# sql/util.py
# Copyright (C) 2005-2013 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
from .. import exc, schema, util, sql
from ..util import topological
from . import expression, operators, visitors
from itertools import chain
from collections import deque
"""Utility functions that build upon SQL and Schema constructs."""
def sort_tables(tables, skip_fn=None, extra_dependencies=None):
"""sort a collection of Table objects in order of
their foreign-key dependency."""
tables = list(tables)
tuples = []
if extra_dependencies is not None:
tuples.extend(extra_dependencies)
def visit_foreign_key(fkey):
if fkey.use_alter:
return
elif skip_fn and skip_fn(fkey):
return
parent_table = fkey.column.table
if parent_table in tables:
child_table = fkey.parent.table
if parent_table is not child_table:
tuples.append((parent_table, child_table))
for table in tables:
visitors.traverse(table,
{'schema_visitor': True},
{'foreign_key': visit_foreign_key})
tuples.extend(
[parent, table] for parent in table._extra_dependencies
)
return list(topological.sort(tuples, tables))
def find_join_source(clauses, join_to):
"""Given a list of FROM clauses and a selectable,
return the first index and element from the list of
clauses which can be joined against the selectable. returns
None, None if no match is found.
e.g.::
clause1 = table1.join(table2)
clause2 = table4.join(table5)
join_to = table2.join(table3)
find_join_source([clause1, clause2], join_to) == clause1
"""
selectables = list(expression._from_objects(join_to))
for i, f in enumerate(clauses):
for s in selectables:
if f.is_derived_from(s):
return i, f
else:
return None, None
def visit_binary_product(fn, expr):
"""Produce a traversal of the given expression, delivering
column comparisons to the given function.
The function is of the form::
def my_fn(binary, left, right)
For each binary expression located which has a
comparison operator, the product of "left" and
"right" will be delivered to that function,
in terms of that binary.
Hence an expression like::
and_(
(a + b) == q + func.sum(e + f),
j == r
)
would have the traversal::
a <eq> q
a <eq> e
a <eq> f
b <eq> q
b <eq> e
b <eq> f
j <eq> r
That is, every combination of "left" and
"right" that doesn't further contain
a binary comparison is passed as pairs.
"""
stack = []
def visit(element):
if isinstance(element, (expression.ScalarSelect)):
# we dont want to dig into correlated subqueries,
# those are just column elements by themselves
yield element
elif element.__visit_name__ == 'binary' and \
operators.is_comparison(element.operator):
stack.insert(0, element)
for l in visit(element.left):
for r in visit(element.right):
fn(stack[0], l, r)
stack.pop(0)
for elem in element.get_children():
visit(elem)
else:
if isinstance(element, expression.ColumnClause):
yield element
for elem in element.get_children():
for e in visit(elem):
yield e
list(visit(expr))
def find_tables(clause, check_columns=False,
include_aliases=False, include_joins=False,
include_selects=False, include_crud=False):
"""locate Table objects within the given expression."""
tables = []
_visitors = {}
if include_selects:
_visitors['select'] = _visitors['compound_select'] = tables.append
if include_joins:
_visitors['join'] = tables.append
if include_aliases:
_visitors['alias'] = tables.append
if include_crud:
_visitors['insert'] = _visitors['update'] = \
_visitors['delete'] = lambda ent: tables.append(ent.table)
if check_columns:
def visit_column(column):
tables.append(column.table)
_visitors['column'] = visit_column
_visitors['table'] = tables.append
visitors.traverse(clause, {'column_collections': False}, _visitors)
return tables
def find_columns(clause):
"""locate Column objects within the given expression."""
cols = util.column_set()
visitors.traverse(clause, {}, {'column': cols.add})
return cols
def unwrap_order_by(clause):
"""Break up an 'order by' expression into individual column-expressions,
without DESC/ASC/NULLS FIRST/NULLS LAST"""
cols = util.column_set()
stack = deque([clause])
while stack:
t = stack.popleft()
if isinstance(t, expression.ColumnElement) and \
(
not isinstance(t, expression.UnaryExpression) or \
not operators.is_ordering_modifier(t.modifier)
):
cols.add(t)
else:
for c in t.get_children():
stack.append(c)
return cols
def clause_is_present(clause, search):
"""Given a target clause and a second to search within, return True
if the target is plainly present in the search without any
subqueries or aliases involved.
