codekingpro/portable-devtools

1"""2The Column object in Cursor.description3"""4 5# Copyright (C) 2020 The Psycopg Team6 7from typing import Any, NamedTuple, Optional, Sequence, TYPE_CHECKING8from operator import attrgetter9 10if TYPE_CHECKING:11    from .cursor import BaseCursor12 13 14class ColumnData(NamedTuple):15    ftype: int16    fmod: int17    fsize: int18 19 20class Column(Sequence[Any]):21    __module__ = "psycopg"22 23    def __init__(self, cursor: "BaseCursor[Any, Any]", index: int):24        res = cursor.pgresult25        assert res26 27        fname = res.fname(index)28        if fname:29            self._name = fname.decode(cursor._encoding)30        else:31            # COPY_OUT results have columns but no name32            self._name = f"column_{index + 1}"33 34        self._data = ColumnData(35            ftype=res.ftype(index),36            fmod=res.fmod(index),37            fsize=res.fsize(index),38        )39        self._type = cursor.adapters.types.get(self._data.ftype)40 41    _attrs = tuple(42        attrgetter(attr)43        for attr in """44            name type_code display_size internal_size precision scale null_ok45            """.split()46    )47 48    def __repr__(self) -> str:49        return (50            f"<Column {self.name!r},"51            f" type: {self._type_display()} (oid: {self.type_code})>"52        )53 54    def __len__(self) -> int:55        return 756 57    def _type_display(self) -> str:58        parts = []59        parts.append(self._type.name if self._type else str(self.type_code))60 61        mod1 = self.precision62        if mod1 is None:63            mod1 = self.display_size64        if mod1:65            parts.append(f"({mod1}")66            if self.scale:67                parts.append(f", {self.scale}")68            parts.append(")")69 70        if self._type and self.type_code == self._type.array_oid:71            parts.append("[]")72 73        return "".join(parts)74 75    def __getitem__(self, index: Any) -> Any:76        if isinstance(index, slice):77            return tuple(getter(self) for getter in self._attrs[index])78        else:79            return self._attrs[index](self)80 81    @property82    def name(self) -> str:83        """The name of the column."""84        return self._name85 86    @property87    def type_code(self) -> int:88        """The numeric OID of the column."""89        return self._data.ftype90 91    @property92    def display_size(self) -> Optional[int]:93        """The field size, for :sql:`varchar(n)`, None otherwise."""94        if not self._type:95            return None96 97        if self._type.name in ("varchar", "char"):98            fmod = self._data.fmod99            if fmod >= 0:100                return fmod - 4101 102        return None103 104    @property105    def internal_size(self) -> Optional[int]:106        """The internal field size for fixed-size types, None otherwise."""107        fsize = self._data.fsize108        return fsize if fsize >= 0 else None109 110    @property111    def precision(self) -> Optional[int]:112        """The number of digits for fixed precision types."""113        if not self._type:114            return None115 116        dttypes = ("time", "timetz", "timestamp", "timestamptz", "interval")117        if self._type.name == "numeric":118            fmod = self._data.fmod119            if fmod >= 0:120                return fmod >> 16121 122        elif self._type.name in dttypes:123            fmod = self._data.fmod124            if fmod >= 0:125                return fmod & 0xFFFF126 127        return None128 129    @property130    def scale(self) -> Optional[int]:131        """The number of digits after the decimal point if available."""132        if self._type and self._type.name == "numeric":133            fmod = self._data.fmod - 4134            if fmod >= 0:135                return fmod & 0xFFFF136 137        return None138 139    @property140    def null_ok(self) -> Optional[bool]:141        """Always `!None`"""142        return None143