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# engine/result.py
# Copyright (C) 2005-2016 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Define result set constructs including :class:`.ResultProxy`
and :class:`.RowProxy."""
from .. import exc, util
from ..sql import expression, sqltypes
import collections
import operator
# This reconstructor is necessary so that pickles with the C extension or
# without use the same Binary format.
try:
# We need a different reconstructor on the C extension so that we can
# add extra checks that fields have correctly been initialized by
# __setstate__.
from sqlalchemy.cresultproxy import safe_rowproxy_reconstructor
# The extra function embedding is needed so that the
# reconstructor function has the same signature whether or not
# the extension is present.
def rowproxy_reconstructor(cls, state):
return safe_rowproxy_reconstructor(cls, state)
except ImportError:
def rowproxy_reconstructor(cls, state):
obj = cls.__new__(cls)
obj.__setstate__(state)
return obj
try:
from sqlalchemy.cresultproxy import BaseRowProxy
except ImportError:
class BaseRowProxy(object):
__slots__ = ('_parent', '_row', '_processors', '_keymap')
def __init__(self, parent, row, processors, keymap):
"""RowProxy objects are constructed by ResultProxy objects."""
self._parent = parent
self._row = row
self._processors = processors
self._keymap = keymap
def __reduce__(self):
return (rowproxy_reconstructor,
(self.__class__, self.__getstate__()))
def values(self):
"""Return the values represented by this RowProxy as a list."""
return list(self)
def __iter__(self):
for processor, value in zip(self._processors, self._row):
if processor is None:
yield value
else:
yield processor(value)
def __len__(self):
return len(self._row)
def __getitem__(self, key):
try:
processor, obj, index = self._keymap[key]
except KeyError:
processor, obj, index = self._parent._key_fallback(key)
except TypeError:
if isinstance(key, slice):
l = []
for processor, value in zip(self._processors[key],
self._row[key]):
if processor is None:
l.append(value)
else:
l.append(processor(value))
return tuple(l)
else:
raise
if index is None:
raise exc.InvalidRequestError(
"Ambiguous column name '%s' in result set! "
"try 'use_labels' option on select statement." % key)
if processor is not None:
return processor(self._row[index])
else:
return self._row[index]
def __getattr__(self, name):
try:
return self[name]
except KeyError as e:
raise AttributeError(e.args[0])
class RowProxy(BaseRowProxy):
"""Proxy values from a single cursor row.
Mostly follows "ordered dictionary" behavior, mapping result
values to the string-based column name, the integer position of
the result in the row, as well as Column instances which can be
mapped to the original Columns that produced this result set (for
results that correspond to constructed SQL expressions).
"""
__slots__ = ()
def __contains__(self, key):
return self._parent._has_key(key)
def __getstate__(self):
return {
'_parent': self._parent,
'_row': tuple(self)
}
def __setstate__(self, state):
self._parent = parent = state['_parent']
self._row = state['_row']
self._processors = parent._processors
self._keymap = parent._keymap
__hash__ = None
def _op(self, other, op):
return op(tuple(self), tuple(other)) \
if isinstance(other, RowProxy) \
else op(tuple(self), other)
def __lt__(self, other):
return self._op(other, operator.lt)
def __le__(self, other):
return self._op(other, operator.le)
def __ge__(self, other):
return self._op(other, operator.ge)
def __gt__(self, other):
return self._op(other, operator.gt)
def __eq__(self, other):
return self._op(other, operator.eq)
def __ne__(self, other):
return self._op(other, operator.ne)
def __repr__(self):
return repr(tuple(self))
def has_key(self, key):
"""Return True if this RowProxy contains the given key."""
return self._parent._has_key(key)
def items(self):
"""Return a list of tuples, each tuple containing a key/value pair."""