Basically descends through Joins.
"""
stack = [search]
while stack:
elem = stack.pop()
if clause == elem: # use == here so that Annotated's compare
return True
elif isinstance(elem, expression.Join):
stack.extend((elem.left, elem.right))
return False
def bind_values(clause):
"""Return an ordered list of "bound" values in the given clause.
E.g.::
>>> expr = and_(
... table.c.foo==5, table.c.foo==7
... )
>>> bind_values(expr)
[5, 7]
"""
v = []
def visit_bindparam(bind):
v.append(bind.effective_value)
visitors.traverse(clause, {}, {'bindparam': visit_bindparam})
return v
def _quote_ddl_expr(element):
if isinstance(element, basestring):
element = element.replace("'", "''")
return "'%s'" % element
else:
return repr(element)
class _repr_params(object):
"""A string view of bound parameters, truncating
display to the given number of 'multi' parameter sets.
"""
def __init__(self, params, batches):
self.params = params
self.batches = batches
def __repr__(self):
if isinstance(self.params, (list, tuple)) and \
len(self.params) > self.batches and \
isinstance(self.params[0], (list, dict, tuple)):
msg = " ... displaying %i of %i total bound parameter sets ... "
return ' '.join((
repr(self.params[:self.batches - 2])[0:-1],
msg % (self.batches, len(self.params)),
repr(self.params[-2:])[1:]
))
else:
return repr(self.params)
def expression_as_ddl(clause):
"""Given a SQL expression, convert for usage in DDL, such as
CREATE INDEX and CHECK CONSTRAINT.
Converts bind params into quoted literals, column identifiers
into detached column constructs so that the parent table
identifier is not included.
.. deprecated:: this function is removed in 0.9.0.
"""
def repl(element):
if isinstance(element, expression.BindParameter):
return expression.literal_column(_quote_ddl_expr(element.value))
elif isinstance(element, expression.ColumnClause) and \
element.table is not None:
col = expression.column(element.name)
col.quote = element.quote
return col
else:
return None
return visitors.replacement_traverse(clause, {}, repl)
def adapt_criterion_to_null(crit, nulls):
"""given criterion containing bind params, convert selected elements
to IS NULL.
"""
def visit_binary(binary):
if isinstance(binary.left, expression.BindParameter) \
and binary.left._identifying_key in nulls:
# reverse order if the NULL is on the left side
binary.left = binary.right
binary.right = expression.null()
binary.operator = operators.is_
binary.negate = operators.isnot
elif isinstance(binary.right, expression.BindParameter) \
and binary.right._identifying_key in nulls:
binary.right = expression.null()
binary.operator = operators.is_
binary.negate = operators.isnot
return visitors.cloned_traverse(crit, {}, {'binary': visit_binary})
def join_condition(a, b, ignore_nonexistent_tables=False,
a_subset=None,
consider_as_foreign_keys=None):
"""create a join condition between two tables or selectables.
e.g.::
join_condition(tablea, tableb)
would produce an expression along the lines of::
tablea.c.id==tableb.c.tablea_id
The join is determined based on the foreign key relationships
between the two selectables. If there are multiple ways
to join, or no way to join, an error is raised.
:param ignore_nonexistent_tables: Deprecated - this
flag is no longer used. Only resolution errors regarding
the two given tables are propagated.
:param a_subset: An optional expression that is a sub-component
of ``a``. An attempt will be made to join to just this sub-component
first before looking at the full ``a`` construct, and if found
will be successful even if there are other ways to join to ``a``.
This allows the "right side" of a join to be passed thereby
providing a "natural join".
"""
crit = []
constraints = set()
for left in (a_subset, a):
if left is None:
continue
for fk in sorted(
b.foreign_keys,
key=lambda fk: fk.parent._creation_order):
if consider_as_foreign_keys is not None and \
fk.parent not in consider_as_foreign_keys:
continue
try:
col = fk.get_referent(left)
except exc.NoReferenceError, nrte:
if nrte.table_name == left.name:
raise
else:
continue
if col is not None:
crit.append(col == fk.parent)
constraints.add(fk.constraint)
if left is not b:
for fk in sorted(
left.foreign_keys,
key=lambda fk: fk.parent._creation_order):
if consider_as_foreign_keys is not None and \
fk.parent not in consider_as_foreign_keys:
continue
try:
col = fk.get_referent(b)
except exc.NoReferenceError, nrte:
if nrte.table_name == b.name:
raise
else:
# this is totally covered. can't get
# coverage to mark it.
continue
if col is not None:
crit.append(col == fk.parent)
constraints.add(fk.constraint)
if crit:
break
if len(crit) == 0:
if isinstance(b, expression.FromGrouping):
hint = " Perhaps you meant to convert the right side to a "\
"subquery using alias()?"
