series of tuples, as in:

construct_arguments = [
    (schema.Index, {
        "using": False,
        "where": None,
        "ops": None
    })
]

If the above construct is established on the PostgreSQL dialect, the Index construct will now accept the keyword arguments postgresql_using, postgresql_where, nad postgresql_ops. Any other argument specified to the constructor of Index which is prefixed with postgresql_ will raise ArgumentError.

A dialect which does not include a construct_arguments member will not participate in the argument validation system. For such a dialect, any argument name is accepted by all participating constructs, within the namespace of arguments prefixed with that dialect name. The rationale here is so that third-party dialects that haven’t yet implemented this feature continue to function in the old way.

New in version 0.9.2.

See also

DialectKWArgs - implementing base class which consumes DefaultDialect.construct_arguments

create_connect_args(url)¶

Build DB-API compatible connection arguments.

Given a URL object, returns a tuple consisting of a *args/**kwargs suitable to send directly to the dbapi’s connect function.

create_xid()¶

Create a random two-phase transaction ID.

This id will be passed to do_begin_twophase(), do_rollback_twophase(), do_commit_twophase(). Its format is unspecified.

dbapi_exception_translation_map = {}¶: mapping used in the extremely unusual case that a DBAPI’s published exceptions don’t actually have the __name__ that they are linked towards.

New in version 1.0.5.

ddl_compiler¶: alias of sqlalchemy.sql.compiler.DDLCompiler

denormalize_name(name)¶

convert the given name to a case insensitive identifier for the backend if it is an all-lowercase name.

this method is only used if the dialect defines requires_name_normalize=True.

do_begin(dbapi_connection)¶

Provide an implementation of connection.begin(), given a DB-API connection.

The DBAPI has no dedicated “begin” method and it is expected that transactions are implicit. This hook is provided for those DBAPIs that might need additional help in this area.

Note that Dialect.do_begin() is not called unless a Transaction object is in use. The Dialect.do_autocommit() hook is provided for DBAPIs that need some extra commands emitted after a commit in order to enter the next transaction, when the SQLAlchemy Connection is used in its default “autocommit” mode.

Parameters:	dbapi_connection¶ – a DBAPI connection, typically proxied within a `ConnectionFairy`.

do_begin_twophase(connection, xid)¶

inherited from the do_begin_twophase() method of Dialect

Begin a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid

do_close(dbapi_connection)¶

Provide an implementation of connection.close(), given a DBAPI connection.

This hook is called by the Pool when a connection has been detached from the pool, or is being returned beyond the normal capacity of the pool.

do_commit(dbapi_connection)¶

Provide an implementation of connection.commit(), given a DB-API connection.

Parameters:	dbapi_connection¶ – a DBAPI connection, typically proxied within a `ConnectionFairy`.

do_commit_twophase(connection, xid, is_prepared=True, recover=False)¶

inherited from the do_commit_twophase() method of Dialect

Commit a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid is_prepared¶ – whether or not `TwoPhaseTransaction.prepare()` was called. recover¶ – if the recover flag was passed.

do_execute(cursor, statement, parameters, context=None)¶: Provide an implementation of cursor.execute(statement, parameters).

do_execute_no_params(cursor, statement, context=None)¶

Provide an implementation of cursor.execute(statement).

The parameter collection should not be sent.

do_executemany(cursor, statement, parameters, context=None)¶: Provide an implementation of cursor.executemany(statement, parameters).

do_prepare_twophase(connection, xid)¶

inherited from the do_prepare_twophase() method of Dialect

Prepare a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid

do_recover_twophase(connection)¶

inherited from the do_recover_twophase() method of Dialect

Recover list of uncommitted prepared two phase transaction identifiers on the given connection.

Parameters:	connection¶ – a `Connection`.

do_release_savepoint(connection, name)¶

Release the named savepoint on a connection.

Parameters:	connection¶ – a `Connection`. name¶ – savepoint name.

do_rollback(dbapi_connection)¶

Provide an implementation of connection.rollback(), given a DB-API connection.

Parameters:	dbapi_connection¶ – a DBAPI connection, typically proxied within a `ConnectionFairy`.

do_rollback_to_savepoint(connection, name)¶

Rollback a connection to the named savepoint.

Parameters:	connection¶ – a `Connection`. name¶ – savepoint name.

do_rollback_twophase(connection, xid, is_prepared=True, recover=False)¶

inherited from the do_rollback_twophase() method of Dialect

Rollback a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid is_prepared¶ – whether or not `TwoPhaseTransaction.prepare()` was called. recover¶ – if the recover flag was passed.

do_savepoint(connection, name)¶

Create a savepoint with the given name.

Parameters:	connection¶ – a `Connection`. name¶ – savepoint name.

classmethod engine_created(engine)¶

inherited from the engine_created() method of Dialect

A convenience hook called before returning the final Engine.

If the dialect returned a different class from the get_dialect_cls() method, then the hook is called on both classes, first on the dialect class returned by the get_dialect_cls() method and then on the class on which the method was called.

The hook should be used by dialects and/or wrappers to apply special events to the engine or its components. In particular, it allows a dialect-wrapping class to apply dialect-level events.

New in version 1.0.3.

execute_sequence_format¶: alias of builtins.tuple

execution_ctx_cls¶: alias of DefaultExecutionContext

get_check_constraints(connection, table_name, schema=None, **kw)¶

inherited from the get_check_constraints() method of Dialect

Return information about check constraints in table_name.

Given a string table_name and an optional string schema, return check constraint information as a list of dicts with these keys:

name: the check constraint’s name
sqltext: the check constraint’s SQL expression
**kw: other options passed to the dialect’s get_check_constraints() method.

New in version 1.1.0.

get_columns(connection, table_name, schema=None, **kw)¶

inherited from the get_columns() method of Dialect

Return information about columns in table_name.

Given a Connection, a string table_name, and an optional string schema, return column information as a list of dictionaries with these keys:

name

the column’s name

type

[sqlalchemy.types#TypeEngine]

nullable

boolean

default

the column’s default value

autoincrement

boolean

sequence

a dictionary of the form

{‘name’ : str, ‘start’ :int, ‘increment’: int, ‘minvalue’: int,: ‘maxvalue’: int, ‘nominvalue’: bool, ‘nomaxvalue’: bool, ‘cycle’: bool, ‘cache’: int, ‘order’: bool}

Additional column attributes may be present.

classmethod get_dialect_cls(url)¶

inherited from the get_dialect_cls() method of Dialect

Given a URL, return the Dialect that will be used.

This is a hook that allows an external plugin to provide functionality around an existing dialect, by allowing the plugin to be loaded from the url based on an entrypoint, and then the plugin returns the actual dialect to be used.

By default this just returns the cls.

New in version 1.0.3.

get_foreign_keys(connection, table_name, schema=None, **kw)¶

inherited from the get_foreign_keys() method of Dialect

Return information about foreign_keys in table_name.

Given a Connection, a string table_name, and an optional string schema, return foreign key information as a list of dicts with these keys:

name: the constraint’s name
constrained_columns: a list of column names that make up the foreign key
referred_schema: the name of the referred schema
referred_table: the name of the referred table
referred_columns: a list of column names in the referred table that correspond to constrained_columns

get_indexes(connection, table_name, schema=None, **kw)¶

inherited from the get_indexes() method of Dialect

Return information about indexes in table_name.

Given a Connection, a string table_name and an optional string schema, return index information as a list of dictionaries with these keys:

name: the index’s name
column_names: list of column names in order
unique: boolean

get_isolation_level(dbapi_conn)¶

inherited from the get_isolation_level() method of Dialect

Given a DBAPI connection, return its isolation level.

When working with a Connection object, the corresponding DBAPI connection may be procured using the Connection.connection accessor.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

get_pk_constraint(conn, table_name, schema=None, **kw)¶: Compatibility method, adapts the result of get_primary_keys() for those dialects which don’t implement get_pk_constraint().

get_primary_keys(connection, table_name, schema=None, **kw)¶: inherited from the get_primary_keys() method of Dialect

Return information about primary keys in table_name.

Deprecated since version 0.8: The Dialect.get_primary_keys() method is deprecated and will be removed in a future release. Please refer to the Dialect.get_pk_constraint() method.

get_table_comment(connection, table_name, schema=None, **kw)¶

inherited from the get_table_comment() method of Dialect

Return the “comment” for the table identified by table_name.

Given a string table_name and an optional string schema, return table comment information as a dictionary with this key:

text: text of the comment

Raises NotImplementedError for dialects that don’t support comments.

New in version 1.2.

get_table_names(connection, schema=None, **kw)¶: inherited from the get_table_names() method of Dialect

Return a list of table names for schema.

get_temp_table_names(connection, schema=None, **kw)¶: inherited from the get_temp_table_names() method of Dialect

Return a list of temporary table names on the given connection, if supported by the underlying backend.

get_temp_view_names(connection, schema=None, **kw)¶: inherited from the get_temp_view_names() method of Dialect

Return a list of temporary view names on the given connection, if supported by the underlying backend.

get_unique_constraints(connection, table_name, schema=None, **kw)¶

inherited from the get_unique_constraints() method of Dialect

Return information about unique constraints in table_name.

Given a string table_name and an optional string schema, return unique constraint information as a list of dicts with these keys:

name: the unique constraint’s name
column_names: list of column names in order
**kw: other options passed to the dialect’s get_unique_constraints() method.

New in version 0.9.0.

get_view_definition(connection, view_name, schema=None, **kw)¶

inherited from the get_view_definition() method of Dialect

Return view definition.

Given a Connection, a string view_name, and an optional string schema, return the view definition.

get_view_names(connection, schema=None, **kw)¶

inherited from the get_view_names() method of Dialect

Return a list of all view names available in the database.

schema:: Optional, retrieve names from a non-default schema.

has_sequence(connection, sequence_name, schema=None)¶

inherited from the has_sequence() method of Dialect

Check the existence of a particular sequence in the database.

Given a Connection object and a string sequence_name, return True if the given sequence exists in the database, False otherwise.

has_table(connection, table_name, schema=None)¶

inherited from the has_table() method of Dialect

Check the existence of a particular table in the database.

Given a Connection object and a string table_name, return True if the given table (possibly within the specified schema) exists in the database, False otherwise.

initialize(connection)¶

Called during strategized creation of the dialect with a connection.

Allows dialects to configure options based on server version info or other properties.

The connection passed here is a SQLAlchemy Connection object, with full capabilities.

The initialize() method of the base dialect should be called via super().

is_disconnect(e, connection, cursor)¶: Return True if the given DB-API error indicates an invalid connection

normalize_name(name)¶

convert the given name to lowercase if it is detected as case insensitive.

this method is only used if the dialect defines requires_name_normalize=True.

on_connect()¶

return a callable which sets up a newly created DBAPI connection.

This is used to set dialect-wide per-connection options such as isolation modes, unicode modes, etc.

If a callable is returned, it will be assembled into a pool listener that receives the direct DBAPI connection, with all wrappers removed.

If None is returned, no listener will be generated.

preparer¶: alias of sqlalchemy.sql.compiler.IdentifierPreparer

reflecttable(connection, table, include_columns, exclude_columns, resolve_fks, **opts)¶

Load table description from the database.

Given a Connection and a Table object, reflect its columns and properties from the database.

The implementation of this method is provided by DefaultDialect.reflecttable(), which makes use of Inspector to retrieve column information.

Dialects should not seek to implement this method, and should instead implement individual schema inspection operations such as Dialect.get_columns(), Dialect.get_pk_constraint(), etc.

reset_isolation_level(dbapi_conn)¶

Given a DBAPI connection, revert its isolation to the default.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

set_isolation_level(dbapi_conn, level)¶

inherited from the set_isolation_level() method of Dialect

Given a DBAPI connection, set its isolation level.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

statement_compiler¶: alias of sqlalchemy.sql.compiler.SQLCompiler

type_compiler¶: alias of sqlalchemy.sql.compiler.GenericTypeCompiler

type_descriptor(typeobj)¶

Provide a database-specific TypeEngine object, given the generic object which comes from the types module.

This method looks for a dictionary called colspecs as a class or instance-level variable, and passes on to types.adapt_type().

class sqlalchemy.engine.interfaces.Dialect¶

Define the behavior of a specific database and DB-API combination.

Any aspect of metadata definition, SQL query generation, execution, result-set handling, or anything else which varies between databases is defined under the general category of the Dialect. The Dialect acts as a factory for other database-specific object implementations including ExecutionContext, Compiled, DefaultGenerator, and TypeEngine.

All Dialects implement the following attributes:

name: identifying name for the dialect from a DBAPI-neutral point of view (i.e. ‘sqlite’)
driver: identifying name for the dialect’s DBAPI
positional: True if the paramstyle for this Dialect is positional.
paramstyle: the paramstyle to be used (some DB-APIs support multiple paramstyles).
convert_unicode: True if Unicode conversion should be applied to all str types.
encoding: type of encoding to use for unicode, usually defaults to ‘utf-8’.
statement_compiler: a Compiled class used to compile SQL statements
ddl_compiler: a Compiled class used to compile DDL statements
server_version_info: a tuple containing a version number for the DB backend in use. This value is only available for supporting dialects, and is typically populated during the initial connection to the database.
default_schema_name: the name of the default schema. This value is only available for supporting dialects, and is typically populated during the initial connection to the database.
execution_ctx_cls: a ExecutionContext class used to handle statement execution
execute_sequence_format: either the ‘tuple’ or ‘list’ type, depending on what cursor.execute() accepts for the second argument (they vary).
preparer: a IdentifierPreparer class used to quote identifiers.
supports_alter: True if the database supports ALTER TABLE.
max_identifier_length: The maximum length of identifier names.
supports_unicode_statements: Indicate whether the DB-API can receive SQL statements as Python unicode strings
supports_unicode_binds: Indicate whether the DB-API can receive string bind parameters as Python unicode strings
supports_sane_rowcount: Indicate whether the dialect properly implements rowcount for UPDATE and DELETE statements.
supports_sane_multi_rowcount: Indicate whether the dialect properly implements rowcount for UPDATE and DELETE statements when executed via executemany.
preexecute_autoincrement_sequences: True if ‘implicit’ primary key functions must be executed separately in order to get their value. This is currently oriented towards PostgreSQL.
implicit_returning: use RETURNING or equivalent during INSERT execution in order to load newly generated primary keys and other column defaults in one execution, which are then available via inserted_primary_key. If an insert statement has returning() specified explicitly, the “implicit” functionality is not used and inserted_primary_key will not be available.
colspecs: A dictionary of TypeEngine classes from sqlalchemy.types mapped to subclasses that are specific to the dialect class. This dictionary is class-level only and is not accessed from the dialect instance itself.
supports_default_values: Indicates if the construct INSERT INTO tablename DEFAULT VALUES is supported
supports_sequences: Indicates if the dialect supports CREATE SEQUENCE or similar.
sequences_optional: If True, indicates if the “optional” flag on the Sequence() construct should signal to not generate a CREATE SEQUENCE. Applies only to dialects that support sequences. Currently used only to allow PostgreSQL SERIAL to be used on a column that specifies Sequence() for usage on other backends.
supports_native_enum: Indicates if the dialect supports a native ENUM construct. This will prevent types.Enum from generating a CHECK constraint when that type is used.
supports_native_boolean: Indicates if the dialect supports a native boolean construct. This will prevent types.Boolean from generating a CHECK constraint when that type is used.
dbapi_exception_translation_map: A dictionary of names that will contain as values the names of pep-249 exceptions (“IntegrityError”, “OperationalError”, etc) keyed to alternate class names, to support the case where a DBAPI has exception classes that aren’t named as they are referred to (e.g. IntegrityError = MyException). In the vast majority of cases this dictionary is empty.

