heat.db.sqlalchemy.types module

heat.db.sqlalchemy.types module

class heat.db.sqlalchemy.types.Json(*args, **kwargs)[source]

Bases: heat.db.sqlalchemy.types.LongText

process_bind_param(value, dialect)[source]

Receive a bound parameter value to be converted.

Subclasses override this method to return the value that should be passed along to the underlying TypeEngine object, and from there to the DBAPI execute() method.

The operation could be anything desired to perform custom behavior, such as transforming or serializing data. This could also be used as a hook for validating logic.

This operation should be designed with the reverse operation in mind, which would be the process_result_value method of this class.

Parameters
  • value – Data to operate upon, of any type expected by this method in the subclass. Can be None.

  • dialect – the Dialect in use.

process_result_value(value, dialect)[source]

Receive a result-row column value to be converted.

Subclasses should implement this method to operate on data fetched from the database.

Subclasses override this method to return the value that should be passed back to the application, given a value that is already processed by the underlying TypeEngine object, originally from the DBAPI cursor method fetchone() or similar.

The operation could be anything desired to perform custom behavior, such as transforming or serializing data. This could also be used as a hook for validating logic.

Parameters
  • value – Data to operate upon, of any type expected by this method in the subclass. Can be None.

  • dialect – the Dialect in use.

This operation should be designed to be reversible by the “process_bind_param” method of this class.

class heat.db.sqlalchemy.types.List(*args, **kwargs)[source]

Bases: sqlalchemy.sql.type_api.TypeDecorator

cache_ok = True

Indicate if statements using this TypeDecorator are “safe to cache”.

The default value None will emit a warning and then not allow caching of a statement which includes this type. Set to False to disable statements using this type from being cached at all without a warning. When set to True, the object’s class and selected elements from its state will be used as part of the cache key, e.g.:

class MyType(TypeDecorator):
    impl = String

    cache_ok = True

    def __init__(self, choices):
        self.choices = tuple(choices)
        self.internal_only = True

The cache key for the above type would be equivalent to:

(<class '__main__.MyType'>, ('choices', ('a', 'b', 'c')))

The caching scheme will extract attributes from the type that correspond to the names of parameters in the __init__() method. Above, the “choices” attribute becomes part of the cache key but “internal_only” does not, because there is no parameter named “internal_only”.

The requirements for cacheable elements is that they are hashable and also that they indicate the same SQL rendered for expressions using this type every time for a given cache value.

New in version 1.4.14: - added the cache_ok flag to allow some configurability of caching for TypeDecorator classes.

impl

alias of sqlalchemy.sql.sqltypes.Text

load_dialect_impl(dialect)[source]

Return a TypeEngine object corresponding to a dialect.

This is an end-user override hook that can be used to provide differing types depending on the given dialect. It is used by the TypeDecorator implementation of type_engine() to help determine what type should ultimately be returned for a given TypeDecorator.

By default returns self.impl.

process_bind_param(value, dialect)[source]

Receive a bound parameter value to be converted.

Subclasses override this method to return the value that should be passed along to the underlying TypeEngine object, and from there to the DBAPI execute() method.

The operation could be anything desired to perform custom behavior, such as transforming or serializing data. This could also be used as a hook for validating logic.

This operation should be designed with the reverse operation in mind, which would be the process_result_value method of this class.

Parameters
  • value – Data to operate upon, of any type expected by this method in the subclass. Can be None.

  • dialect – the Dialect in use.

process_result_value(value, dialect)[source]

Receive a result-row column value to be converted.

Subclasses should implement this method to operate on data fetched from the database.

Subclasses override this method to return the value that should be passed back to the application, given a value that is already processed by the underlying TypeEngine object, originally from the DBAPI cursor method fetchone() or similar.

The operation could be anything desired to perform custom behavior, such as transforming or serializing data. This could also be used as a hook for validating logic.

Parameters
  • value – Data to operate upon, of any type expected by this method in the subclass. Can be None.

  • dialect – the Dialect in use.

This operation should be designed to be reversible by the “process_bind_param” method of this class.

class heat.db.sqlalchemy.types.LongText(*args, **kwargs)[source]

Bases: sqlalchemy.sql.type_api.TypeDecorator

cache_ok = True

Indicate if statements using this TypeDecorator are “safe to cache”.

The default value None will emit a warning and then not allow caching of a statement which includes this type. Set to False to disable statements using this type from being cached at all without a warning. When set to True, the object’s class and selected elements from its state will be used as part of the cache key, e.g.:

class MyType(TypeDecorator):
    impl = String

    cache_ok = True

    def __init__(self, choices):
        self.choices = tuple(choices)
        self.internal_only = True

The cache key for the above type would be equivalent to:

(<class '__main__.MyType'>, ('choices', ('a', 'b', 'c')))

The caching scheme will extract attributes from the type that correspond to the names of parameters in the __init__() method. Above, the “choices” attribute becomes part of the cache key but “internal_only” does not, because there is no parameter named “internal_only”.

The requirements for cacheable elements is that they are hashable and also that they indicate the same SQL rendered for expressions using this type every time for a given cache value.

New in version 1.4.14: - added the cache_ok flag to allow some configurability of caching for TypeDecorator classes.

impl

alias of sqlalchemy.sql.sqltypes.Text

load_dialect_impl(dialect)[source]

Return a TypeEngine object corresponding to a dialect.

This is an end-user override hook that can be used to provide differing types depending on the given dialect. It is used by the TypeDecorator implementation of type_engine() to help determine what type should ultimately be returned for a given TypeDecorator.

By default returns self.impl.

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