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Your IP : 216.73.216.159
"""
The Column object in Cursor.description
"""
# Copyright (C) 2020 The Psycopg Team
from typing import Any, NamedTuple, Optional, Sequence, TYPE_CHECKING
from operator import attrgetter
if TYPE_CHECKING:
from .cursor import BaseCursor
class ColumnData(NamedTuple):
ftype: int
fmod: int
fsize: int
class Column(Sequence[Any]):
__module__ = "psycopg"
def __init__(self, cursor: "BaseCursor[Any, Any]", index: int):
res = cursor.pgresult
assert res
fname = res.fname(index)
if fname:
self._name = fname.decode(cursor._encoding)
else:
# COPY_OUT results have columns but no name
self._name = f"column_{index + 1}"
self._data = ColumnData(
ftype=res.ftype(index),
fmod=res.fmod(index),
fsize=res.fsize(index),
)
self._type = cursor.adapters.types.get(self._data.ftype)
_attrs = tuple(
attrgetter(attr)
for attr in """
name type_code display_size internal_size precision scale null_ok
""".split()
)
def __repr__(self) -> str:
return (
f"<Column {self.name!r},"
f" type: {self._type_display()} (oid: {self.type_code})>"
)
def __len__(self) -> int:
return 7
def _type_display(self) -> str:
parts = []
parts.append(self._type.name if self._type else str(self.type_code))
mod1 = self.precision
if mod1 is None:
mod1 = self.display_size
if mod1:
parts.append(f"({mod1}")
if self.scale:
parts.append(f", {self.scale}")
parts.append(")")
if self._type and self.type_code == self._type.array_oid:
parts.append("[]")
return "".join(parts)
def __getitem__(self, index: Any) -> Any:
if isinstance(index, slice):
return tuple(getter(self) for getter in self._attrs[index])
else:
return self._attrs[index](self)
@property
def name(self) -> str:
"""The name of the column."""
return self._name
@property
def type_code(self) -> int:
"""The numeric OID of the column."""
return self._data.ftype
@property
def display_size(self) -> Optional[int]:
"""The field size, for :sql:`varchar(n)`, None otherwise."""
if not self._type:
return None
if self._type.name in ("varchar", "char"):
fmod = self._data.fmod
if fmod >= 0:
return fmod - 4
return None
@property
def internal_size(self) -> Optional[int]:
"""The internal field size for fixed-size types, None otherwise."""
fsize = self._data.fsize
return fsize if fsize >= 0 else None
@property
def precision(self) -> Optional[int]:
"""The number of digits for fixed precision types."""
if not self._type:
return None
dttypes = ("time", "timetz", "timestamp", "timestamptz", "interval")
if self._type.name == "numeric":
fmod = self._data.fmod
if fmod >= 0:
return fmod >> 16
elif self._type.name in dttypes:
fmod = self._data.fmod
if fmod >= 0:
return fmod & 0xFFFF
return None
@property
def scale(self) -> Optional[int]:
"""The number of digits after the decimal point if available."""
if self._type and self._type.name == "numeric":
fmod = self._data.fmod - 4
if fmod >= 0:
return fmod & 0xFFFF
return None
@property
def null_ok(self) -> Optional[bool]:
"""Always `!None`"""
return None