# TODO: no coverage here
return [(key, self[key]) for key in self.keys()]
def keys(self):
"""Return the list of keys as strings represented by this RowProxy."""
return self._parent.keys
def iterkeys(self):
return iter(self._parent.keys)
def itervalues(self):
return iter(self)
try:
# Register RowProxy with Sequence,
# so sequence protocol is implemented
from collections import Sequence
Sequence.register(RowProxy)
except ImportError:
pass
class ResultMetaData(object):
"""Handle cursor.description, applying additional info from an execution
context."""
def __init__(self, parent, metadata):
context = parent.context
dialect = context.dialect
typemap = dialect.dbapi_type_map
translate_colname = context._translate_colname
self.case_sensitive = case_sensitive = dialect.case_sensitive
self._orig_processors = None
if context.result_column_struct:
result_columns, cols_are_ordered = context.result_column_struct
num_ctx_cols = len(result_columns)
else:
num_ctx_cols = None
if num_ctx_cols and \
cols_are_ordered and \
num_ctx_cols == len(metadata):
# case 1 - SQL expression statement, number of columns
# in result matches number of cols in compiled. This is the
# vast majority case for SQL expression constructs. In this
# case we don't bother trying to parse or match up to
# the colnames in the result description.
raw = [
(
idx,
key,
name.lower() if not case_sensitive else name,
context.get_result_processor(
type_, key, metadata[idx][1]
),
obj,
None
) for idx, (key, name, obj, type_)
in enumerate(result_columns)
]
self.keys = [
elem[0] for elem in result_columns
]
else:
# case 2 - raw string, or number of columns in result does
# not match number of cols in compiled. The raw string case
# is very common. The latter can happen
# when text() is used with only a partial typemap, or
# in the extremely unlikely cases where the compiled construct
# has a single element with multiple col expressions in it
# (e.g. has commas embedded) or there's some kind of statement
# that is adding extra columns.
# In all these cases we fall back to the "named" approach
# that SQLAlchemy has used up through 0.9.
if num_ctx_cols:
result_map = self._create_result_map(
result_columns, case_sensitive)
raw = []
self.keys = []
untranslated = None
for idx, rec in enumerate(metadata):
colname = rec[0]
coltype = rec[1]
if dialect.description_encoding:
colname = dialect._description_decoder(colname)
if translate_colname:
colname, untranslated = translate_colname(colname)
if dialect.requires_name_normalize:
colname = dialect.normalize_name(colname)
self.keys.append(colname)
if not case_sensitive:
colname = colname.lower()
if num_ctx_cols:
try:
ctx_rec = result_map[colname]
except KeyError:
mapped_type = typemap.get(coltype, sqltypes.NULLTYPE)
obj = None
else:
obj = ctx_rec[1]
mapped_type = ctx_rec[2]
else:
mapped_type = typemap.get(coltype, sqltypes.NULLTYPE)
obj = None
processor = context.get_result_processor(
mapped_type, colname, coltype)
raw.append(
(idx, colname, colname, processor, obj, untranslated)
)
# keymap indexes by integer index...
self._keymap = dict([
(elem[0], (elem[3], elem[4], elem[0]))
for elem in raw
])
# processors in key order for certain per-row
# views like __iter__ and slices
self._processors = [elem[3] for elem in raw]
if num_ctx_cols:
# keymap by primary string...
by_key = dict([
(elem[2], (elem[3], elem[4], elem[0]))
for elem in raw
])
# if by-primary-string dictionary smaller (or bigger?!) than
# number of columns, assume we have dupes, rewrite
# dupe records with "None" for index which results in
# ambiguous column exception when accessed.
if len(by_key) != num_ctx_cols:
seen = set()
for rec in raw:
key = rec[1]
if key in seen:
key = key.lower() if not self.case_sensitive else key
by_key[key] = (None, by_key[key][1], None)
seen.add(key)
# update keymap with secondary "object"-based keys
self._keymap.update([
(obj_elem, by_key[elem[2]])
for elem in raw if elem[4]
for obj_elem in elem[4]
])
# update keymap with primary string names taking
# precedence
self._keymap.update(by_key)
else:
self._keymap.update([
(elem[2], (elem[3], elem[4], elem[0]))
for elem in raw
])
# update keymap with "translated" names (sqlite-only thing)
if translate_colname:
self._keymap.update([
(elem[5], self._keymap[elem[2]])
for elem in raw if elem[5]
])
@classmethod
def _create_result_map(cls, result_columns, case_sensitive=True):
d = {}
for elem in result_columns:
key, rec = elem[0], elem[1:]
if not case_sensitive:
key = key.lower()
if key in d:
# conflicting keyname, just double up the list
# of objects. this will cause an "ambiguous name"
# error if an attempt is made by the result set to
# access.
e_name, e_obj, e_type = d[key]
d[key] = e_name, e_obj + rec[1], e_type
else:
d[key] = rec
return d
@util.pending_deprecation("0.8", "sqlite dialect uses "
"_translate_colname() now")
def _set_keymap_synonym(self, name, origname):
"""Set a synonym for the given name.
