143 lines
3.7 KiB
Python
143 lines
3.7 KiB
Python
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"""
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The Column object in Cursor.description
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"""
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# Copyright (C) 2020 The Psycopg Team
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from typing import Any, NamedTuple, Optional, Sequence, TYPE_CHECKING
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from operator import attrgetter
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if TYPE_CHECKING:
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from .cursor import BaseCursor
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class ColumnData(NamedTuple):
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ftype: int
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fmod: int
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fsize: int
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class Column(Sequence[Any]):
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__module__ = "psycopg"
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def __init__(self, cursor: "BaseCursor[Any, Any]", index: int):
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res = cursor.pgresult
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assert res
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fname = res.fname(index)
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if fname:
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self._name = fname.decode(cursor._encoding)
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else:
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# COPY_OUT results have columns but no name
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self._name = f"column_{index + 1}"
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self._data = ColumnData(
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ftype=res.ftype(index),
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fmod=res.fmod(index),
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fsize=res.fsize(index),
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)
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self._type = cursor.adapters.types.get(self._data.ftype)
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_attrs = tuple(
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attrgetter(attr)
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for attr in """
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name type_code display_size internal_size precision scale null_ok
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""".split()
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)
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def __repr__(self) -> str:
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return (
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f"<Column {self.name!r},"
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f" type: {self._type_display()} (oid: {self.type_code})>"
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)
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def __len__(self) -> int:
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return 7
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def _type_display(self) -> str:
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parts = []
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parts.append(self._type.name if self._type else str(self.type_code))
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mod1 = self.precision
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if mod1 is None:
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mod1 = self.display_size
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if mod1:
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parts.append(f"({mod1}")
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if self.scale:
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parts.append(f", {self.scale}")
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parts.append(")")
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if self._type and self.type_code == self._type.array_oid:
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parts.append("[]")
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return "".join(parts)
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def __getitem__(self, index: Any) -> Any:
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if isinstance(index, slice):
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return tuple(getter(self) for getter in self._attrs[index])
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else:
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return self._attrs[index](self)
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@property
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def name(self) -> str:
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"""The name of the column."""
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return self._name
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@property
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def type_code(self) -> int:
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"""The numeric OID of the column."""
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return self._data.ftype
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@property
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def display_size(self) -> Optional[int]:
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"""The field size, for :sql:`varchar(n)`, None otherwise."""
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if not self._type:
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return None
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if self._type.name in ("varchar", "char"):
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fmod = self._data.fmod
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if fmod >= 0:
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return fmod - 4
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return None
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@property
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def internal_size(self) -> Optional[int]:
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"""The internal field size for fixed-size types, None otherwise."""
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fsize = self._data.fsize
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return fsize if fsize >= 0 else None
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@property
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def precision(self) -> Optional[int]:
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"""The number of digits for fixed precision types."""
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if not self._type:
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return None
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dttypes = ("time", "timetz", "timestamp", "timestamptz", "interval")
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if self._type.name == "numeric":
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fmod = self._data.fmod
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if fmod >= 0:
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return fmod >> 16
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elif self._type.name in dttypes:
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fmod = self._data.fmod
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if fmod >= 0:
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return fmod & 0xFFFF
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return None
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@property
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def scale(self) -> Optional[int]:
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"""The number of digits after the decimal point if available."""
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if self._type and self._type.name == "numeric":
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fmod = self._data.fmod - 4
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if fmod >= 0:
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return fmod & 0xFFFF
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return None
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@property
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def null_ok(self) -> Optional[bool]:
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"""Always `!None`"""
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return None
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