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type annotations for DB connection

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Sarah Hoffmann
2022-07-01 13:55:24 +02:00
parent 9d716f0f7d
commit e6ee3c772c
1 changed files with 52 additions and 25 deletions
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77
nominatim/db/connection.py
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@@ -7,6 +7,7 @@
"""
Specialised connection and cursor functions.
"""
from typing import Union, List, Optional, Any, Callable, ContextManager, Mapping, cast, TypeVar, overload, Tuple, Sequence
import contextlib
import logging
import os
@@ -18,23 +19,26 @@ from psycopg2 import sql as pysql
from nominatim.errors import UsageError
Query = Union[str, bytes, pysql.Composable]
T = TypeVar('T', bound=psycopg2.extensions.cursor)
LOG = logging.getLogger()
class _Cursor(psycopg2.extras.DictCursor):
""" A cursor returning dict-like objects and providing specialised
execution functions.
"""
# pylint: disable=arguments-renamed,arguments-differ
def execute(self, query, args=None):
def execute(self, query: Query, args: Any = None) -> None:
""" Query execution that logs the SQL query when debugging is enabled.
"""
LOG.debug(self.mogrify(query, args).decode('utf-8'))
if LOG.isEnabledFor(logging.DEBUG):
LOG.debug(self.mogrify(query, args).decode('utf-8')) # type: ignore
super().execute(query, args)
def execute_values(self, sql, argslist, template=None):
def execute_values(self, sql: Query, argslist: List[Any], template: Optional[str] = None) -> None:
""" Wrapper for the psycopg2 convenience function to execute
SQL for a list of values.
"""
@@ -43,7 +47,7 @@ class _Cursor(psycopg2.extras.DictCursor):
psycopg2.extras.execute_values(self, sql, argslist, template=template)
def scalar(self, sql, args=None):
def scalar(self, sql: Query, args: Any = None) -> Any:
""" Execute query that returns a single value. The value is returned.
If the query yields more than one row, a ValueError is raised.
"""
@@ -52,10 +56,13 @@ class _Cursor(psycopg2.extras.DictCursor):
if self.rowcount != 1:
raise RuntimeError("Query did not return a single row.")
return self.fetchone()[0]
result = self.fetchone() # type: ignore
assert result is not None
return result[0]
def drop_table(self, name, if_exists=True, cascade=False):
def drop_table(self, name: str, if_exists: bool = True, cascade: bool = False) -> None:
""" Drop the table with the given name.
Set `if_exists` to False if a non-existant table should raise
an exception instead of just being ignored. If 'cascade' is set
@@ -68,30 +75,41 @@ class _Cursor(psycopg2.extras.DictCursor):
if cascade:
sql += ' CASCADE'
self.execute(pysql.SQL(sql).format(pysql.Identifier(name)))
self.execute(pysql.SQL(sql).format(pysql.Identifier(name))) # type: ignore
class _Connection(psycopg2.extensions.connection):
""" A connection that provides the specialised cursor by default and
adds convenience functions for administrating the database.
"""
@overload # type: ignore[override]
def cursor(self) -> _Cursor:
...
def cursor(self, cursor_factory=_Cursor, **kwargs):
@overload
def cursor(self, name: str) -> _Cursor:
...
@overload
def cursor(self, cursor_factory: Callable[..., T]) -> T:
...
def cursor(self, cursor_factory = _Cursor, **kwargs): # type: ignore
""" Return a new cursor. By default the specialised cursor is returned.
"""
return super().cursor(cursor_factory=cursor_factory, **kwargs)
def table_exists(self, table):
def table_exists(self, table: str) -> bool:
""" Check that a table with the given name exists in the database.
"""
with self.cursor() as cur:
num = cur.scalar("""SELECT count(*) FROM pg_tables
WHERE tablename = %s and schemaname = 'public'""", (table, ))
return num == 1
return num == 1 if isinstance(num, int) else False
def table_has_column(self, table, column):
def table_has_column(self, table: str, column: str) -> bool:
""" Check if the table 'table' exists and has a column with name 'column'.
