Coverage for python / felis / db / database_context.py: 32%
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1"""API for managing database operations across different dialects."""
3# This file is part of felis.
4#
5# Developed for the LSST Data Management System.
6# This product includes software developed by the LSST Project
7# (https://www.lsst.org).
8# See the COPYRIGHT file at the top-level directory of this distribution
9# for details of code ownership.
10#
11# This program is free software: you can redistribute it and/or modify
12# it under the terms of the GNU General Public License as published by
13# the Free Software Foundation, either version 3 of the License, or
14# (at your option) any later version.
15#
16# This program is distributed in the hope that it will be useful,
17# but WITHOUT ANY WARRANTY; without even the implied warranty of
18# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19# GNU General Public License for more details.
20#
21# You should have received a copy of the GNU General Public License
22# along with this program. If not, see <https://www.gnu.org/licenses/>.
24from __future__ import annotations
26import logging
27from abc import abstractmethod
28from collections.abc import Callable, Iterator
29from contextlib import AbstractContextManager, contextmanager
30from typing import IO, Any, Literal, TypeAlias
32from sqlalchemy import (
33 Engine,
34 MetaData,
35 create_engine,
36 inspect,
37 make_url,
38 quoted_name,
39)
40from sqlalchemy.engine import (
41 Connection,
42 Dialect,
43 Result,
44)
45from sqlalchemy.engine.mock import MockConnection, create_mock_engine
46from sqlalchemy.engine.url import URL
47from sqlalchemy.exc import SQLAlchemyError
48from sqlalchemy.schema import (
49 CreateSchema,
50 DropSchema,
51)
52from sqlalchemy.sql import (
53 Executable,
54 text,
55)
56from sqlalchemy.sql.elements import TextClause
58__all__ = [
59 "DatabaseContext",
60 "DatabaseContextError",
61 "MockContext",
62 "MySQLContext",
63 "PostgreSQLContext",
64 "SQLiteContext",
65 "create_database_context",
66]
68logger = logging.getLogger("felis")
70SQLStatement = str | Executable | TextClause
73def _normalize_statement(statement: SQLStatement) -> Executable | TextClause:
74 if isinstance(statement, str):
75 return text(statement)
76 return statement
79def _create_mock_connection(engine_url: str | URL, output_file: IO[str] | None = None) -> MockConnection:
80 writer = _SQLWriter(output_file)
81 engine = create_mock_engine(engine_url, executor=writer.write, paramstyle="pyformat")
82 writer.dialect = engine.dialect
83 return engine
86def _dialect_name(url: URL) -> str:
87 dialect_name = url.drivername
88 # Normalize dialect name (e.g., "postgresql+psycopg2" -> "postgresql")
89 if "+" in dialect_name:
90 dialect_name = dialect_name.split("+")[0]
91 return dialect_name
94def _clear_schema(metadata: MetaData) -> None:
95 if metadata.schema:
96 metadata.schema = None
97 for table in metadata.tables.values():
98 table.schema = None
101def _get_existing_indexes(inspector: Any, table_name: str, schema: str | None) -> set[str]:
102 return {
103 ix["name"]
104 for ix in inspector.get_indexes(table_name, schema=schema)
105 if "name" in ix and ix["name"] is not None
106 }
109def is_mock_url(url: URL) -> bool:
110 """Check if the engine URL points to a mock connection.
112 Parameters
113 ----------
114 url
115 The SQLAlchemy engine URL.
117 Returns
118 -------
119 bool
120 True if the URL is a mock URL, False otherwise.
121 """
122 return (url.drivername == "sqlite" and url.database is None) or (
123 url.drivername != "sqlite" and url.host is None
124 )
127def is_sqlite_url(url: URL | str) -> bool:
128 """Check if the engine URL points to a SQLite database.
130 Parameters
131 ----------
132 url
133 The SQLAlchemy engine URL or string.
135 Returns
136 -------
137 bool
138 True if the URL is a SQLite URL, False otherwise.
139 """
140 if isinstance(url, str):
141 url = make_url(url)
142 return url.drivername.startswith("sqlite")
145class DatabaseContextError(Exception):
146 """Exception raised for errors in the DatabaseContext operations."""
149class DatabaseContext(AbstractContextManager):
150 """Interface for managing database operations across different
151 SQL dialects.
152 """
154 def __exit__(self, exc_type: Any, exc_val: Any, exc_tb: Any) -> Literal[False]:
155 """Exit the context manager and clean up resources."""
