266 lines
7.5 KiB
Python
266 lines
7.5 KiB
Python
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"""
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Protocol objects representing different implementations of the same classes.
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"""
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# Copyright (C) 2020 The Psycopg Team
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from typing import Any, Callable, Generator, Mapping
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from typing import List, Optional, Sequence, Tuple, TypeVar, Union
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from typing import TYPE_CHECKING
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from typing_extensions import TypeAlias
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from . import pq
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from ._enums import PyFormat as PyFormat
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from ._compat import Protocol, LiteralString
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if TYPE_CHECKING:
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from . import sql
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from .rows import Row, RowMaker
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from .pq.abc import PGresult
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from .waiting import Wait, Ready
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from .connection import BaseConnection
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from ._adapters_map import AdaptersMap
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NoneType: type = type(None)
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# An object implementing the buffer protocol
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Buffer: TypeAlias = Union[bytes, bytearray, memoryview]
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Query: TypeAlias = Union[LiteralString, bytes, "sql.SQL", "sql.Composed"]
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Params: TypeAlias = Union[Sequence[Any], Mapping[str, Any]]
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ConnectionType = TypeVar("ConnectionType", bound="BaseConnection[Any]")
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PipelineCommand: TypeAlias = Callable[[], None]
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DumperKey: TypeAlias = Union[type, Tuple["DumperKey", ...]]
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# Waiting protocol types
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RV = TypeVar("RV")
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PQGenConn: TypeAlias = Generator[Tuple[int, "Wait"], "Ready", RV]
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"""Generator for processes where the connection file number can change.
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This can happen in connection and reset, but not in normal querying.
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"""
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PQGen: TypeAlias = Generator["Wait", "Ready", RV]
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"""Generator for processes where the connection file number won't change.
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"""
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class WaitFunc(Protocol):
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"""
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Wait on the connection which generated `PQgen` and return its final result.
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"""
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def __call__(
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self, gen: PQGen[RV], fileno: int, timeout: Optional[float] = None
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) -> RV:
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...
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# Adaptation types
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DumpFunc: TypeAlias = Callable[[Any], Buffer]
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LoadFunc: TypeAlias = Callable[[Buffer], Any]
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class AdaptContext(Protocol):
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"""
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A context describing how types are adapted.
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Example of `~AdaptContext` are `~psycopg.Connection`, `~psycopg.Cursor`,
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`~psycopg.adapt.Transformer`, `~psycopg.adapt.AdaptersMap`.
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Note that this is a `~typing.Protocol`, so objects implementing
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`!AdaptContext` don't need to explicitly inherit from this class.
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"""
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@property
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def adapters(self) -> "AdaptersMap":
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"""The adapters configuration that this object uses."""
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...
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@property
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def connection(self) -> Optional["BaseConnection[Any]"]:
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"""The connection used by this object, if available.
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:rtype: `~psycopg.Connection` or `~psycopg.AsyncConnection` or `!None`
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"""
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...
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class Dumper(Protocol):
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"""
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Convert Python objects of type `!cls` to PostgreSQL representation.
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"""
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format: pq.Format
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"""
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The format that this class `dump()` method produces,
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`~psycopg.pq.Format.TEXT` or `~psycopg.pq.Format.BINARY`.
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This is a class attribute.
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"""
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oid: int
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"""The oid to pass to the server, if known; 0 otherwise (class attribute)."""
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def __init__(self, cls: type, context: Optional[AdaptContext] = None):
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...
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def dump(self, obj: Any) -> Buffer:
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"""Convert the object `!obj` to PostgreSQL representation.
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:param obj: the object to convert.
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"""
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...
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def quote(self, obj: Any) -> Buffer:
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"""Convert the object `!obj` to escaped representation.
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:param obj: the object to convert.
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"""
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...
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def get_key(self, obj: Any, format: PyFormat) -> DumperKey:
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"""Return an alternative key to upgrade the dumper to represent `!obj`.
