447 lines
14 KiB
Python
447 lines
14 KiB
Python
import weakref
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from collections.abc import Mapping, Sequence
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from sqlalchemy.sql import expression, sqltypes
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from . import exc
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from .utils import SQLALCHEMY_VERSION
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if SQLALCHEMY_VERSION >= ["1", "4"]:
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from sqlalchemy.util import string_or_unprintable
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else:
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from sqlalchemy.sql.expression import (
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_string_or_unprintable as string_or_unprintable,
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)
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class RowProxy(Mapping):
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__slots__ = ("_result_proxy", "_row", "_processors", "_keymap")
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def __init__(self, result_proxy, row, processors, keymap):
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"""RowProxy objects are constructed by ResultProxy objects."""
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self._result_proxy = result_proxy
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self._row = row
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self._processors = processors
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self._keymap = keymap
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def __iter__(self):
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return iter(self._result_proxy.keys)
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def __len__(self):
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return len(self._row)
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def __getitem__(self, key):
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try:
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processor, obj, index = self._keymap[key]
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except KeyError:
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processor, obj, index = self._result_proxy._key_fallback(key)
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# Do we need slicing at all? RowProxy now is Mapping not Sequence
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# except TypeError:
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# if isinstance(key, slice):
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# l = []
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# for processor, value in zip(self._processors[key],
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# self._row[key]):
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# if processor is None:
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# l.append(value)
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# else:
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# l.append(processor(value))
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# return tuple(l)
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# else:
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# raise
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if index is None:
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raise exc.InvalidRequestError(
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f"Ambiguous column name {key!r} in result set! "
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f"try 'use_labels' option on select statement."
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)
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if processor is not None:
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return processor(self._row[index])
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else:
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return self._row[index]
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def __getattr__(self, name):
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try:
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return self[name]
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except KeyError as e:
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raise AttributeError(e.args[0])
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def __contains__(self, key):
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return self._result_proxy._has_key(self._row, key)
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__hash__ = None
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def __eq__(self, other):
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if isinstance(other, RowProxy):
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return self.as_tuple() == other.as_tuple()
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elif isinstance(other, Sequence):
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return self.as_tuple() == other
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else:
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return NotImplemented
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def __ne__(self, other):
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return not self == other
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def as_tuple(self):
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return tuple(self[k] for k in self)
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def __repr__(self):
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return repr(self.as_tuple())
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class ResultMetaData:
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"""Handle cursor.description, applying additional info from an execution
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context."""
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def __init__(self, result_proxy, cursor_description):
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self._processors = processors = []
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map_type, map_column_name = self.result_map(result_proxy._result_map)
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# We do not strictly need to store the processor in the key mapping,
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# though it is faster in the Python version (probably because of the
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# saved attribute lookup self._processors)
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self._keymap = keymap = {}
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self.keys = []
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dialect = result_proxy.dialect
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# `dbapi_type_map` property removed in SQLAlchemy 1.2+.
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# Usage of `getattr` only needed for backward compatibility with
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# older versions of SQLAlchemy.
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typemap = getattr(dialect, "dbapi_type_map", {})
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assert (
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dialect.case_sensitive
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), "Doesn't support case insensitive database connection"
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# high precedence key values.
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primary_keymap = {}
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assert (
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not dialect.description_encoding
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), "psycopg in py3k should not use this"
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for i, rec in enumerate(cursor_description):
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colname = rec[0]
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coltype = rec[1]
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# PostgreSQL doesn't require this.
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# if dialect.requires_name_normalize:
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# colname = dialect.normalize_name(colname)
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name, obj, type_ = (
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map_column_name.get(colname, colname),
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None,
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map_type.get(colname, typemap.get(coltype, sqltypes.NULLTYPE)),
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)
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processor = type_._cached_result_processor(dialect, coltype)
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processors.append(processor)
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rec = (processor, obj, i)
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# indexes as keys. This is only needed for the Python version of
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# RowProxy (the C version uses a faster path for integer indexes).
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primary_keymap[i] = rec
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# populate primary keymap, looking for conflicts.
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if primary_keymap.setdefault(name, rec) != rec:
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# place a record that doesn't have the "index" - this
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# is interpreted later as an AmbiguousColumnError,
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# but only when actually accessed. Columns
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# colliding by name is not a problem if those names
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# aren't used; integer access is always
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# unambiguous.
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primary_keymap[name] = rec = (None, obj, None)
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self.keys.append(name)
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if obj:
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for o in obj:
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keymap[o] = rec
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# technically we should be doing this but we
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# are saving on callcounts by not doing so.
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# if keymap.setdefault(o, rec) is not rec:
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# keymap[o] = (None, obj, None)
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# overwrite keymap values with those of the
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# high precedence keymap.
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keymap.update(primary_keymap)
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def result_map(self, data_map):
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data_map = data_map or {}
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map_type = {}
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map_column_name = {}
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for elem in data_map:
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name = elem[0]
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priority_name = getattr(elem[2][0], "key", None) or name
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map_type[name] = elem[3] # type column
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map_column_name[name] = priority_name
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return map_type, map_column_name
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def _key_fallback(self, key, raiseerr=True):
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map = self._keymap
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result = None
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if isinstance(key, str):
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result = map.get(key)
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# fallback for targeting a ColumnElement to a textual expression
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# this is a rare use case which only occurs when matching text()
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# or colummn('name') constructs to ColumnElements, or after a
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# pickle/unpickle roundtrip
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elif isinstance(key, expression.ColumnElement):
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if key._label and key._label in map:
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result = map[key._label]
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elif hasattr(key, "key") and key.key in map:
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# match is only on name.
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result = map[key.key]
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# search extra hard to make sure this
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# isn't a column/label name overlap.
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# this check isn't currently available if the row
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# was unpickled.
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if result is not None and result[1] is not None:
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for obj in result[1]:
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if key._compare_name_for_result(obj):
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break
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else:
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result = None
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if result is None:
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if raiseerr:
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raise exc.NoSuchColumnError(
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f"Could not locate column in row for column "
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f"{string_or_unprintable(key)!r}"
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)
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else:
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return None
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else:
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map[key] = result
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return result
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def _has_key(self, row, key):
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if key in self._keymap:
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return True
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else:
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return self._key_fallback(key, False) is not None
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class ResultProxy:
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"""Wraps a DB-API cursor object to provide easier access to row columns.
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Individual columns may be accessed by their integer position,
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case-insensitive column name, or by sqlalchemy schema.Column
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object. e.g.:
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row = fetchone()
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col1 = row[0] # access via integer position
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col2 = row['col2'] # access via name
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col3 = row[mytable.c.mycol] # access via Column object.
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ResultProxy also handles post-processing of result column
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data using sqlalchemy TypeEngine objects, which are referenced from
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the originating SQL statement that produced this result set.
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"""
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def __init__(self, connection, cursor, dialect, result_map=None):
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self._dialect = dialect
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self._result_map = result_map
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self._cursor = cursor
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self._connection = connection
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self._rowcount = cursor.rowcount
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self._metadata = None
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self._weak = None
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self._init_metadata()
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@property
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def dialect(self):
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"""SQLAlchemy dialect."""
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return self._dialect
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@property
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def cursor(self):
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return self._cursor
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def keys(self):
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"""Return the current set of string keys for rows."""
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if self._metadata:
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return tuple(self._metadata.keys)
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else:
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return ()
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@property
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def rowcount(self):
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"""Return the 'rowcount' for this result.
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The 'rowcount' reports the number of rows *matched*
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by the WHERE criterion of an UPDATE or DELETE statement.
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.. note::
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Notes regarding .rowcount:
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* This attribute returns the number of rows *matched*,
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which is not necessarily the same as the number of rows
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that were actually *modified* - an UPDATE statement, for example,
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may have no net change on a given row if the SET values
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given are the same as those present in the row already.