156 try:
157 self.close()
158 except Exception:
159 logger.exception("Error during cleanup of database context")
160 return False
162 @abstractmethod
163 def close(self) -> None:
164 """Close and clean up database resources."""
165 ...
167 @property
168 @abstractmethod
169 def metadata(self) -> MetaData:
170 """The SQLAlchemy metadata representing the database for the context
171 (`~sqlalchemy.sql.schema.MetaData`).
172 """
173 ...
175 @property
176 @abstractmethod
177 def engine(self) -> Engine:
178 """The SQAlchemy engine for the context
179 (`~sqlalchemy.engine.Engine`).
180 """
181 ...
183 @property
184 @abstractmethod
185 def dialect(self) -> Dialect:
186 """The SQLAlchemy dialect for the context
187 (`~sqlalchemy.engine.Dialect`).
188 """
189 ...
191 @property
192 @abstractmethod
193 def dialect_name(self) -> str:
194 """Get the dialect name for this database context (``str``)."""
195 ...
197 @abstractmethod
198 def initialize(self) -> None:
199 """Create the target schema in the database if it does not exist
200 already.
202 Sub-classes should implement idempotent behavior so that calling this
203 method multiple times has no adverse effects. If the schema already
204 exists, the method should simply return without raising an error. (A
205 warning message may be logged in this case.)
207 Raises
208 ------
209 DatabaseContextError
210 If there is an error instantiating the schema.
211 """
212 ...
214 @abstractmethod
215 def drop(self) -> None:
216 """Drop the schema in the database if it exists.
218 Implementations should use ``IF EXISTS`` semantics to avoid raising
219 an error if the schema does not exist.
221 Raises
222 ------
223 DatabaseContextError
224 If there is an error dropping the schema.
225 """
226 ...
228 @abstractmethod
229 def create_all(self) -> None:
230 """Create all database objects in the schema using the metadata
231 object.
233 Raises
234 ------
235 DatabaseContextError
236 If there is an error creating the schema objects in the database.
237 """
238 ...
240 @abstractmethod
241 def create_indexes(self) -> None:
242 """Create all indexes in the schema using the metadata object.
244 Raises
245 ------
246 DatabaseContextError
247 If there is an error creating the indexes in the database.
248 """
249 ...
251 @abstractmethod
252 def drop_indexes(self) -> None:
253 """Drop all indexes in the schema using the metadata object.
255 Raises
256 ------
257 DatabaseContextError
258 If there is an error dropping the indexes in the database.
259 """
260 ...
262 @abstractmethod
263 def execute(self, statement: SQLStatement, parameters: dict[str, Any] | None = None) -> Result:
264 """Execute a SQL statement and return the result.
266 Parameters
267 ----------
268 statement
269 The SQL statement to execute.
271 Returns
272 -------
273 `~sqlalchemy.engine.Result`
274 The result of the statement execution.
276 Raises
277 ------
278 DatabaseContextError
279 If there is an error executing the SQL statement.
280 """
281 ...
284class _BaseContext(DatabaseContext):
285 """Base database context providing common behavior.
287 Parameters
288 ----------
289 engine_url
290 The SQLAlchemy engine for connecting to the database.
291 metadata
292 The SQLAlchemy metadata representing the database objects.
293 require_schema
294 True if a valid schema name is required on the MetaData, False if not.
295 """
297 # Subclasses should set this to the dialect name.
298 DIALECT: str
300 def __init__(self, engine_url: URL, metadata: MetaData, require_schema: bool = False) -> None:
301 self._engine_url = engine_url
302 self._metadata = metadata
303 self._schema_name: str | None = metadata.schema
304 self._engine: Engine | None = None
305 self._echo: bool = False
307 # Check that the URL dialect matches this context's expected dialect
308 self._validate_dialect(engine_url)
310 # Ensure the schema name is set for dialects that require it
311 if require_schema and self._schema_name is None:
312 raise DatabaseContextError(f"Schema name must be set for context: {self.dialect_name}")
314 @property
315 def echo(self) -> bool:
316 """Whether to log all SQL statements executed by the engine
317 (``bool``).
318 """
319 return self._echo
321 @echo.setter
322 def echo(self, value: bool) -> None:
323 self._echo = value
324 if self.engine is not None:
325 self.engine.echo = value
327 @classmethod
328 def _validate_dialect(cls, engine_url: URL) -> None:
329 """Validate that the engine dialect matches this context's expected
330 dialect.
