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Your IP : 216.73.216.223
"""
psycopg server-side cursor objects.
"""
# Copyright (C) 2020 The Psycopg Team
from typing import Any, AsyncIterator, List, Iterable, Iterator
from typing import Optional, TypeVar, TYPE_CHECKING, overload
from warnings import warn
from . import pq
from . import sql
from . import errors as e
from .abc import ConnectionType, Query, Params, PQGen
from .rows import Row, RowFactory, AsyncRowFactory
from .cursor import BaseCursor, Cursor
from .generators import execute
from .cursor_async import AsyncCursor
if TYPE_CHECKING:
from .connection import Connection
from .connection_async import AsyncConnection
DEFAULT_ITERSIZE = 100
TEXT = pq.Format.TEXT
BINARY = pq.Format.BINARY
COMMAND_OK = pq.ExecStatus.COMMAND_OK
TUPLES_OK = pq.ExecStatus.TUPLES_OK
IDLE = pq.TransactionStatus.IDLE
INTRANS = pq.TransactionStatus.INTRANS
class ServerCursorMixin(BaseCursor[ConnectionType, Row]):
"""Mixin to add ServerCursor behaviour and implementation a BaseCursor."""
__slots__ = "_name _scrollable _withhold _described itersize _format".split()
def __init__(
self,
name: str,
scrollable: Optional[bool],
withhold: bool,
):
self._name = name
self._scrollable = scrollable
self._withhold = withhold
self._described = False
self.itersize: int = DEFAULT_ITERSIZE
self._format = TEXT
def __repr__(self) -> str:
# Insert the name as the second word
parts = super().__repr__().split(None, 1)
parts.insert(1, f"{self._name!r}")
return " ".join(parts)
@property
def name(self) -> str:
"""The name of the cursor."""
return self._name
@property
def scrollable(self) -> Optional[bool]:
"""
Whether the cursor is scrollable or not.
If `!None` leave the choice to the server. Use `!True` if you want to
use `scroll()` on the cursor.
"""
return self._scrollable
@property
def withhold(self) -> bool:
"""
If the cursor can be used after the creating transaction has committed.
"""
return self._withhold
@property
def rownumber(self) -> Optional[int]:
"""Index of the next row to fetch in the current result.
`!None` if there is no result to fetch.
"""
res = self.pgresult
# command_status is empty if the result comes from
# describe_portal, which means that we have just executed the DECLARE,
# so we can assume we are at the first row.
tuples = res and (res.status == TUPLES_OK or res.command_status == b"")
return self._pos if tuples else None
def _declare_gen(
self,
query: Query,
params: Optional[Params] = None,
binary: Optional[bool] = None,
) -> PQGen[None]:
"""Generator implementing `ServerCursor.execute()`."""
query = self._make_declare_statement(query)
# If the cursor is being reused, the previous one must be closed.
if self._described:
yield from self._close_gen()
self._described = False
yield from self._start_query(query)
pgq = self._convert_query(query, params)
self._execute_send(pgq, force_extended=True)
results = yield from execute(self._conn.pgconn)
if results[-1].status != COMMAND_OK:
self._raise_for_result(results[-1])
# Set the format, which will be used by describe and fetch operations
if binary is None:
self._format = self.format
else:
self._format = BINARY if binary else TEXT
# The above result only returned COMMAND_OK. Get the cursor shape
yield from self._describe_gen()
def _describe_gen(self) -> PQGen[None]:
self._pgconn.send_describe_portal(self._name.encode(self._encoding))
results = yield from execute(self._pgconn)
self._check_results(results)
self._results = results
self._select_current_result(0, format=self._format)
self._described = True
def _close_gen(self) -> PQGen[None]:
ts = self._conn.pgconn.transaction_status
# if the connection is not in a sane state, don't even try
if ts != IDLE and ts != INTRANS:
return
# If we are IDLE, a WITHOUT HOLD cursor will surely have gone already.
if not self._withhold and ts == IDLE:
return
# if we didn't declare the cursor ourselves we still have to close it
# but we must make sure it exists.
if not self._described:
query = sql.SQL(
"SELECT 1 FROM pg_catalog.pg_cursors WHERE name = {}"
).format(sql.Literal(self._name))
res = yield from self._conn._exec_command(query)