"""
with self.cursor() as cur:
@@ -99,10 +117,10 @@ class _Connection(psycopg2.extensions.connection):
WHERE table_name = %s
and column_name = %s""",
(table, column))
return has_column > 0
return has_column > 0 if isinstance(has_column, int) else False
def index_exists(self, index, table=None):
def index_exists(self, index: str, table: Optional[str] = None) -> bool:
""" Check that an index with the given name exists in the database.
If table is not None then the index must relate to the given
table.
@@ -114,13 +132,15 @@ class _Connection(psycopg2.extensions.connection):
return False
if table is not None:
row = cur.fetchone()
row = cur.fetchone() # type: ignore
if row is None or not isinstance(row[0], str):
return False
return row[0] == table
return True
def drop_table(self, name, if_exists=True, cascade=False):
def drop_table(self, name: str, if_exists: bool = True, cascade: bool = False) -> None:
""" Drop the table with the given name.
Set `if_exists` to False if a non-existant table should raise
an exception instead of just being ignored.
@@ -130,18 +150,18 @@ class _Connection(psycopg2.extensions.connection):
self.commit()
def server_version_tuple(self):
def server_version_tuple(self) -> Tuple[int, int]:
""" Return the server version as a tuple of (major, minor).
Converts correctly for pre-10 and post-10 PostgreSQL versions.
"""
version = self.server_version
if version < 100000:
return (int(version / 10000), (version % 10000) / 100)
return (int(version / 10000), int((version % 10000) / 100))
return (int(version / 10000), version % 10000)
def postgis_version_tuple(self):
def postgis_version_tuple(self) -> Tuple[int, int]:
""" Return the postgis version installed in the database as a
tuple of (major, minor). Assumes that the PostGIS extension
has been installed already.
@@ -149,10 +169,16 @@ class _Connection(psycopg2.extensions.connection):
with self.cursor() as cur:
version = cur.scalar('SELECT postgis_lib_version()')
return tuple((int(x) for x in version.split('.')[:2]))
version_parts = version.split('.')
if len(version_parts) < 2:
raise UsageError(f"Error fetching Postgis version. Bad format: {version}")
return (int(version_parts[0]), int(version_parts[1]))
def connect(dsn):
class _ConnectionContext(ContextManager[_Connection]):
connection: _Connection
def connect(dsn: str) -> _ConnectionContext:
""" Open a connection to the database using the specialised connection
factory. The returned object may be used in conjunction with 'with'.
When used outside a context manager, use the `connection` attribute
@@ -160,8 +186,8 @@ def connect(dsn):
"""
try:
conn = psycopg2.connect(dsn, connection_factory=_Connection)
ctxmgr = contextlib.closing(conn)
ctxmgr.connection = conn
ctxmgr = cast(_ConnectionContext, contextlib.closing(conn))
ctxmgr.connection = cast(_Connection, conn)
return ctxmgr
except psycopg2.OperationalError as err:
raise UsageError(f"Cannot connect to database: {err}") from err
@@ -199,7 +225,8 @@ _PG_CONNECTION_STRINGS = {
}
def get_pg_env(dsn, base_env=None):
def get_pg_env(dsn: str,
base_env: Optional[Mapping[str, Optional[str]]] = None) -> Mapping[str, Optional[str]]:
""" Return a copy of `base_env` with the environment variables for
PostgresSQL set up from the given database connection string.
If `base_env` is None, then the OS environment is used as a base
@@ -207,7 +234,7 @@ def get_pg_env(dsn, base_env=None):
"""
env = dict(base_env if base_env is not None else os.environ)
for param, value in psycopg2.extensions.parse_dsn(dsn).items():
for param, value in psycopg2.extensions.parse_dsn(dsn).items(): # type: ignore
if param in _PG_CONNECTION_STRINGS:
env[_PG_CONNECTION_STRINGS[param]] = value
else: