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