Some dialects (SQLite at the moment) may use this to
adjust the column names that are significant within a
row.
"""
rec = (processor, obj, i) = self._keymap[origname if
self.case_sensitive
else origname.lower()]
if self._keymap.setdefault(name, rec) is not rec:
self._keymap[name] = (processor, obj, None)
def _key_fallback(self, key, raiseerr=True):
map = self._keymap
result = None
if isinstance(key, util.string_types):
result = map.get(key if self.case_sensitive else key.lower())
# fallback for targeting a ColumnElement to a textual expression
# this is a rare use case which only occurs when matching text()
# or colummn('name') constructs to ColumnElements, or after a
# pickle/unpickle roundtrip
elif isinstance(key, expression.ColumnElement):
if key._label and (
key._label
if self.case_sensitive
else key._label.lower()) in map:
result = map[key._label
if self.case_sensitive
else key._label.lower()]
elif hasattr(key, 'name') and (
key.name
if self.case_sensitive
else key.name.lower()) in map:
# match is only on name.
result = map[key.name
if self.case_sensitive
else key.name.lower()]
# search extra hard to make sure this
# isn't a column/label name overlap.
# this check isn't currently available if the row
# was unpickled.
if result is not None and \
result[1] is not None:
for obj in result[1]:
if key._compare_name_for_result(obj):
break
else:
result = None
if result is None:
if raiseerr:
raise exc.NoSuchColumnError(
"Could not locate column in row for column '%s'" %
expression._string_or_unprintable(key))
else:
return None
else:
map[key] = result
return result
def _has_key(self, key):
if key in self._keymap:
return True
else:
return self._key_fallback(key, False) is not None
def _getter(self, key, raiseerr=True):
if key in self._keymap:
processor, obj, index = self._keymap[key]
else:
ret = self._key_fallback(key, raiseerr)
if ret is None:
return None
processor, obj, index = ret
if index is None:
raise exc.InvalidRequestError(
"Ambiguous column name '%s' in result set! "
"try 'use_labels' option on select statement." % key)
return operator.itemgetter(index)
def __getstate__(self):
return {
'_pickled_keymap': dict(
(key, index)
for key, (processor, obj, index) in self._keymap.items()
if isinstance(key, util.string_types + util.int_types)
),
'keys': self.keys,
"case_sensitive": self.case_sensitive,
}
def __setstate__(self, state):
# the row has been processed at pickling time so we don't need any
# processor anymore
self._processors = [None for _ in range(len(state['keys']))]
self._keymap = keymap = {}
for key, index in state['_pickled_keymap'].items():
# not preserving "obj" here, unfortunately our
# proxy comparison fails with the unpickle
keymap[key] = (None, None, index)
self.keys = state['keys']
self.case_sensitive = state['case_sensitive']
self._echo = False
class ResultProxy(object):
"""Wraps a DB-API cursor object to provide easier access to row columns.
Individual columns may be accessed by their integer position,
case-insensitive column name, or by ``schema.Column``
object. e.g.::
row = fetchone()
col1 = row[0] # access via integer position
col2 = row['col2'] # access via name
col3 = row[mytable.c.mycol] # access via Column object.
``ResultProxy`` also handles post-processing of result column
data using ``TypeEngine`` objects, which are referenced from
the originating SQL statement that produced this result set.
"""
_process_row = RowProxy
out_parameters = None
_can_close_connection = False
_metadata = None
_soft_closed = False
closed = False
def __init__(self, context):
self.context = context
self.dialect = context.dialect
self.cursor = self._saved_cursor = context.cursor
self.connection = context.root_connection
self._echo = self.connection._echo and \
context.engine._should_log_debug()
self._init_metadata()
def _getter(self, key, raiseerr=True):
try:
getter = self._metadata._getter
except AttributeError:
return self._non_result(None)
else:
return getter(key, raiseerr)
def _has_key(self, key):
try:
has_key = self._metadata._has_key
except AttributeError:
return self._non_result(None)
else:
return has_key(key)
def _init_metadata(self):
metadata = self._cursor_description()
if metadata is not None:
if self.context.compiled and \
'compiled_cache' in self.context.execution_options:
if self.context.compiled._cached_metadata:
self._metadata = self.context.compiled._cached_metadata
else:
self._metadata = self.context.compiled._cached_metadata = \
ResultMetaData(self, metadata)
else:
self._metadata = ResultMetaData(self, metadata)
if self._echo:
self.context.engine.logger.debug(
"Col %r", tuple(x[0] for x in metadata))
def keys(self):
"""Return the current set of string keys for rows."""
if self._metadata:
return self._metadata.keys
else:
return []
@util.memoized_property
def rowcount(self):
"""Return the 'rowcount' for this result.
The 'rowcount' reports the number of rows *matched*
by the WHERE criterion of an UPDATE or DELETE statement.
.. note::
Notes regarding :attr:`.ResultProxy.rowcount`:
* This attribute returns the number of rows *matched*,
which is not necessarily the same as the number of rows
that were actually *modified* - an UPDATE statement, for example,
may have no net change on a given row if the SET values
given are the same as those present in the row already.
Such a row would be matched but not modified.
On backends that feature both styles, such as MySQL,
rowcount is configured by default to return the match
count in all cases.
* :attr:`.ResultProxy.rowcount` is *only* useful in conjunction
with an UPDATE or DELETE statement. Contrary to what the Python
DBAPI says, it does *not* return the
number of rows available from the results of a SELECT statement
as DBAPIs cannot support this functionality when rows are
unbuffered.
* :attr:`.ResultProxy.rowcount` may not be fully implemented by
all dialects. In particular, most DBAPIs do not support an
aggregate rowcount result from an executemany call.
The :meth:`.ResultProxy.supports_sane_rowcount` and
:meth:`.ResultProxy.supports_sane_multi_rowcount` methods
will report from the dialect if each usage is known to be
supported.
* Statements that use RETURNING may not return a correct
rowcount.
"""
try:
return self.context.rowcount
except Exception as e:
self.connection._handle_dbapi_exception(
e, None, None, self.cursor, self.context)
@property
def lastrowid(self):
"""return the 'lastrowid' accessor on the DBAPI cursor.
This is a DBAPI specific method and is only functional
for those backends which support it, for statements
where it is appropriate. It's behavior is not
consistent across backends.
Usage of this method is normally unnecessary when
using insert() expression constructs; the
:attr:`~ResultProxy.inserted_primary_key` attribute provides a
tuple of primary key values for a newly inserted row,
regardless of database backend.
"""
try:
return self._saved_cursor.lastrowid
except Exception as e:
self.connection._handle_dbapi_exception(
e, None, None,
self._saved_cursor, self.context)
@property
def returns_rows(self):
"""True if this :class:`.ResultProxy` returns rows.
I.e. if it is legal to call the methods
:meth:`~.ResultProxy.fetchone`,
:meth:`~.ResultProxy.fetchmany`
:meth:`~.ResultProxy.fetchall`.
"""
return self._metadata is not None
@property
def is_insert(self):
"""True if this :class:`.ResultProxy` is the result
of a executing an expression language compiled
:func:`.expression.insert` construct.
When True, this implies that the
:attr:`inserted_primary_key` attribute is accessible,
assuming the statement did not include
a user defined "returning" construct.
"""
return self.context.isinsert
def _cursor_description(self):
"""May be overridden by subclasses."""
return self._saved_cursor.description
def _soft_close(self, _autoclose_connection=True):
"""Soft close this :class:`.ResultProxy`.
This releases all DBAPI cursor resources, but leaves the
ResultProxy "open" from a semantic perspective, meaning the
fetchXXX() methods will continue to return empty results.
This method is called automatically when:
* all result rows are exhausted using the fetchXXX() methods.
* cursor.description is None.
This method is **not public**, but is documented in order to clarify
the "autoclose" process used.
.. versionadded:: 1.0.0
.. seealso::
:meth:`.ResultProxy.close`
"""
if self._soft_closed:
return
self._soft_closed = True
cursor = self.cursor
self.connection._safe_close_cursor(cursor)
if _autoclose_connection and \
self.connection.should_close_with_result:
self.connection.close()
self.cursor = None
def close(self):
"""Close this ResultProxy.
This closes out the underlying DBAPI cursor corresonding
to the statement execution, if one is still present. Note that the
DBAPI cursor is automatically released when the :class:`.ResultProxy`
exhausts all available rows. :meth:`.ResultProxy.close` is generally
an optional method except in the case when discarding a
:class:`.ResultProxy` that still has additional rows pending for fetch.
In the case of a result that is the product of
:ref:`connectionless execution <dbengine_implicit>`,
the underyling :class:`.Connection` object is also closed, which
:term:`releases` DBAPI connection resources.
After this method is called, it is no longer valid to call upon
the fetch methods, which will raise a :class:`.ResourceClosedError`
on subsequent use.
.. versionchanged:: 1.0.0 - the :meth:`.ResultProxy.close` method
has been separated out from the process that releases the underlying
DBAPI cursor resource. The "auto close" feature of the
:class:`.Connection` now performs a so-called "soft close", which
releases the underlying DBAPI cursor, but allows the
:class:`.ResultProxy` to still behave as an open-but-exhausted
result set; the actual :meth:`.ResultProxy.close` method is never
called. It is still safe to discard a :class:`.ResultProxy`
that has been fully exhausted without calling this method.
.. seealso::
:ref:`connections_toplevel`
:meth:`.ResultProxy._soft_close`
"""
if not self.closed:
self._soft_close()
self.closed = True
def __iter__(self):
while True:
row = self.fetchone()
if row is None:
return
else:
yield row
@util.memoized_property
def inserted_primary_key(self):
"""Return the primary key for the row just inserted.
The return value is a list of scalar values
corresponding to the list of primary key columns
in the target table.
This only applies to single row :func:`.insert`
constructs which did not explicitly specify
:meth:`.Insert.returning`.
Note that primary key columns which specify a
server_default clause,
or otherwise do not qualify as "autoincrement"
columns (see the notes at :class:`.Column`), and were
generated using the database-side default, will
appear in this list as ``None`` unless the backend
supports "returning" and the insert statement executed
with the "implicit returning" enabled.
Raises :class:`~sqlalchemy.exc.InvalidRequestError` if the executed
statement is not a compiled expression construct
or is not an insert() construct.
"""
if not self.context.compiled:
raise exc.InvalidRequestError(
"Statement is not a compiled "
"expression construct.")
elif not self.context.isinsert:
raise exc.InvalidRequestError(
"Statement is not an insert() "
"expression construct.")
elif self.context._is_explicit_returning:
raise exc.InvalidRequestError(
"Can't call inserted_primary_key "
"when returning() "
"is used.")
return self.context.inserted_primary_key
def last_updated_params(self):
"""Return the collection of updated parameters from this
execution.
Raises :class:`~sqlalchemy.exc.InvalidRequestError` if the executed
statement is not a compiled expression construct
or is not an update() construct.
"""
if not self.context.compiled:
raise exc.InvalidRequestError(
"Statement is not a compiled "
"expression construct.")
elif not self.context.isupdate:
raise exc.InvalidRequestError(
"Statement is not an update() "
"expression construct.")
elif self.context.executemany:
return self.context.compiled_parameters
else:
return self.context.compiled_parameters[0]
def last_inserted_params(self):
"""Return the collection of inserted parameters from this
execution.
Raises :class:`~sqlalchemy.exc.InvalidRequestError` if the executed
statement is not a compiled expression construct
or is not an insert() construct.
