def describe_sqla_col(column: Column, sql_dialect: str = None) \
-> Dict[str, Any]:
"""
Describes a single SQLAlchemy :class:`Column` in the :ref:`NLPRP
<nlprp>` format, which follows ``INFORMATION_SCHEMA.COLUMNS`` closely.
Args:
column:
the :class:`Column`
sql_dialect:
preferred SQL dialect for response, or ``None`` for a default
"""
sql_dialect = sql_dialect or DEFAULT_NLPRP_SQL_DIALECT
assert sql_dialect in ALL_SQL_DIALECTS, (
f"Unknown SQL dialect {sql_dialect!r}; must be one of "
f"{ALL_SQL_DIALECTS}")
dialect = registry.load(sql_dialect)() # type: Dialect
# log.critical(f"dialect: {dialect}")
# dialect = MSDialect()
column_type = column.type.compile(dialect)
data_type = column_type.partition("(")[0]
# ... https://stackoverflow.com/questions/27387415/how-would-i-get-everything-before-a-in-a-string-python # noqa
return {
NlprpKeys.COLUMN_NAME: column.name,
NlprpKeys.COLUMN_TYPE: column_type,
NlprpKeys.DATA_TYPE: data_type,
NlprpKeys.IS_NULLABLE: column.nullable,
NlprpKeys.COLUMN_COMMENT: column.comment,
}
def get_dialect(self):
"""Return the SQLAlchemy database dialect class corresponding
to this URL's driver name.
"""
if "+" not in self.drivername:
name = self.drivername
else:
name = self.drivername.replace("+", ".")
from sqlalchemy.dialects import registry
cls = registry.load(name)
# check for legacy dialects that
# would return a module with 'dialect' as the
# actual class
if hasattr(cls, "dialect") and isinstance(cls.dialect, type) and issubclass(cls.dialect, Dialect):
return cls.dialect
else:
return cls
def get_dialect(self):
"""Return the SQLAlchemy database dialect class corresponding
to this URL's driver name.
"""
if '+' not in self.drivername:
name = self.drivername
else:
name = self.drivername.replace('+', '.')
from sqlalchemy.dialects import registry
cls = registry.load(name)
# check for legacy dialects that
# would return a module with 'dialect' as the
# actual class
if hasattr(cls, 'dialect') and \
isinstance(cls.dialect, type) and \
issubclass(cls.dialect, Dialect):
return cls.dialect
else:
return cls
def mock_sqlalchemy_engine(dialect):
"""
Create a sqlalchemy.engine.Engine without it connecting to a database.
Examples
--------
::
from siuba.sql import LazyTbl
from siuba import _, mutate, show_query
engine = mock_sqlalchemy_engine('postgresql')
tbl = LazyTbl(engine, 'some_table', ['x'])
query = mutate(tbl, y = _.x + _.x)
show_query(query)
"""
from sqlalchemy.engine import Engine
from sqlalchemy.dialects import registry
dialect_cls = registry.load('postgresql')
return Engine(None, dialect_cls(), '')
def test_dialect_registered(self):
from sqlalchemy.dialects import registry
assert registry.load(
'mssql.pyodbc_mssql') is dialect.MssqlDialect_pyodbc_quoted
def is_dialect_available(dialect: str) -> bool:
try:
sqlalchemy_registry.load(dialect)
return True
except (NoSuchModuleError, ImportError):
return False