332 Parameters
333 ----------
334 engine_url
335 The SQLAlchemy database URL to validate.
337 Raises
338 ------
339 DatabaseContextError
340 If the engine dialect doesn't match the context's expected dialect.
341 """
342 # Normalize both the engine dialect and expected dialect for comparison
343 engine_dialect = _dialect_name(engine_url)
344 expected_dialect = cls.DIALECT.lower()
346 if engine_dialect != expected_dialect:
347 raise DatabaseContextError(
348 f"Engine dialect '{engine_dialect}' does not match the context's expected dialect: "
349 f"{expected_dialect}"
350 )
352 @property
353 def engine(self) -> Engine:
354 if self._engine is None:
355 self._engine = create_engine(self._engine_url)
356 return self._engine
358 @property
359 def metadata(self) -> MetaData:
360 return self._metadata
362 @property
363 def dialect(self) -> Dialect:
364 return self.engine.dialect
366 @property
367 def dialect_name(self) -> str:
368 """Get the dialect name for this database context.
370 Returns
371 -------
372 str
373 The normalized dialect name.
374 """
375 return self.DIALECT
377 @property
378 def schema_name(self) -> str | None:
379 """Effective schema name for this context (may be None).
381 Returns
382 -------
383 str | None
384 The schema name, or None if no schema is set.
385 """
386 return self._schema_name
388 @contextmanager
389 def connect(self) -> Iterator[Connection]:
390 """Context manager for database connection."""
391 with self.engine.connect() as connection:
392 yield connection
394 def execute(self, statement: SQLStatement, parameters: dict[str, Any] | None = None) -> Result:
395 statement = _normalize_statement(statement)
396 try:
397 with self.connect() as conn:
398 with conn.begin():
399 if parameters:
400 result = conn.execute(statement, parameters)
401 else:
402 result = conn.execute(statement)
403 return result
404 except SQLAlchemyError as e:
405 raise DatabaseContextError(f"Error executing statement: {e}") from e
407 def create_all(self) -> None:
408 with self.connect() as conn:
409 with conn.begin():
410 try:
411 self.metadata.create_all(bind=conn)
412 except SQLAlchemyError as e:
413 raise DatabaseContextError(f"Error creating database: {e}") from e
415 def _manage_indexes(self, action: str) -> None:
416 """Manage indexes by creating or dropping them.
418 Parameters
419 ----------
420 action
421 The action to perform, either "create" or "drop".
423 Raises
424 ------
425 DatabaseContextError
426 If there is an error managing the indexes in the database.
427 """
428 with self.connect() as conn:
429 with conn.begin():
430 try:
431 inspector = inspect(conn)
432 for table in self.metadata.tables.values():
433 # Fetch all existing indexes for this table once
434 existing_indexes = _get_existing_indexes(inspector, table.name, self.schema_name)
436 for index in table.indexes:
437 if index.name is None:
438 # Anonymous indexes can't be checked by name
439 logger.warning(f"Skipping anonymous index on table '{table.name}'")
440 continue
442 if action == "create":
443 if index.name in existing_indexes:
444 logger.warning(
445 f"Skipping creation of index '{index.name}' which already exists"
446 )
447 continue
448 index.create(bind=conn, checkfirst=False) # We already checked
449 logger.info(f"Created index '{index.name}'")
450 elif action == "drop":
451 if index.name not in existing_indexes:
452 logger.warning(f"Skipping index '{index.name}' which does not exist")
453 continue
454 index.drop(bind=conn, checkfirst=False) # We already checked
455 logger.info(f"Dropped index '{index.name}'")
456 else:
457 raise ValueError(f"Invalid action '{action}'. Must be 'create' or 'drop'.")
458 except SQLAlchemyError as e:
459 raise DatabaseContextError(f"Error {action}ing indexes: {e}") from e
461 def create_indexes(self) -> None:
462 """Create all indexes in the schema using the metadata object.
464 Raises
465 ------
466 DatabaseContextError
467 If there is an error creating the indexes in the database.
468 """
469 self._manage_indexes("create")
471 def drop_indexes(self) -> None:
472 """Drop all indexes in the schema using the metadata object.
474 Raises
475 ------
476 DatabaseContextError
477 If there is an error dropping the indexes in the database.
478 """
479 self._manage_indexes("drop")
481 def _required_schema_name(self) -> str:
482 """Return the schema name, ensuring that it is set.