"""
if not self.context.compiled:
raise exc.InvalidRequestError(
"Statement is not a compiled "
"expression construct.")
elif not self.context.isinsert:
raise exc.InvalidRequestError(
"Statement is not an insert() "
"expression construct.")
elif self.context.executemany:
return self.context.compiled_parameters
else:
return self.context.compiled_parameters[0]
@property
def returned_defaults(self):
"""Return the values of default columns that were fetched using
the :meth:`.ValuesBase.return_defaults` feature.
The value is an instance of :class:`.RowProxy`, or ``None``
if :meth:`.ValuesBase.return_defaults` was not used or if the
backend does not support RETURNING.
.. versionadded:: 0.9.0
.. seealso::
:meth:`.ValuesBase.return_defaults`
"""
return self.context.returned_defaults
def lastrow_has_defaults(self):
"""Return ``lastrow_has_defaults()`` from the underlying
:class:`.ExecutionContext`.
See :class:`.ExecutionContext` for details.
"""
return self.context.lastrow_has_defaults()
def postfetch_cols(self):
"""Return ``postfetch_cols()`` from the underlying
:class:`.ExecutionContext`.
See :class:`.ExecutionContext` for details.
Raises :class:`~sqlalchemy.exc.InvalidRequestError` if the executed
statement is not a compiled expression construct
or is not an insert() or update() construct.
"""
if not self.context.compiled:
raise exc.InvalidRequestError(
"Statement is not a compiled "
"expression construct.")
elif not self.context.isinsert and not self.context.isupdate:
raise exc.InvalidRequestError(
"Statement is not an insert() or update() "
"expression construct.")
return self.context.postfetch_cols
def prefetch_cols(self):
"""Return ``prefetch_cols()`` from the underlying
:class:`.ExecutionContext`.
See :class:`.ExecutionContext` for details.
Raises :class:`~sqlalchemy.exc.InvalidRequestError` if the executed
statement is not a compiled expression construct
or is not an insert() or update() construct.
"""
if not self.context.compiled:
raise exc.InvalidRequestError(
"Statement is not a compiled "
"expression construct.")
elif not self.context.isinsert and not self.context.isupdate:
raise exc.InvalidRequestError(
"Statement is not an insert() or update() "
"expression construct.")
return self.context.prefetch_cols
def supports_sane_rowcount(self):
"""Return ``supports_sane_rowcount`` from the dialect.
See :attr:`.ResultProxy.rowcount` for background.
"""
return self.dialect.supports_sane_rowcount
def supports_sane_multi_rowcount(self):
"""Return ``supports_sane_multi_rowcount`` from the dialect.
See :attr:`.ResultProxy.rowcount` for background.
"""
return self.dialect.supports_sane_multi_rowcount
def _fetchone_impl(self):
try:
return self.cursor.fetchone()
except AttributeError:
return self._non_result(None)
def _fetchmany_impl(self, size=None):
try:
if size is None:
return self.cursor.fetchmany()
else:
return self.cursor.fetchmany(size)
except AttributeError:
return self._non_result([])
def _fetchall_impl(self):
try:
return self.cursor.fetchall()
except AttributeError:
return self._non_result([])
def _non_result(self, default):
if self._metadata is None:
raise exc.ResourceClosedError(
"This result object does not return rows. "
"It has been closed automatically.",
)
elif self.closed:
raise exc.ResourceClosedError("This result object is closed.")
else:
return default
def process_rows(self, rows):
process_row = self._process_row
metadata = self._metadata
keymap = metadata._keymap
processors = metadata._processors
if self._echo:
log = self.context.engine.logger.debug
l = []
for row in rows:
log("Row %r", row)
l.append(process_row(metadata, row, processors, keymap))
return l
else:
return [process_row(metadata, row, processors, keymap)
for row in rows]
def fetchall(self):
"""Fetch all rows, just like DB-API ``cursor.fetchall()``.
After all rows have been exhausted, the underlying DBAPI
cursor resource is released, and the object may be safely
discarded.
Subsequent calls to :meth:`.ResultProxy.fetchall` will return
an empty list. After the :meth:`.ResultProxy.close` method is
called, the method will raise :class:`.ResourceClosedError`.
.. versionchanged:: 1.0.0 - Added "soft close" behavior which
allows the result to be used in an "exhausted" state prior to
calling the :meth:`.ResultProxy.close` method.