New in version 1.0.5.

connect()¶

return a callable which sets up a newly created DBAPI connection.

The callable accepts a single argument “conn” which is the DBAPI connection itself. It has no return value.

This is used to set dialect-wide per-connection options such as isolation modes, unicode modes, etc.

If a callable is returned, it will be assembled into a pool listener that receives the direct DBAPI connection, with all wrappers removed.

If None is returned, no listener will be generated.

create_connect_args(url)¶

Build DB-API compatible connection arguments.

Given a URL object, returns a tuple consisting of a *args/**kwargs suitable to send directly to the dbapi’s connect function.

create_xid()¶

Create a two-phase transaction ID.

This id will be passed to do_begin_twophase(), do_rollback_twophase(), do_commit_twophase(). Its format is unspecified.

denormalize_name(name)¶

convert the given name to a case insensitive identifier for the backend if it is an all-lowercase name.

this method is only used if the dialect defines requires_name_normalize=True.

do_begin(dbapi_connection)¶

Provide an implementation of connection.begin(), given a DB-API connection.

The DBAPI has no dedicated “begin” method and it is expected that transactions are implicit. This hook is provided for those DBAPIs that might need additional help in this area.

Note that Dialect.do_begin() is not called unless a Transaction object is in use. The Dialect.do_autocommit() hook is provided for DBAPIs that need some extra commands emitted after a commit in order to enter the next transaction, when the SQLAlchemy Connection is used in its default “autocommit” mode.

Parameters:	dbapi_connection¶ – a DBAPI connection, typically proxied within a `ConnectionFairy`.

do_begin_twophase(connection, xid)¶

Begin a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid

do_close(dbapi_connection)¶

Provide an implementation of connection.close(), given a DBAPI connection.

This hook is called by the Pool when a connection has been detached from the pool, or is being returned beyond the normal capacity of the pool.

do_commit(dbapi_connection)¶

Provide an implementation of connection.commit(), given a DB-API connection.

Parameters:	dbapi_connection¶ – a DBAPI connection, typically proxied within a `ConnectionFairy`.

do_commit_twophase(connection, xid, is_prepared=True, recover=False)¶

Commit a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid is_prepared¶ – whether or not `TwoPhaseTransaction.prepare()` was called. recover¶ – if the recover flag was passed.

do_execute(cursor, statement, parameters, context=None)¶: Provide an implementation of cursor.execute(statement, parameters).

do_execute_no_params(cursor, statement, parameters, context=None)¶

Provide an implementation of cursor.execute(statement).

The parameter collection should not be sent.

do_executemany(cursor, statement, parameters, context=None)¶: Provide an implementation of cursor.executemany(statement, parameters).

do_prepare_twophase(connection, xid)¶

Prepare a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid

do_recover_twophase(connection)¶

Recover list of uncommitted prepared two phase transaction identifiers on the given connection.

Parameters:	connection¶ – a `Connection`.

do_release_savepoint(connection, name)¶

Release the named savepoint on a connection.

Parameters:	connection¶ – a `Connection`. name¶ – savepoint name.

do_rollback(dbapi_connection)¶

Provide an implementation of connection.rollback(), given a DB-API connection.

Parameters:	dbapi_connection¶ – a DBAPI connection, typically proxied within a `ConnectionFairy`.

do_rollback_to_savepoint(connection, name)¶

Rollback a connection to the named savepoint.

Parameters:	connection¶ – a `Connection`. name¶ – savepoint name.

do_rollback_twophase(connection, xid, is_prepared=True, recover=False)¶

Rollback a two phase transaction on the given connection.

Parameters:	connection¶ – a `Connection`. xid¶ – xid is_prepared¶ – whether or not `TwoPhaseTransaction.prepare()` was called. recover¶ – if the recover flag was passed.

do_savepoint(connection, name)¶

Create a savepoint with the given name.

Parameters:	connection¶ – a `Connection`. name¶ – savepoint name.

classmethod engine_created(engine)¶

A convenience hook called before returning the final Engine.