484 This is mainly here for typing purposes, because the schema_name
485 property may be None, and mypy doesn't understand that we already
486 checked it during initialization.
487 """
488 if self.schema_name is None:
489 raise DatabaseContextError("Schema name is required but not set.")
490 return self.schema_name
492 def close(self) -> None:
493 """Close and dispose of the database engine."""
494 if self._engine is not None:
495 self._engine.dispose()
496 self._engine = None
499_ContextClass: TypeAlias = type[_BaseContext]
500_ContextDecorator: TypeAlias = Callable[[_ContextClass], _ContextClass]
503class DatabaseContextFactory:
504 """Factory for creating DatabaseContext instances based on dialect type."""
506 _registry: dict[str, _ContextClass] = {}
508 @classmethod
509 def register(cls) -> _ContextDecorator:
510 """Register a context class for its dialect.
512 The dialect is determined by reading the DIALECT attribute from the
513 decorated class.
515 Returns
516 -------
517 Callable
518 The decorator function that registers the context class.
520 Examples
521 --------
522 >>> @DatabaseContextFactory.register()
523 ... class PostgreSQLContext(_BaseContext):
524 ... DIALECT = "postgresql"
525 ... pass
527 Notes
528 -----
529 The registry is populated at module import time and afterwards should
530 be treated as read-only.
531 """
533 def decorator(context_class: type[_BaseContext]) -> type[_BaseContext]:
534 # Get the dialect from the class's DIALECT attribute
535 if not hasattr(context_class, "DIALECT"): 535 ↛ 536line 535 didn't jump to line 536 because the condition on line 535 was never true
536 raise ValueError(f"Context class {context_class.__name__} must define a DIALECT attribute")
537 cls._registry[context_class.DIALECT] = context_class
538 return context_class
540 return decorator
542 @classmethod
543 def register_class(cls, dialect: str, context_class: type[_BaseContext]) -> None:
544 """Register a context class for a specific dialect programmatically.
546 Parameters
547 ----------
548 dialect
549 The dialect name to register.
550 context_class
551 The context class to use for this dialect.
552 """
553 dialect_name = dialect.lower()
554 if "+" in dialect_name:
555 dialect_name = dialect_name.split("+")[0]
556 cls._registry[dialect_name] = context_class
558 @classmethod
559 def create_context(cls, dialect: str, engine_url: URL, metadata: MetaData) -> DatabaseContext:
560 """Create a context instance for the given dialect.
562 Parameters
563 ----------
564 dialect
565 The database dialect name.
566 engine_url
567 The SQLAlchemy database URL.
568 metadata
569 The SQLAlchemy metadata.
571 Returns
572 -------
573 DatabaseContext
574 The appropriate context instance.
576 Raises
577 ------
578 ValueError
579 If no context class is registered for the dialect.
580 """
581 dialect_name = dialect.lower()
582 if "+" in dialect_name:
583 dialect_name = dialect_name.split("+")[0]
585 if dialect_name not in cls._registry:
586 supported = cls.get_supported_dialects()
587 raise ValueError(
588 f"No context class registered for dialect: {dialect_name}. "
589 f"Supported dialects: {', '.join(supported)}"
590 )
592 context_class = cls._registry[dialect_name]
593 return context_class(engine_url, metadata)
595 @classmethod
596 def get_supported_dialects(cls) -> list[str]:
597 """Get a list of supported dialect names.
599 Returns
600 -------
601 list[str]
602 List of supported dialect names.
603 """
604 return list(cls._registry.keys())
607class _SQLWriter:
608 """Write SQL statements to stdout or a file.
610 Parameters
611 ----------
612 file
613 The file to write the SQL statements to. If None, the statements
614 will be written to stdout.
615 """
617 def __init__(self, file: IO[str] | None = None) -> None:
618 """Initialize the SQL writer."""
619 self.file = file
620 self.dialect: Dialect | None = None
622 def write(self, sql: Any, *multiparams: Any, **params: Any) -> None:
623 """Write the SQL statement to a file or stdout.
625 Statements with parameters will be formatted with the values
626 inserted into the resultant SQL output.