"""
try:
l = self.process_rows(self._fetchall_impl())
self._soft_close()
return l
except Exception as e:
self.connection._handle_dbapi_exception(
e, None, None,
self.cursor, self.context)
def fetchmany(self, size=None):
"""Fetch many rows, just like DB-API
``cursor.fetchmany(size=cursor.arraysize)``.
After all rows have been exhausted, the underlying DBAPI
cursor resource is released, and the object may be safely
discarded.
Calls to :meth:`.ResultProxy.fetchmany` after all rows have been
exhuasted will return
an empty list. After the :meth:`.ResultProxy.close` method is
called, the method will raise :class:`.ResourceClosedError`.
.. versionchanged:: 1.0.0 - Added "soft close" behavior which
allows the result to be used in an "exhausted" state prior to
calling the :meth:`.ResultProxy.close` method.
"""
try:
l = self.process_rows(self._fetchmany_impl(size))
if len(l) == 0:
self._soft_close()
return l
except Exception as e:
self.connection._handle_dbapi_exception(
e, None, None,
self.cursor, self.context)
def fetchone(self):
"""Fetch one row, just like DB-API ``cursor.fetchone()``.
After all rows have been exhausted, the underlying DBAPI
cursor resource is released, and the object may be safely
discarded.
Calls to :meth:`.ResultProxy.fetchone` after all rows have
been exhausted will return ``None``.
After the :meth:`.ResultProxy.close` method is
called, the method will raise :class:`.ResourceClosedError`.
.. versionchanged:: 1.0.0 - Added "soft close" behavior which
allows the result to be used in an "exhausted" state prior to
calling the :meth:`.ResultProxy.close` method.
"""
try:
row = self._fetchone_impl()
if row is not None:
return self.process_rows([row])[0]
else:
self._soft_close()
return None
except Exception as e:
self.connection._handle_dbapi_exception(
e, None, None,
self.cursor, self.context)
def first(self):
"""Fetch the first row and then close the result set unconditionally.
Returns None if no row is present.
After calling this method, the object is fully closed,
e.g. the :meth:`.ResultProxy.close` method will have been called.
"""
if self._metadata is None:
return self._non_result(None)
try:
row = self._fetchone_impl()
except Exception as e:
self.connection._handle_dbapi_exception(
e, None, None,
self.cursor, self.context)
try:
if row is not None:
return self.process_rows([row])[0]
else:
return None
finally:
self.close()
def scalar(self):
"""Fetch the first column of the first row, and close the result set.
Returns None if no row is present.
After calling this method, the object is fully closed,
e.g. the :meth:`.ResultProxy.close` method will have been called.
"""
row = self.first()
if row is not None:
return row[0]
else:
return None
class BufferedRowResultProxy(ResultProxy):
"""A ResultProxy with row buffering behavior.
``ResultProxy`` that buffers the contents of a selection of rows
before ``fetchone()`` is called. This is to allow the results of
``cursor.description`` to be available immediately, when
interfacing with a DB-API that requires rows to be consumed before
this information is available (currently psycopg2, when used with
server-side cursors).
The pre-fetching behavior fetches only one row initially, and then
grows its buffer size by a fixed amount with each successive need
for additional rows up to a size of 1000.
The size argument is configurable using the ``max_row_buffer``
execution option::
with psycopg2_engine.connect() as conn:
result = conn.execution_options(
stream_results=True, max_row_buffer=50
).execute("select * from table")
.. versionadded:: 1.0.6 Added the ``max_row_buffer`` option.