# pipeline mode otherwise, unsupported here.
assert res is not None
if res.ntuples == 0:
return
query = sql.SQL("CLOSE {}").format(sql.Identifier(self._name))
yield from self._conn._exec_command(query)
def _fetch_gen(self, num: Optional[int]) -> PQGen[List[Row]]:
if self.closed:
raise e.InterfaceError("the cursor is closed")
# If we are stealing the cursor, make sure we know its shape
if not self._described:
yield from self._start_query()
yield from self._describe_gen()
query = sql.SQL("FETCH FORWARD {} FROM {}").format(
sql.SQL("ALL") if num is None else sql.Literal(num),
sql.Identifier(self._name),
)
res = yield from self._conn._exec_command(query, result_format=self._format)
# pipeline mode otherwise, unsupported here.
assert res is not None
self.pgresult = res
self._tx.set_pgresult(res, set_loaders=False)
return self._tx.load_rows(0, res.ntuples, self._make_row)
def _scroll_gen(self, value: int, mode: str) -> PQGen[None]:
if mode not in ("relative", "absolute"):
raise ValueError(f"bad mode: {mode}. It should be 'relative' or 'absolute'")
query = sql.SQL("MOVE{} {} FROM {}").format(
sql.SQL(" ABSOLUTE" if mode == "absolute" else ""),
sql.Literal(value),
sql.Identifier(self._name),
)
yield from self._conn._exec_command(query)
def _make_declare_statement(self, query: Query) -> sql.Composed:
if isinstance(query, bytes):
query = query.decode(self._encoding)
if not isinstance(query, sql.Composable):
query = sql.SQL(query)
parts = [
sql.SQL("DECLARE"),
sql.Identifier(self._name),
]
if self._scrollable is not None:
parts.append(sql.SQL("SCROLL" if self._scrollable else "NO SCROLL"))
parts.append(sql.SQL("CURSOR"))
if self._withhold:
parts.append(sql.SQL("WITH HOLD"))
parts.append(sql.SQL("FOR"))
parts.append(query)
return sql.SQL(" ").join(parts)
class ServerCursor(ServerCursorMixin["Connection[Any]", Row], Cursor[Row]):
__module__ = "psycopg"
__slots__ = ()
_Self = TypeVar("_Self", bound="ServerCursor[Any]")
@overload
def __init__(
self: "ServerCursor[Row]",
connection: "Connection[Row]",
name: str,
*,
scrollable: Optional[bool] = None,
withhold: bool = False,
):
...
@overload
def __init__(
self: "ServerCursor[Row]",
connection: "Connection[Any]",
name: str,
*,
row_factory: RowFactory[Row],
scrollable: Optional[bool] = None,
withhold: bool = False,
):
...
def __init__(
self,
connection: "Connection[Any]",
name: str,
*,
row_factory: Optional[RowFactory[Row]] = None,
scrollable: Optional[bool] = None,
withhold: bool = False,
):
Cursor.__init__(
self, connection, row_factory=row_factory or connection.row_factory
)
ServerCursorMixin.__init__(self, name, scrollable, withhold)
def __del__(self) -> None:
if not self.closed:
warn(
f"the server-side cursor {self} was deleted while still open."
" Please use 'with' or '.close()' to close the cursor properly",
ResourceWarning,
)
def close(self) -> None:
"""
Close the current cursor and free associated resources.
"""
with self._conn.lock:
if self.closed:
return
if not self._conn.closed:
self._conn.wait(self._close_gen())
super().close()
def execute(
self: _Self,
query: Query,
params: Optional[Params] = None,
*,
binary: Optional[bool] = None,
**kwargs: Any,
) -> _Self:
"""
Open a cursor to execute a query to the database.
"""
if kwargs:
raise TypeError(f"keyword not supported: {list(kwargs)[0]}")
if self._pgconn.pipeline_status:
raise e.NotSupportedError(
"server-side cursors not supported in pipeline mode"
)
try:
with self._conn.lock:
self._conn.wait(self._declare_gen(query, params, binary))
except e._NO_TRACEBACK as ex:
raise ex.with_traceback(None)
return self
def executemany(
self,
query: Query,
params_seq: Iterable[Params],
*,
returning: bool = True,
) -> None:
"""Method not implemented for server-side cursors."""