628 Parameters
629 ----------
630 sql
631 The SQL statement to write.
632 *multiparams
633 The multiparams to use for the SQL statement.
634 **params
635 The params to use for the SQL statement.
637 Notes
638 -----
639 The functions arguments are typed very loosely because this method in
640 SQLAlchemy is untyped, amd we do not call it directly.
641 """
642 compiled = sql.compile(dialect=self.dialect)
643 sql_str = str(compiled) + ";"
644 params_list = [compiled.params]
645 for params in params_list:
646 if not params:
647 print(sql_str, file=self.file)
648 continue
649 new_params = {}
650 for key, value in params.items():
651 if isinstance(value, str):
652 new_params[key] = f"'{value}'"
653 elif value is None:
654 new_params[key] = "null"
655 else:
656 new_params[key] = value
657 print(sql_str % new_params, file=self.file)
660@DatabaseContextFactory.register()
661class PostgreSQLContext(_BaseContext):
662 """Database context for Postgres.
664 Parameters
665 ----------
666 engine_url
667 The SQLAlchemy database URL for connecting to the database.
668 metadata
669 The SQLAlchemy metadata representing the database objects.
670 """
672 DIALECT = "postgresql"
674 def __init__(self, engine_url: URL, metadata: MetaData):
675 super().__init__(engine_url, metadata, require_schema=True)
677 def initialize(self) -> None:
678 schema_name = self._required_schema_name()
679 try:
680 logger.debug(f"Checking if PG schema exists: {schema_name}")
681 result = self.execute(
682 """
683 SELECT schema_name
684 FROM information_schema.schemata
685 WHERE schema_name = :schema_name
686 """,
687 {"schema_name": schema_name},
688 )
689 if result.fetchone():
690 return
691 logger.debug(f"Creating PG schema: {schema_name}")
692 self.execute(CreateSchema(schema_name))
693 except SQLAlchemyError as e:
694 raise DatabaseContextError(f"Error initializing Postgres schema: {e}") from e
696 def drop(self) -> None:
697 schema_name = self._required_schema_name()
698 try:
699 logger.debug(f"Dropping PostgreSQL schema if exists: {schema_name}")
700 self.execute(DropSchema(schema_name, if_exists=True, cascade=True))
701 except SQLAlchemyError as e:
702 raise DatabaseContextError(f"Error dropping Postgres database: {e}") from e
705@DatabaseContextFactory.register()
706class MySQLContext(_BaseContext):
707 """Database context for MySQL.
709 Parameters
710 ----------
711 engine_url
712 The SQLAlchemy database URL for connecting to the database.
713 metadata
714 The SQLAlchemy metadata representing the database objects.
715 """
717 DIALECT = "mysql"
719 def __init__(self, engine_url: URL, metadata: MetaData):
720 super().__init__(engine_url, metadata, require_schema=True)
722 def initialize(self) -> None:
723 # The schema is instantiated as a database, as MySQL does not have a
724 # distinct schema concept, unlike Postgres.
725 schema_name = self._required_schema_name()
726 try:
727 logger.debug(f"Checking if MySQL database exists: {schema_name}")
728 result = self.execute("SHOW DATABASES LIKE :schema_name", {"schema_name": schema_name})
729 if result.fetchone():
730 return
731 logger.debug(f"Creating MySQL database: {schema_name}")
732 from sqlalchemy import DDL
734 create_stmt = DDL(f"CREATE DATABASE {quoted_name(schema_name, quote=True)}")
735 self.execute(create_stmt)
736 except SQLAlchemyError as e:
737 raise DatabaseContextError(f"Error initializing MySQL database: {e}") from e
739 def drop(self) -> None:
740 schema_name = self._required_schema_name()
741 try:
742 logger.debug(f"Dropping MySQL database if exists: {schema_name}")
743 from sqlalchemy import DDL
745 drop_stmt = DDL(f"DROP DATABASE IF EXISTS {quoted_name(schema_name, quote=True)}")
746 self.execute(drop_stmt)
747 except SQLAlchemyError as e:
748 raise DatabaseContextError(f"Error dropping MySQL database: {e}") from e
751@DatabaseContextFactory.register()
752class SQLiteContext(_BaseContext):
753 """Database context for SQLite.
755 Parameters
756 ----------
757 engine_url
758 The SQLAlchemy database URL for connecting to the database.
759 metadata
760 The SQLAlchemy metadata representing the database objects.
761 """
763 DIALECT = "sqlite"
765 def __init__(self, engine_url: URL, metadata: MetaData):
766 # Schema name needs to be cleared, if set.
767 _clear_schema(metadata)
768 # Schema name is not required.