If the dialect returned a different class from the get_dialect_cls() method, then the hook is called on both classes, first on the dialect class returned by the get_dialect_cls() method and then on the class on which the method was called.

The hook should be used by dialects and/or wrappers to apply special events to the engine or its components. In particular, it allows a dialect-wrapping class to apply dialect-level events.

New in version 1.0.3.

get_check_constraints(connection, table_name, schema=None, **kw)¶

Return information about check constraints in table_name.

Given a string table_name and an optional string schema, return check constraint information as a list of dicts with these keys:

name: the check constraint’s name
sqltext: the check constraint’s SQL expression
**kw: other options passed to the dialect’s get_check_constraints() method.

New in version 1.1.0.

get_columns(connection, table_name, schema=None, **kw)¶

Return information about columns in table_name.

Given a Connection, a string table_name, and an optional string schema, return column information as a list of dictionaries with these keys:

name

the column’s name

type

[sqlalchemy.types#TypeEngine]

nullable

boolean

default

the column’s default value

autoincrement

boolean

sequence

a dictionary of the form

{‘name’ : str, ‘start’ :int, ‘increment’: int, ‘minvalue’: int,: ‘maxvalue’: int, ‘nominvalue’: bool, ‘nomaxvalue’: bool, ‘cycle’: bool, ‘cache’: int, ‘order’: bool}

Additional column attributes may be present.

classmethod get_dialect_cls(url)¶

Given a URL, return the Dialect that will be used.

This is a hook that allows an external plugin to provide functionality around an existing dialect, by allowing the plugin to be loaded from the url based on an entrypoint, and then the plugin returns the actual dialect to be used.

By default this just returns the cls.

New in version 1.0.3.

get_foreign_keys(connection, table_name, schema=None, **kw)¶

Return information about foreign_keys in table_name.

Given a Connection, a string table_name, and an optional string schema, return foreign key information as a list of dicts with these keys:

name: the constraint’s name
constrained_columns: a list of column names that make up the foreign key
referred_schema: the name of the referred schema
referred_table: the name of the referred table
referred_columns: a list of column names in the referred table that correspond to constrained_columns

get_indexes(connection, table_name, schema=None, **kw)¶

Return information about indexes in table_name.

Given a Connection, a string table_name and an optional string schema, return index information as a list of dictionaries with these keys:

name: the index’s name
column_names: list of column names in order
unique: boolean

get_isolation_level(dbapi_conn)¶

Given a DBAPI connection, return its isolation level.

When working with a Connection object, the corresponding DBAPI connection may be procured using the Connection.connection accessor.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

get_pk_constraint(connection, table_name, schema=None, **kw)¶

Return information about the primary key constraint on table_name`.

Given a Connection, a string table_name, and an optional string schema, return primary key information as a dictionary with these keys:

constrained_columns: a list of column names that make up the primary key
name: optional name of the primary key constraint.

get_primary_keys(connection, table_name, schema=None, **kw)¶: Return information about primary keys in table_name.

Deprecated since version 0.8: The Dialect.get_primary_keys() method is deprecated and will be removed in a future release. Please refer to the Dialect.get_pk_constraint() method.

get_table_comment(connection, table_name, schema=None, **kw)¶

Return the “comment” for the table identified by table_name.

Given a string table_name and an optional string schema, return table comment information as a dictionary with this key:

text: text of the comment

Raises NotImplementedError for dialects that don’t support comments.

New in version 1.2.

get_table_names(connection, schema=None, **kw)¶: Return a list of table names for schema.

get_temp_table_names(connection, schema=None, **kw)¶: Return a list of temporary table names on the given connection, if supported by the underlying backend.

get_temp_view_names(connection, schema=None, **kw)¶: Return a list of temporary view names on the given connection, if supported by the underlying backend.

get_unique_constraints(connection, table_name, schema=None, **kw)¶

Return information about unique constraints in table_name.

Given a string table_name and an optional string schema, return unique constraint information as a list of dicts with these keys:

name: the unique constraint’s name
column_names: list of column names in order
**kw: other options passed to the dialect’s get_unique_constraints() method.

New in version 0.9.0.

get_view_definition(connection, view_name, schema=None, **kw)¶

Return view definition.

Given a Connection, a string view_name, and an optional string schema, return the view definition.

get_view_names(connection, schema=None, **kw)¶

Return a list of all view names available in the database.

schema:: Optional, retrieve names from a non-default schema.

has_sequence(connection, sequence_name, schema=None)¶

Check the existence of a particular sequence in the database.

Given a Connection object and a string sequence_name, return True if the given sequence exists in the database, False otherwise.

has_table(connection, table_name, schema=None)¶

Check the existence of a particular table in the database.

Given a Connection object and a string table_name, return True if the given table (possibly within the specified schema) exists in the database, False otherwise.

initialize(connection)¶

Called during strategized creation of the dialect with a connection.

Allows dialects to configure options based on server version info or other properties.

The connection passed here is a SQLAlchemy Connection object, with full capabilities.

