117 lines
3.5 KiB
Python
117 lines
3.5 KiB
Python
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"""
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psycopg two-phase commit support
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"""
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# Copyright (C) 2021 The Psycopg Team
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import re
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import datetime as dt
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from base64 import b64encode, b64decode
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from typing import Optional, Union
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from dataclasses import dataclass, replace
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_re_xid = re.compile(r"^(\d+)_([^_]*)_([^_]*)$")
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@dataclass(frozen=True)
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class Xid:
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"""A two-phase commit transaction identifier.
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The object can also be unpacked as a 3-item tuple (`format_id`, `gtrid`,
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`bqual`).
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"""
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format_id: Optional[int]
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gtrid: str
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bqual: Optional[str]
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prepared: Optional[dt.datetime] = None
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owner: Optional[str] = None
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database: Optional[str] = None
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@classmethod
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def from_string(cls, s: str) -> "Xid":
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"""Try to parse an XA triple from the string.
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This may fail for several reasons. In such case return an unparsed Xid.
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"""
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try:
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return cls._parse_string(s)
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except Exception:
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return Xid(None, s, None)
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def __str__(self) -> str:
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return self._as_tid()
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def __len__(self) -> int:
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return 3
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def __getitem__(self, index: int) -> Union[int, str, None]:
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return (self.format_id, self.gtrid, self.bqual)[index]
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@classmethod
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def _parse_string(cls, s: str) -> "Xid":
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m = _re_xid.match(s)
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if not m:
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raise ValueError("bad Xid format")
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format_id = int(m.group(1))
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gtrid = b64decode(m.group(2)).decode()
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bqual = b64decode(m.group(3)).decode()
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return cls.from_parts(format_id, gtrid, bqual)
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@classmethod
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def from_parts(
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cls, format_id: Optional[int], gtrid: str, bqual: Optional[str]
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) -> "Xid":
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if format_id is not None:
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if bqual is None:
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raise TypeError("if format_id is specified, bqual must be too")
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if not 0 <= format_id < 0x80000000:
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raise ValueError("format_id must be a non-negative 32-bit integer")
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if len(bqual) > 64:
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raise ValueError("bqual must be not longer than 64 chars")
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if len(gtrid) > 64:
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raise ValueError("gtrid must be not longer than 64 chars")
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elif bqual is None:
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raise TypeError("if format_id is None, bqual must be None too")
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return Xid(format_id, gtrid, bqual)
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def _as_tid(self) -> str:
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"""
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Return the PostgreSQL transaction_id for this XA xid.
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PostgreSQL wants just a string, while the DBAPI supports the XA
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standard and thus a triple. We use the same conversion algorithm
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implemented by JDBC in order to allow some form of interoperation.
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see also: the pgjdbc implementation
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http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/jdbc/pgjdbc/org/
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postgresql/xa/RecoveredXid.java?rev=1.2
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"""
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if self.format_id is None or self.bqual is None:
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# Unparsed xid: return the gtrid.
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return self.gtrid
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# XA xid: mash together the components.
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egtrid = b64encode(self.gtrid.encode()).decode()
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ebqual = b64encode(self.bqual.encode()).decode()
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return f"{self.format_id}_{egtrid}_{ebqual}"
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@classmethod
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def _get_recover_query(cls) -> str:
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return "SELECT gid, prepared, owner, database FROM pg_prepared_xacts"
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@classmethod
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def _from_record(
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cls, gid: str, prepared: dt.datetime, owner: str, database: str
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) -> "Xid":
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xid = Xid.from_string(gid)
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return replace(xid, prepared=prepared, owner=owner, database=database)
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Xid.__module__ = "psycopg"
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