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"""
psycopg libpq wrapper
This package exposes the libpq functionalities as Python objects and functions.
The real implementation (the binding to the C library) is
implementation-dependant but all the implementations share the same interface.
"""
# Copyright (C) 2020 The Psycopg Team
import os
import logging
from typing import Callable, List, Type
from . import abc
from .misc import ConninfoOption, PGnotify, PGresAttDesc
from .misc import error_message
from ._enums import ConnStatus, DiagnosticField, ExecStatus, Format, Trace
from ._enums import Ping, PipelineStatus, PollingStatus, TransactionStatus
logger = logging.getLogger(__name__)
__impl__: str
"""The currently loaded implementation of the `!psycopg.pq` package.
Possible values include ``python``, ``c``, ``binary``.
"""
__build_version__: int
"""The libpq version the C package was built with.
A number in the same format of `~psycopg.ConnectionInfo.server_version`
representing the libpq used to build the speedup module (``c``, ``binary``) if
available.
Certain features might not be available if the built version is too old.
"""
version: Callable[[], int]
PGconn: Type[abc.PGconn]
PGresult: Type[abc.PGresult]
Conninfo: Type[abc.Conninfo]
Escaping: Type[abc.Escaping]
PGcancel: Type[abc.PGcancel]
def import_from_libpq() -> None:
"""
Import pq objects implementation from the best libpq wrapper available.
If an implementation is requested try to import only it, otherwise
try to import the best implementation available.
"""
# import these names into the module on success as side effect
global __impl__, version, __build_version__
global PGconn, PGresult, Conninfo, Escaping, PGcancel
impl = os.environ.get("PSYCOPG_IMPL", "").lower()
module = None
attempts: List[str] = []
def handle_error(name: str, e: Exception) -> None:
if not impl:
msg = f"couldn't import psycopg '{name}' implementation: {e}"
logger.debug(msg)
attempts.append(msg)
else:
msg = f"couldn't import requested psycopg '{name}' implementation: {e}"
raise ImportError(msg) from e
# The best implementation: fast but requires the system libpq installed
if not impl or impl == "c":
try:
from psycopg_c import pq as module # type: ignore
except Exception as e:
handle_error("c", e)
# Second best implementation: fast and stand-alone
if not module and (not impl or impl == "binary"):
try:
from psycopg_binary import pq as module # type: ignore
except Exception as e:
handle_error("binary", e)
# Pure Python implementation, slow and requires the system libpq installed.
if not module and (not impl or impl == "python"):
try:
from . import pq_ctypes as module # type: ignore[assignment]
except Exception as e:
handle_error("python", e)
if module:
__impl__ = module.__impl__
version = module.version
PGconn = module.PGconn
PGresult = module.PGresult
Conninfo = module.Conninfo
Escaping = module.Escaping
PGcancel = module.PGcancel
__build_version__ = module.__build_version__
elif impl:
raise ImportError(f"requested psycopg implementation '{impl}' unknown")
else:
sattempts = "\n".join(f"- {attempt}" for attempt in attempts)
raise ImportError(
f"""\
no pq wrapper available.
Attempts made:
{sattempts}"""
)
import_from_libpq()
__all__ = (
"ConnStatus",
"PipelineStatus",
"PollingStatus",
"TransactionStatus",
"ExecStatus",
"Ping",
"DiagnosticField",
"Format",
"Trace",
"PGconn",
"PGnotify",
"Conninfo",
"PGresAttDesc",
"error_message",
"ConninfoOption",
"version",
)