The initialize() method of the base dialect should be called via super().

is_disconnect(e, connection, cursor)¶: Return True if the given DB-API error indicates an invalid connection

normalize_name(name)¶

convert the given name to lowercase if it is detected as case insensitive.

this method is only used if the dialect defines requires_name_normalize=True.

reflecttable(connection, table, include_columns, exclude_columns, resolve_fks)¶

Load table description from the database.

Given a Connection and a Table object, reflect its columns and properties from the database.

The implementation of this method is provided by DefaultDialect.reflecttable(), which makes use of Inspector to retrieve column information.

Dialects should not seek to implement this method, and should instead implement individual schema inspection operations such as Dialect.get_columns(), Dialect.get_pk_constraint(), etc.

reset_isolation_level(dbapi_conn)¶

Given a DBAPI connection, revert its isolation to the default.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

set_isolation_level(dbapi_conn, level)¶

Given a DBAPI connection, set its isolation level.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

classmethod type_descriptor(typeobj)¶

Transform a generic type to a dialect-specific type.

Dialect classes will usually use the types.adapt_type() function in the types module to accomplish this.

The returned result is cached per dialect class so can contain no dialect-instance state.

class sqlalchemy.engine.default.DefaultExecutionContext¶

Bases: sqlalchemy.engine.interfaces.ExecutionContext

create_cursor()¶

Return a new cursor generated from this ExecutionContext’s connection.

Some dialects may wish to change the behavior of connection.cursor(), such as postgresql which may return a PG “server side” cursor.

current_parameters = None¶

A dictionary of parameters applied to the current row.

This attribute is only available in the context of a user-defined default generation function, e.g. as described at Context-Sensitive Default Functions. It consists of a dictionary which includes entries for each column/value pair that is to be part of the INSERT or UPDATE statement. The keys of the dictionary will be the key value of each Column, which is usually synonymous with the name.

Note that the DefaultExecutionContext.current_parameters attribute does not accommodate for the “multi-values” feature of the Insert.values() method. The DefaultExecutionContext.get_current_parameters() method should be preferred.

Context-Sensitive Default Functions

get_current_parameters(isolate_multiinsert_groups=True)¶

Return a dictionary of parameters applied to the current row.

This method can only be used in the context of a user-defined default generation function, e.g. as described at Context-Sensitive Default Functions. When invoked, a dictionary is returned which includes entries for each column/value pair that is part of the INSERT or UPDATE statement. The keys of the dictionary will be the key value of each Column, which is usually synonymous with the name.

Parameters:	isolate_multiinsert_groups=True¶ – indicates that multi-valued INSERT constructs created using `Insert.values()` should be handled by returning only the subset of parameters that are local to the current column default invocation. When `False`, the raw parameters of the statement are returned including the naming convention used in the case of multi-valued INSERT.

New in version 1.2: added DefaultExecutionContext.get_current_parameters() which provides more functionality over the existing DefaultExecutionContext.current_parameters attribute.

Context-Sensitive Default Functions

get_lastrowid()¶

return self.cursor.lastrowid, or equivalent, after an INSERT.

This may involve calling special cursor functions, issuing a new SELECT on the cursor (or a new one), or returning a stored value that was calculated within post_exec().

This function will only be called for dialects which support “implicit” primary key generation, keep preexecute_autoincrement_sequences set to False, and when no explicit id value was bound to the statement.

The function is called once, directly after post_exec() and before the transaction is committed or ResultProxy is generated. If the post_exec() method assigns a value to self._lastrowid, the value is used in place of calling get_lastrowid().

Note that this method is not equivalent to the lastrowid method on ResultProxy, which is a direct proxy to the DBAPI lastrowid accessor in all cases.

get_result_processor(type_, colname, coltype)¶

Return a ‘result processor’ for a given type as present in cursor.description.

This has a default implementation that dialects can override for context-sensitive result type handling.

handle_dbapi_exception(e)¶: Receive a DBAPI exception which occurred upon execute, result fetch, etc.

lastrow_has_defaults()¶: Return True if the last INSERT or UPDATE row contained inlined or database-side defaults.

post_exec()¶

Called after the execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the last_insert_ids, last_inserted_params, etc. datamembers should be available after this method completes.

pre_exec()¶

Called before an execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the statement and parameters datamembers must be initialized after this statement is complete.

set_input_sizes(translate=None, include_types=None, exclude_types=None)¶

Given a cursor and ClauseParameters, call the appropriate style of setinputsizes() on the cursor, using DB-API types from the bind parameter’s TypeEngine objects.

This method only called by those dialects which require it, currently cx_oracle.

should_autocommit_text(statement)¶: Parse the given textual statement and return True if it refers to a “committable” statement

class sqlalchemy.engine.interfaces.ExecutionContext¶

A messenger object for a Dialect that corresponds to a single execution.