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Such a row would be matched but not modified.
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* .rowcount is *only* useful in conjunction
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with an UPDATE or DELETE statement. Contrary to what the Python
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DBAPI says, it does *not* return the
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number of rows available from the results of a SELECT statement
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as DBAPIs cannot support this functionality when rows are
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unbuffered.
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* Statements that use RETURNING may not return a correct
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rowcount.
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"""
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return self._rowcount
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def _init_metadata(self):
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cursor_description = self.cursor.description
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if cursor_description is not None:
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self._metadata = ResultMetaData(self, cursor_description)
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self._weak = weakref.ref(self, lambda _: self.close())
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else:
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self.close()
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@property
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def returns_rows(self):
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"""True if this ResultProxy returns rows.
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I.e. if it is legal to call the methods .fetchone(),
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.fetchmany() and .fetchall()`.
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"""
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return self._metadata is not None
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@property
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def closed(self):
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if self._cursor is None:
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return True
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return bool(self._cursor.closed)
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def close(self):
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"""Close this ResultProxy.
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Closes the underlying DBAPI cursor corresponding to the execution.
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Note that any data cached within this ResultProxy is still available.
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For some types of results, this may include buffered rows.
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If this ResultProxy was generated from an implicit execution,
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the underlying Connection will also be closed (returns the
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underlying DBAPI connection to the connection pool.)
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This method is called automatically when:
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* all result rows are exhausted using the fetchXXX() methods.
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* cursor.description is None.
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"""
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if self._cursor is None:
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return
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if not self._cursor.closed:
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self._cursor.close()
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self._cursor = None
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self._weak = None
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def __aiter__(self):
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return self
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async def __anext__(self):
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ret = await self.fetchone()
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if ret is not None:
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return ret
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raise StopAsyncIteration
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def _non_result(self):
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if self._metadata is None:
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raise exc.ResourceClosedError(
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"This result object does not return rows. "
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"It has been closed automatically."
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)
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else:
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raise exc.ResourceClosedError("This result object is closed.")
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def _process_rows(self, rows):
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process_row = RowProxy
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metadata = self._metadata
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keymap = metadata._keymap
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processors = metadata._processors
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return [process_row(metadata, row, processors, keymap) for row in rows]
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async def fetchall(self):
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"""Fetch all rows, just like DB-API cursor.fetchall()."""
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try:
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rows = await self.cursor.fetchall()
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except AttributeError:
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self._non_result()
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else:
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res = self._process_rows(rows)
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self.close()
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return res
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async def fetchone(self):
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"""Fetch one row, just like DB-API cursor.fetchone().
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If a row is present, the cursor remains open after this is called.
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Else the cursor is automatically closed and None is returned.
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"""
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try:
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row = await self.cursor.fetchone()
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except AttributeError:
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self._non_result()
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else:
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if row is not None:
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return self._process_rows([row])[0]
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else:
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self.close()
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return None
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async def fetchmany(self, size=None):
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"""Fetch many rows, just like DB-API
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cursor.fetchmany(size=cursor.arraysize).
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If rows are present, the cursor remains open after this is called.
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Else the cursor is automatically closed and an empty list is returned.
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"""
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try:
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if size is None:
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rows = await self.cursor.fetchmany()
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else:
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rows = await self.cursor.fetchmany(size)
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except AttributeError:
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self._non_result()
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else:
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res = self._process_rows(rows)
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if len(res) == 0:
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self.close()
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return res
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async def first(self):
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"""Fetch the first row and then close the result set unconditionally.
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Returns None if no row is present.
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"""
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if self._metadata is None:
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self._non_result()
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try:
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return await self.fetchone()
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finally:
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self.close()
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async def scalar(self):
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"""Fetch the first column of the first row, and close the result set.
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Returns None if no row is present.
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"""
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row = await self.first()
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if row is not None:
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return row[0]
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else:
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return None
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