.. seealso::
:ref:`psycopg2_execution_options`
"""
def _init_metadata(self):
self._max_row_buffer = self.context.execution_options.get(
'max_row_buffer', None)
self.__buffer_rows()
super(BufferedRowResultProxy, self)._init_metadata()
# this is a "growth chart" for the buffering of rows.
# each successive __buffer_rows call will use the next
# value in the list for the buffer size until the max
# is reached
size_growth = {
1: 5,
5: 10,
10: 20,
20: 50,
50: 100,
100: 250,
250: 500,
500: 1000
}
def __buffer_rows(self):
if self.cursor is None:
return
size = getattr(self, '_bufsize', 1)
self.__rowbuffer = collections.deque(self.cursor.fetchmany(size))
self._bufsize = self.size_growth.get(size, size)
if self._max_row_buffer is not None:
self._bufsize = min(self._max_row_buffer, self._bufsize)
def _soft_close(self, **kw):
self.__rowbuffer.clear()
super(BufferedRowResultProxy, self)._soft_close(**kw)
def _fetchone_impl(self):
if self.cursor is None:
return self._non_result(None)
if not self.__rowbuffer:
self.__buffer_rows()
if not self.__rowbuffer:
return None
return self.__rowbuffer.popleft()
def _fetchmany_impl(self, size=None):
if size is None:
return self._fetchall_impl()
result = []
for x in range(0, size):
row = self._fetchone_impl()
if row is None:
break
result.append(row)
return result
def _fetchall_impl(self):
if self.cursor is None:
return self._non_result([])
self.__rowbuffer.extend(self.cursor.fetchall())
ret = self.__rowbuffer
self.__rowbuffer = collections.deque()
return ret
class FullyBufferedResultProxy(ResultProxy):
"""A result proxy that buffers rows fully upon creation.
Used for operations where a result is to be delivered
after the database conversation can not be continued,
such as MSSQL INSERT...OUTPUT after an autocommit.
"""
def _init_metadata(self):
super(FullyBufferedResultProxy, self)._init_metadata()
self.__rowbuffer = self._buffer_rows()
def _buffer_rows(self):
return collections.deque(self.cursor.fetchall())
def _soft_close(self, **kw):
self.__rowbuffer.clear()
super(FullyBufferedResultProxy, self)._soft_close(**kw)
def _fetchone_impl(self):
if self.__rowbuffer:
return self.__rowbuffer.popleft()
else:
return self._non_result(None)
def _fetchmany_impl(self, size=None):
if size is None:
return self._fetchall_impl()
result = []
for x in range(0, size):
row = self._fetchone_impl()
if row is None:
break
result.append(row)
return result
def _fetchall_impl(self):
if not self.cursor:
return self._non_result([])
ret = self.__rowbuffer
self.__rowbuffer = collections.deque()
return ret
class BufferedColumnRow(RowProxy):
def __init__(self, parent, row, processors, keymap):
# preprocess row
row = list(row)
# this is a tad faster than using enumerate
index = 0
for processor in parent._orig_processors:
if processor is not None:
row[index] = processor(row[index])
index += 1
row = tuple(row)
super(BufferedColumnRow, self).__init__(parent, row,
processors, keymap)
class BufferedColumnResultProxy(ResultProxy):
"""A ResultProxy with column buffering behavior.
``ResultProxy`` that loads all columns into memory each time
fetchone() is called. If fetchmany() or fetchall() are called,
the full grid of results is fetched. This is to operate with
databases where result rows contain "live" results that fall out
of scope unless explicitly fetched. Currently this includes
cx_Oracle LOB objects.
"""
_process_row = BufferedColumnRow
def _init_metadata(self):
super(BufferedColumnResultProxy, self)._init_metadata()
metadata = self._metadata
# don't double-replace the processors, in the case
# of a cached ResultMetaData
if metadata._orig_processors is None:
# orig_processors will be used to preprocess each row when
# they are constructed.
metadata._orig_processors = metadata._processors
# replace the all type processors by None processors.
metadata._processors = [None for _ in range(len(metadata.keys))]
keymap = {}
for k, (func, obj, index) in metadata._keymap.items():
keymap[k] = (None, obj, index)
metadata._keymap = keymap
def fetchall(self):
# can't call cursor.fetchall(), since rows must be
# fully processed before requesting more from the DBAPI.
l = []
while True:
row = self.fetchone()
if row is None:
break
l.append(row)
return l
def fetchmany(self, size=None):
# can't call cursor.fetchmany(), since rows must be
# fully processed before requesting more from the DBAPI.
if size is None:
return self.fetchall()
l = []
for i in range(size):
row = self.fetchone()
if row is None:
break
l.append(row)
return l
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