ExecutionContext should have these data members:

connection: Connection object which can be freely used by default value generators to execute SQL. This Connection should reference the same underlying connection/transactional resources of root_connection.
root_connection: Connection object which is the source of this ExecutionContext. This Connection may have close_with_result=True set, in which case it can only be used once.
dialect: dialect which created this ExecutionContext.
cursor: DB-API cursor procured from the connection,
compiled: if passed to constructor, sqlalchemy.engine.base.Compiled object being executed,
statement: string version of the statement to be executed. Is either passed to the constructor, or must be created from the sql.Compiled object by the time pre_exec() has completed.
parameters: bind parameters passed to the execute() method. For compiled statements, this is a dictionary or list of dictionaries. For textual statements, it should be in a format suitable for the dialect’s paramstyle (i.e. dict or list of dicts for non positional, list or list of lists/tuples for positional).
isinsert: True if the statement is an INSERT.
isupdate: True if the statement is an UPDATE.
should_autocommit: True if the statement is a “committable” statement.
prefetch_cols: a list of Column objects for which a client-side default was fired off. Applies to inserts and updates.
postfetch_cols: a list of Column objects for which a server-side default or inline SQL expression value was fired off. Applies to inserts and updates.

create_cursor()¶

Return a new cursor generated from this ExecutionContext’s connection.

Some dialects may wish to change the behavior of connection.cursor(), such as postgresql which may return a PG “server side” cursor.

exception = None¶

A DBAPI-level exception that was caught when this ExecutionContext attempted to execute a statement.

This attribute is meaningful only within the ConnectionEvents.dbapi_error() event.

New in version 0.9.7.

See also

ExecutionContext.is_disconnect

ConnectionEvents.dbapi_error()

get_rowcount()¶

Return the DBAPI cursor.rowcount value, or in some cases an interpreted value.

See ResultProxy.rowcount for details on this.

handle_dbapi_exception(e)¶: Receive a DBAPI exception which occurred upon execute, result fetch, etc.

is_disconnect = None¶

Boolean flag set to True or False when a DBAPI-level exception is caught when this ExecutionContext attempted to execute a statement.

This attribute is meaningful only within the ConnectionEvents.dbapi_error() event.

New in version 0.9.7.

See also

ExecutionContext.exception

ConnectionEvents.dbapi_error()

lastrow_has_defaults()¶: Return True if the last INSERT or UPDATE row contained inlined or database-side defaults.

post_exec()¶

Called after the execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the last_insert_ids, last_inserted_params, etc. datamembers should be available after this method completes.

pre_exec()¶

Called before an execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the statement and parameters datamembers must be initialized after this statement is complete.

result()¶

Return a result object corresponding to this ExecutionContext.

Returns a ResultProxy.

should_autocommit_text(statement)¶: Parse the given textual statement and return True if it refers to a “committable” statement

class sqlalchemy.sql.compiler.GenericTypeCompiler(dialect)¶

Bases: sqlalchemy.sql.compiler.TypeCompiler

__eq__¶: inherited from the __eq__ attribute of object

Return self==value.

__le__¶: inherited from the __le__ attribute of object

Return self<=value.

__lt__¶: inherited from the __lt__ attribute of object

Return self<value.

__ne__¶: inherited from the __ne__ attribute of object

Return self!=value.

class sqlalchemy.log.Identified¶

class sqlalchemy.sql.compiler.IdentifierPreparer(dialect, initial_quote='"', final_quote=None, escape_quote='"', quote_case_sensitive_collations=True, omit_schema=False)¶

Handle quoting and case-folding of identifiers based on options.

__init__(dialect, initial_quote='"', final_quote=None, escape_quote='"', quote_case_sensitive_collations=True, omit_schema=False)¶

Construct a new IdentifierPreparer object.

initial_quote: Character that begins a delimited identifier.
final_quote: Character that ends a delimited identifier. Defaults to initial_quote.
omit_schema: Prevent prepending schema name. Useful for databases that do not support schemae.

format_column(column, use_table=False, name=None, table_name=None, use_schema=False)¶: Prepare a quoted column name.

format_schema(name)¶: Prepare a quoted schema name.

format_table(table, use_schema=True, name=None)¶: Prepare a quoted table and schema name.

format_table_seq(table, use_schema=True)¶: Format table name and schema as a tuple.

quote(ident, force=None)¶

Conditionally quote an identfier.

The identifier is quoted if it is a reserved word, contains quote-necessary characters, or is an instance of quoted_name which includes quote set to True.

Subclasses can override this to provide database-dependent quoting behavior for identifier names.

Parameters:	ident¶ – string identifier force¶ – unused Deprecated since version 0.9: The `IdentifierPreparer.quote.force` parameter is deprecated and will be removed in a future release. This flag has no effect on the behavior of the `IdentifierPreparer.quote()` method; please refer to `quoted_name`.

quote_identifier(value)¶

Quote an identifier.

Subclasses should override this to provide database-dependent quoting behavior.

quote_schema(schema, force=None)¶

Conditionally quote a schema name.

The name is quoted if it is a reserved word, contains quote-necessary characters, or is an instance of quoted_name which includes quote set to True.

Subclasses can override this to provide database-dependent quoting behavior for schema names.