raise e.NotSupportedError("executemany not supported on server-side cursors")
def fetchone(self) -> Optional[Row]:
with self._conn.lock:
recs = self._conn.wait(self._fetch_gen(1))
if recs:
self._pos += 1
return recs[0]
else:
return None
def fetchmany(self, size: int = 0) -> List[Row]:
if not size:
size = self.arraysize
with self._conn.lock:
recs = self._conn.wait(self._fetch_gen(size))
self._pos += len(recs)
return recs
def fetchall(self) -> List[Row]:
with self._conn.lock:
recs = self._conn.wait(self._fetch_gen(None))
self._pos += len(recs)
return recs
def __iter__(self) -> Iterator[Row]:
while True:
with self._conn.lock:
recs = self._conn.wait(self._fetch_gen(self.itersize))
for rec in recs:
self._pos += 1
yield rec
if len(recs) < self.itersize:
break
def scroll(self, value: int, mode: str = "relative") -> None:
with self._conn.lock:
self._conn.wait(self._scroll_gen(value, mode))
# Postgres doesn't have a reliable way to report a cursor out of bound
if mode == "relative":
self._pos += value
else:
self._pos = value
class AsyncServerCursor(
ServerCursorMixin["AsyncConnection[Any]", Row], AsyncCursor[Row]
):
__module__ = "psycopg"
__slots__ = ()
_Self = TypeVar("_Self", bound="AsyncServerCursor[Any]")
@overload
def __init__(
self: "AsyncServerCursor[Row]",
connection: "AsyncConnection[Row]",
name: str,
*,
scrollable: Optional[bool] = None,
withhold: bool = False,
):
...
@overload
def __init__(
self: "AsyncServerCursor[Row]",
connection: "AsyncConnection[Any]",
name: str,
*,
row_factory: AsyncRowFactory[Row],
scrollable: Optional[bool] = None,
withhold: bool = False,
):
...
def __init__(
self,
connection: "AsyncConnection[Any]",
name: str,
*,
row_factory: Optional[AsyncRowFactory[Row]] = None,
scrollable: Optional[bool] = None,
withhold: bool = False,
):
AsyncCursor.__init__(
self, connection, row_factory=row_factory or connection.row_factory
)
ServerCursorMixin.__init__(self, name, scrollable, withhold)
def __del__(self) -> None:
if not self.closed:
warn(
f"the server-side cursor {self} was deleted while still open."
" Please use 'with' or '.close()' to close the cursor properly",
ResourceWarning,
)
async def close(self) -> None:
async with self._conn.lock:
if self.closed:
return
if not self._conn.closed:
await self._conn.wait(self._close_gen())
await super().close()
async def execute(
self: _Self,
query: Query,
params: Optional[Params] = None,
*,
binary: Optional[bool] = None,
**kwargs: Any,
) -> _Self:
if kwargs:
raise TypeError(f"keyword not supported: {list(kwargs)[0]}")
if self._pgconn.pipeline_status:
raise e.NotSupportedError(
"server-side cursors not supported in pipeline mode"
)
try:
async with self._conn.lock:
await self._conn.wait(self._declare_gen(query, params, binary))
except e._NO_TRACEBACK as ex:
raise ex.with_traceback(None)
return self
async def executemany(
self,
query: Query,
params_seq: Iterable[Params],
*,
returning: bool = True,
) -> None:
raise e.NotSupportedError("executemany not supported on server-side cursors")
async def fetchone(self) -> Optional[Row]:
async with self._conn.lock:
recs = await self._conn.wait(self._fetch_gen(1))
if recs:
self._pos += 1
return recs[0]
else:
return None
async def fetchmany(self, size: int = 0) -> List[Row]:
if not size:
size = self.arraysize
async with self._conn.lock:
recs = await self._conn.wait(self._fetch_gen(size))
self._pos += len(recs)
return recs
async def fetchall(self) -> List[Row]:
async with self._conn.lock:
recs = await self._conn.wait(self._fetch_gen(None))
self._pos += len(recs)
return recs
async def __aiter__(self) -> AsyncIterator[Row]:
while True:
async with self._conn.lock:
recs = await self._conn.wait(self._fetch_gen(self.itersize))
for rec in recs:
self._pos += 1
yield rec
if len(recs) < self.itersize:
break
async def scroll(self, value: int, mode: str = "relative") -> None:
async with self._conn.lock:
await self._conn.wait(self._scroll_gen(value, mode))