321 lines
9.0 KiB
Python
321 lines
9.0 KiB
Python
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"""
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Generators implementing communication protocols with the libpq
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Certain operations (connection, querying) are an interleave of libpq calls and
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waiting for the socket to be ready. This module contains the code to execute
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the operations, yielding a polling state whenever there is to wait. The
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functions in the `waiting` module are the ones who wait more or less
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cooperatively for the socket to be ready and make these generators continue.
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All these generators yield pairs (fileno, `Wait`) whenever an operation would
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block. The generator can be restarted sending the appropriate `Ready` state
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when the file descriptor is ready.
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"""
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# Copyright (C) 2020 The Psycopg Team
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import logging
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from typing import List, Optional, Union
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from . import pq
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from . import errors as e
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from .abc import Buffer, PipelineCommand, PQGen, PQGenConn
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from .pq.abc import PGconn, PGresult
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from .waiting import Wait, Ready
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from ._compat import Deque
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from ._cmodule import _psycopg
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from ._encodings import pgconn_encoding, conninfo_encoding
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OK = pq.ConnStatus.OK
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BAD = pq.ConnStatus.BAD
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POLL_OK = pq.PollingStatus.OK
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POLL_READING = pq.PollingStatus.READING
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POLL_WRITING = pq.PollingStatus.WRITING
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POLL_FAILED = pq.PollingStatus.FAILED
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COMMAND_OK = pq.ExecStatus.COMMAND_OK
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COPY_OUT = pq.ExecStatus.COPY_OUT
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COPY_IN = pq.ExecStatus.COPY_IN
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COPY_BOTH = pq.ExecStatus.COPY_BOTH
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PIPELINE_SYNC = pq.ExecStatus.PIPELINE_SYNC
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WAIT_R = Wait.R
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WAIT_W = Wait.W
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WAIT_RW = Wait.RW
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READY_R = Ready.R
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READY_W = Ready.W
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READY_RW = Ready.RW
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logger = logging.getLogger(__name__)
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def _connect(conninfo: str) -> PQGenConn[PGconn]:
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"""
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Generator to create a database connection without blocking.
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"""
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conn = pq.PGconn.connect_start(conninfo.encode())
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while True:
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if conn.status == BAD:
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encoding = conninfo_encoding(conninfo)
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raise e.OperationalError(
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f"connection is bad: {pq.error_message(conn, encoding=encoding)}",
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pgconn=conn,
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)
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status = conn.connect_poll()
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if status == POLL_OK:
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break
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elif status == POLL_READING:
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yield conn.socket, WAIT_R
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elif status == POLL_WRITING:
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yield conn.socket, WAIT_W
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elif status == POLL_FAILED:
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encoding = conninfo_encoding(conninfo)
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raise e.OperationalError(
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f"connection failed: {pq.error_message(conn, encoding=encoding)}",
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pgconn=conn,
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)
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else:
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raise e.InternalError(f"unexpected poll status: {status}", pgconn=conn)
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conn.nonblocking = 1
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return conn
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def _execute(pgconn: PGconn) -> PQGen[List[PGresult]]:
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"""
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Generator sending a query and returning results without blocking.
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The query must have already been sent using `pgconn.send_query()` or
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similar. Flush the query and then return the result using nonblocking
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functions.
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Return the list of results returned by the database (whether success
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or error).
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"""
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yield from _send(pgconn)
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rv = yield from _fetch_many(pgconn)
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return rv
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def _send(pgconn: PGconn) -> PQGen[None]:
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"""
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Generator to send a query to the server without blocking.
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The query must have already been sent using `pgconn.send_query()` or
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similar. Flush the query and then return the result using nonblocking
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functions.
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After this generator has finished you may want to cycle using `fetch()`
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to retrieve the results available.
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"""
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while True:
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f = pgconn.flush()
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if f == 0:
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break
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ready = yield WAIT_RW
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if ready & READY_R:
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# This call may read notifies: they will be saved in the
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# PGconn buffer and passed to Python later, in `fetch()`.
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pgconn.consume_input()
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def _fetch_many(pgconn: PGconn) -> PQGen[List[PGresult]]:
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"""
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Generator retrieving results from the database without blocking.
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The query must have already been sent to the server, so pgconn.flush() has
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already returned 0.
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Return the list of results returned by the database (whether success
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or error).
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"""
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results: List[PGresult] = []
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while True:
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res = yield from _fetch(pgconn)
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if not res:
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break
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results.append(res)
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status = res.status
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if status == COPY_IN or status == COPY_OUT or status == COPY_BOTH:
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# After entering copy mode the libpq will create a phony result
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# for every request so let's break the endless loop.