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:param obj: The object to convert
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:param format: The format to convert to
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Normally the type of the object is all it takes to define how to dump
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the object to the database. For instance, a Python `~datetime.date` can
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be simply converted into a PostgreSQL :sql:`date`.
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In a few cases, just the type is not enough. For example:
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- A Python `~datetime.datetime` could be represented as a
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:sql:`timestamptz` or a :sql:`timestamp`, according to whether it
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specifies a `!tzinfo` or not.
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- A Python int could be stored as several Postgres types: int2, int4,
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int8, numeric. If a type too small is used, it may result in an
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overflow. If a type too large is used, PostgreSQL may not want to
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cast it to a smaller type.
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- Python lists should be dumped according to the type they contain to
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convert them to e.g. array of strings, array of ints (and which
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size of int?...)
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In these cases, a dumper can implement `!get_key()` and return a new
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class, or sequence of classes, that can be used to identify the same
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dumper again. If the mechanism is not needed, the method should return
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the same `!cls` object passed in the constructor.
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If a dumper implements `get_key()` it should also implement
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`upgrade()`.
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"""
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...
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def upgrade(self, obj: Any, format: PyFormat) -> "Dumper":
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"""Return a new dumper to manage `!obj`.
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:param obj: The object to convert
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:param format: The format to convert to
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Once `Transformer.get_dumper()` has been notified by `get_key()` that
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this Dumper class cannot handle `!obj` itself, it will invoke
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`!upgrade()`, which should return a new `Dumper` instance, which will
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be reused for every objects for which `!get_key()` returns the same
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result.
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"""
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...
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class Loader(Protocol):
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"""
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Convert PostgreSQL values with type OID `!oid` to Python objects.
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"""
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format: pq.Format
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"""
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The format that this class `load()` method can convert,
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`~psycopg.pq.Format.TEXT` or `~psycopg.pq.Format.BINARY`.
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This is a class attribute.
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"""
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def __init__(self, oid: int, context: Optional[AdaptContext] = None):
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...
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def load(self, data: Buffer) -> Any:
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"""
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Convert the data returned by the database into a Python object.
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:param data: the data to convert.
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"""
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...
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class Transformer(Protocol):
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types: Optional[Tuple[int, ...]]
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formats: Optional[List[pq.Format]]
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def __init__(self, context: Optional[AdaptContext] = None):
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...
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@classmethod
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def from_context(cls, context: Optional[AdaptContext]) -> "Transformer":
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...
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@property
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def connection(self) -> Optional["BaseConnection[Any]"]:
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...
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@property
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def encoding(self) -> str:
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...
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@property
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def adapters(self) -> "AdaptersMap":
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...
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@property
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def pgresult(self) -> Optional["PGresult"]:
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...
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def set_pgresult(
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self,
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result: Optional["PGresult"],
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*,
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set_loaders: bool = True,
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format: Optional[pq.Format] = None
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) -> None:
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...
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def set_dumper_types(self, types: Sequence[int], format: pq.Format) -> None:
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...
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def set_loader_types(self, types: Sequence[int], format: pq.Format) -> None:
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...
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def dump_sequence(
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self, params: Sequence[Any], formats: Sequence[PyFormat]
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) -> Sequence[Optional[Buffer]]:
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...
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def as_literal(self, obj: Any) -> bytes:
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...
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def get_dumper(self, obj: Any, format: PyFormat) -> Dumper:
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...
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def load_rows(self, row0: int, row1: int, make_row: "RowMaker[Row]") -> List["Row"]:
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...
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def load_row(self, row: int, make_row: "RowMaker[Row]") -> Optional["Row"]:
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...
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def load_sequence(self, record: Sequence[Optional[Buffer]]) -> Tuple[Any, ...]:
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...
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def get_loader(self, oid: int, format: pq.Format) -> Loader:
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...
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