769 super().__init__(engine_url, metadata)
771 def initialize(self) -> None:
772 # Nothing needs to be done for SQLite initialization.
773 return
775 def drop(self) -> None:
776 try:
777 logger.debug("Dropping tables in SQLite schema")
778 # Drop all the tables in the database file.
779 self.metadata.drop_all(bind=self.engine)
780 except SQLAlchemyError as e:
781 raise DatabaseContextError(f"Error dropping SQLite database: {e}") from e
784class MockContext(DatabaseContext):
785 """Database context for a mock connection.
787 Parameters
788 ----------
789 metadata
790 The SQLAlchemy metadata defining the database objects.
791 connection
792 The SQLAlchemy mock connection.
793 """
795 def __init__(self, metadata: MetaData, connection: MockConnection):
796 self._metadata = metadata
797 self._connection = connection
798 self._dialect = connection.dialect
800 @property
801 def dialect(self) -> Dialect:
802 return self._dialect
804 @property
805 def dialect_name(self) -> str:
806 return self.dialect.name
808 @property
809 def metadata(self) -> MetaData:
810 return self._metadata
812 @property
813 def engine(self) -> Engine:
814 raise DatabaseContextError("MockContext does not provide an engine.")
816 def initialize(self) -> None:
817 # Mock connection doesn't do any initialization.
818 pass
820 def drop(self) -> None:
821 # Mock connection doesn't drop.
822 pass
824 def create_all(self) -> None:
825 self._metadata.create_all(self._connection)
827 def create_indexes(self) -> None:
828 # Mock connection can't create indexes.
829 pass
831 def drop_indexes(self) -> None:
832 # Mock connection can't drop indexes.
833 pass
835 def execute(self, statement: SQLStatement, parameters: dict[str, Any] | None = None) -> Result:
836 statement = _normalize_statement(statement)
837 if parameters:
838 return self._connection.connect().execute(statement, parameters)
839 else:
840 return self._connection.connect().execute(statement)
842 def close(self) -> None:
843 """Close the mock connection (no-op)."""
844 pass
847def create_database_context(
848 engine_url: str | URL,
849 metadata: MetaData,
850 output_file: IO[str] | None = None,
851 dry_run: bool = False,
852 echo: bool | None = None,
853) -> DatabaseContext:
854 """Create a DatabaseContext object based on the engine URL.
856 Parameters
857 ----------
858 engine_url
859 The database URL for the database connection.
860 metadata
861 The SQLAlchemy MetaData representing the database objects.
862 output_file
863 Output file for writing generated SQL commands.
864 dry_run
865 If True, configure the context to perform a dry run, where operations
866 will not be executed.
867 If False, use a normal context where operations are executed.
868 echo
869 If True, the SQLAlchemy engine will log all statements to the console.
871 Returns
872 -------
873 DatabaseContext
874 A database context appropriate for the given engine URL. This will be
875 a `MockContext` if the URL appears like a mock URL or if ``dry_run`` is
876 True, otherwise it will be a context based on the dialect using the
877 factory pattern.
879 Raises
880 ------
881 DatabaseContextError
882 If the dialect is not supported or if there's an issue creating
883 the context.
884 """
885 if isinstance(engine_url, str):
886 engine_url = make_url(engine_url)
888 if is_mock_url(engine_url) or dry_run:
889 # Use a mock context for mock URLs or dry run mode.
890 dialect_name = _dialect_name(engine_url)
891 if dialect_name == "sqlite":
892 _clear_schema(metadata)
893 mock_connection = _create_mock_connection(engine_url, output_file)
894 return MockContext(metadata, mock_connection)
895 else:
896 # Create a real engine and context for the given dialect.
897 try:
898 dialect_name = _dialect_name(engine_url)
900 # Use the factory to create the appropriate context
901 try:
902 db_ctx = DatabaseContextFactory.create_context(dialect_name, engine_url, metadata)
903 if echo is not None:
904 # This is settable for real contexts only.
905 if hasattr(db_ctx, "echo"):
906 db_ctx.echo = echo
907 return db_ctx
908 except ValueError as e:
909 supported = DatabaseContextFactory.get_supported_dialects()
910 raise DatabaseContextError(
911 f"Unsupported dialect: {dialect_name}. Supported dialects are: {', '.join(supported)}"
912 ) from e
914 except Exception as e:
915 if isinstance(e, DatabaseContextError):
916 raise
917 raise DatabaseContextError(f"Failed to create database context: {e}") from e