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break
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if status == PIPELINE_SYNC:
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# PIPELINE_SYNC is not followed by a NULL, but we return it alone
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# similarly to other result sets.
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assert len(results) == 1, results
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break
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return results
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def _fetch(pgconn: PGconn) -> PQGen[Optional[PGresult]]:
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"""
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Generator retrieving a single result from the database without blocking.
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The query must have already been sent to the server, so pgconn.flush() has
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already returned 0.
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Return a result from the database (whether success or error).
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"""
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if pgconn.is_busy():
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yield WAIT_R
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while True:
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pgconn.consume_input()
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if not pgconn.is_busy():
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break
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yield WAIT_R
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_consume_notifies(pgconn)
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return pgconn.get_result()
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def _pipeline_communicate(
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pgconn: PGconn, commands: Deque[PipelineCommand]
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) -> PQGen[List[List[PGresult]]]:
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"""Generator to send queries from a connection in pipeline mode while also
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receiving results.
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Return a list results, including single PIPELINE_SYNC elements.
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"""
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results = []
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while True:
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ready = yield WAIT_RW
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if ready & READY_R:
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pgconn.consume_input()
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_consume_notifies(pgconn)
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res: List[PGresult] = []
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while not pgconn.is_busy():
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r = pgconn.get_result()
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if r is None:
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if not res:
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break
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results.append(res)
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res = []
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elif r.status == PIPELINE_SYNC:
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assert not res
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results.append([r])
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else:
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res.append(r)
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if ready & READY_W:
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pgconn.flush()
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if not commands:
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break
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commands.popleft()()
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return results
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def _consume_notifies(pgconn: PGconn) -> None:
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# Consume notifies
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while True:
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n = pgconn.notifies()
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if not n:
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break
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if pgconn.notify_handler:
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pgconn.notify_handler(n)
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def notifies(pgconn: PGconn) -> PQGen[List[pq.PGnotify]]:
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yield WAIT_R
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pgconn.consume_input()
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ns = []
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while True:
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n = pgconn.notifies()
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if n:
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ns.append(n)
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else:
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break
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return ns
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def copy_from(pgconn: PGconn) -> PQGen[Union[memoryview, PGresult]]:
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while True:
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nbytes, data = pgconn.get_copy_data(1)
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if nbytes != 0:
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break
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# would block
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yield WAIT_R
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pgconn.consume_input()
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if nbytes > 0:
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# some data
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return data
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# Retrieve the final result of copy
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results = yield from _fetch_many(pgconn)
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if len(results) > 1:
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# TODO: too brutal? Copy worked.
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raise e.ProgrammingError("you cannot mix COPY with other operations")
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result = results[0]
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if result.status != COMMAND_OK:
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encoding = pgconn_encoding(pgconn)
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raise e.error_from_result(result, encoding=encoding)
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return result
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def copy_to(pgconn: PGconn, buffer: Buffer) -> PQGen[None]:
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# Retry enqueuing data until successful.
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#
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# WARNING! This can cause an infinite loop if the buffer is too large. (see
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# ticket #255). We avoid it in the Copy object by splitting a large buffer
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# into smaller ones. We prefer to do it there instead of here in order to
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# do it upstream the queue decoupling the writer task from the producer one.
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while pgconn.put_copy_data(buffer) == 0:
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yield WAIT_W
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def copy_end(pgconn: PGconn, error: Optional[bytes]) -> PQGen[PGresult]:
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# Retry enqueuing end copy message until successful
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while pgconn.put_copy_end(error) == 0:
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yield WAIT_W
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# Repeat until it the message is flushed to the server
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while True:
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yield WAIT_W
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f = pgconn.flush()
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if f == 0:
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break
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# Retrieve the final result of copy
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(result,) = yield from _fetch_many(pgconn)
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if result.status != COMMAND_OK:
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encoding = pgconn_encoding(pgconn)
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raise e.error_from_result(result, encoding=encoding)
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return result
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# Override functions with fast versions if available
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if _psycopg:
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connect = _psycopg.connect
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execute = _psycopg.execute
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send = _psycopg.send
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fetch_many = _psycopg.fetch_many
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fetch = _psycopg.fetch
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pipeline_communicate = _psycopg.pipeline_communicate
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else:
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connect = _connect
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execute = _execute
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send = _send
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fetch_many = _fetch_many
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fetch = _fetch
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pipeline_communicate = _pipeline_communicate
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