Parameters:	schema¶ – string schema name force¶ – unused Deprecated since version 0.9: The `IdentifierPreparer.quote_schema.force` parameter is deprecated and will be removed in a future release. This flag has no effect on the behavior of the `IdentifierPreparer.quote()` method; please refer to `quoted_name`.

unformat_identifiers(identifiers)¶: Unpack ‘schema.table.column’-like strings into components.

validate_sql_phrase(element, reg)¶

keyword sequence filter.

a filter for elements that are intended to represent keyword sequences, such as “INITIALLY”, “INITIALLY DEFERRED”, etc. no special characters should be present.

New in version 1.3.

class sqlalchemy.sql.compiler.SQLCompiler(dialect, statement, column_keys=None, inline=False, **kwargs)¶

Bases: sqlalchemy.sql.compiler.Compiled

Default implementation of Compiled.

Compiles ClauseElement objects into SQL strings.

__init__(dialect, statement, column_keys=None, inline=False, **kwargs)¶

Construct a new SQLCompiler object.

Parameters:	dialect¶ – `Dialect` to be used statement¶ – `ClauseElement` to be compiled column_keys¶ – a list of column names to be compiled into an INSERT or UPDATE statement. inline¶ – whether to generate INSERT statements as “inline”, e.g. not formatted to return any generated defaults kwargs¶ – additional keyword arguments to be consumed by the superclass.

ansi_bind_rules = False¶: SQL 92 doesn’t allow bind parameters to be used in the columns clause of a SELECT, nor does it allow ambiguous expressions like “? = ?”. A compiler subclass can set this flag to False if the target driver/DB enforces this

construct_params(params=None, _group_number=None, _check=True)¶: return a dictionary of bind parameter keys and values

contains_expanding_parameters = False¶

True if we’ve encountered bindparam(…, expanding=True).

These need to be converted before execution time against the string statement.

default_from()¶

Called when a SELECT statement has no froms, and no FROM clause is to be appended.

Gives Oracle a chance to tack on a FROM DUAL to the string output.

delete_extra_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)¶

Provide a hook to override the generation of an DELETE..FROM clause.

This can be used to implement DELETE..USING for example.

MySQL and MSSQL override this.

get_select_precolumns(select, **kw)¶: Called when building a SELECT statement, position is just before column list.

group_by_clause(select, **kw)¶: allow dialects to customize how GROUP BY is rendered.

insert_single_values_expr = None¶: When an INSERT is compiled with a single set of parameters inside a VALUES expression, the string is assigned here, where it can be used for insert batching schemes to rewrite the VALUES expression.

New in version 1.3.8.

isdelete = False¶: class-level defaults which can be set at the instance level to define if this Compiled instance represents INSERT/UPDATE/DELETE

order_by_clause(select, **kw)¶: allow dialects to customize how ORDER BY is rendered.

params¶: Return the bind param dictionary embedded into this compiled object, for those values that are present.

render_literal_value(value, type_)¶

Render the value of a bind parameter as a quoted literal.

This is used for statement sections that do not accept bind parameters on the target driver/database.

This should be implemented by subclasses using the quoting services of the DBAPI.

render_table_with_column_in_update_from = False¶: set to True classwide to indicate the SET clause in a multi-table UPDATE statement should qualify columns with the table name (i.e. MySQL only)

returning = None¶: holds the “returning” collection of columns if the statement is CRUD and defines returning columns either implicitly or explicitly

returning_precedes_values = False¶: set to True classwide to generate RETURNING clauses before the VALUES or WHERE clause (i.e. MSSQL)

sql_compiler¶

Return a Compiled that is capable of processing SQL expressions.

If this compiler is one, it would likely just return ‘self’.

update_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)¶

Provide a hook to override the generation of an UPDATE..FROM clause.

MySQL and MSSQL override this.

update_limit_clause(update_stmt)¶: Provide a hook for MySQL to add LIMIT to the UPDATE

update_tables_clause(update_stmt, from_table, extra_froms, **kw)¶

Provide a hook to override the initial table clause in an UPDATE statement.

MySQL overrides this.

class sqlalchemy.sql.compiler.StrSQLCompiler(dialect, statement, column_keys=None, inline=False, **kwargs)¶

Bases: sqlalchemy.sql.compiler.SQLCompiler

A SQLCompiler subclass which allows a small selection of non-standard SQL features to render into a string value.

The StrSQLCompiler is invoked whenever a Core expression element is directly stringified without calling upon the ClauseElement.compile() method. It can render a limited set of non-standard SQL constructs to assist in basic stringification, however for more substantial custom or dialect-specific SQL constructs, it will be necessary to make use of ClauseElement.compile() directly.

delete_extra_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)¶

Provide a hook to override the generation of an DELETE..FROM clause.

This can be used to implement DELETE..USING for example.

MySQL and MSSQL override this.

update_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)¶

Provide a hook to override the generation of an UPDATE..FROM clause.

MySQL and MSSQL override this.

SQLAlchemy 1.3 Documentation

SQLAlchemy 1.3 Documentation

SQLAlchemy Core

Core Internals¶