else:
hint = ""
raise exc.NoForeignKeysError(
"Can't find any foreign key relationships "
"between '%s' and '%s'.%s" % (a.description, b.description, hint))
elif len(constraints) > 1:
raise exc.AmbiguousForeignKeysError(
"Can't determine join between '%s' and '%s'; "
"tables have more than one foreign key "
"constraint relationship between them. "
"Please specify the 'onclause' of this "
"join explicitly." % (a.description, b.description))
elif len(crit) == 1:
return (crit[0])
else:
return sql.and_(*crit)
class Annotated(object):
"""clones a ClauseElement and applies an 'annotations' dictionary.
Unlike regular clones, this clone also mimics __hash__() and
__cmp__() of the original element so that it takes its place
in hashed collections.
A reference to the original element is maintained, for the important
reason of keeping its hash value current. When GC'ed, the
hash value may be reused, causing conflicts.
"""
def __new__(cls, *args):
if not args:
# clone constructor
return object.__new__(cls)
else:
element, values = args
# pull appropriate subclass from registry of annotated
# classes
try:
cls = annotated_classes[element.__class__]
except KeyError:
cls = annotated_classes[element.__class__] = type.__new__(type,
"Annotated%s" % element.__class__.__name__,
(cls, element.__class__), {})
return object.__new__(cls)
def __init__(self, element, values):
# force FromClause to generate their internal
# collections into __dict__
if isinstance(element, expression.FromClause):
element.c
self.__dict__ = element.__dict__.copy()
expression.ColumnElement.comparator._reset(self)
self.__element = element
self._annotations = values
def _annotate(self, values):
_values = self._annotations.copy()
_values.update(values)
return self._with_annotations(_values)
def _with_annotations(self, values):
clone = self.__class__.__new__(self.__class__)
clone.__dict__ = self.__dict__.copy()
expression.ColumnElement.comparator._reset(clone)
clone._annotations = values
return clone
def _deannotate(self, values=None, clone=True):
if values is None:
return self.__element
else:
_values = self._annotations.copy()
for v in values:
_values.pop(v, None)
return self._with_annotations(_values)
def _compiler_dispatch(self, visitor, **kw):
return self.__element.__class__._compiler_dispatch(self, visitor, **kw)
@property
def _constructor(self):
return self.__element._constructor
def _clone(self):
clone = self.__element._clone()
if clone is self.__element:
# detect immutable, don't change anything
return self
else:
# update the clone with any changes that have occurred
# to this object's __dict__.
clone.__dict__.update(self.__dict__)
return self.__class__(clone, self._annotations)
def __hash__(self):
return hash(self.__element)
def __eq__(self, other):
if isinstance(self.__element, expression.ColumnOperators):
return self.__element.__class__.__eq__(self, other)
else:
return hash(other) == hash(self)
class AnnotatedColumnElement(Annotated):
def __init__(self, element, values):
Annotated.__init__(self, element, values)
for attr in ('name', 'key', 'table'):
if self.__dict__.get(attr, False) is None:
self.__dict__.pop(attr)
@util.memoized_property
def name(self):
"""pull 'name' from parent, if not present"""
return self._Annotated__element.name
@util.memoized_property
def table(self):
"""pull 'table' from parent, if not present"""
return self._Annotated__element.table
@util.memoized_property
def key(self):
"""pull 'key' from parent, if not present"""
return self._Annotated__element.key
@util.memoized_property
def info(self):
return self._Annotated__element.info
# hard-generate Annotated subclasses. this technique
# is used instead of on-the-fly types (i.e. type.__new__())
# so that the resulting objects are pickleable.
annotated_classes = {}
for cls in expression.__dict__.values() + [schema.Column, schema.Table]:
if isinstance(cls, type) and issubclass(cls, expression.ClauseElement):
if issubclass(cls, expression.ColumnElement):
annotation_cls = "AnnotatedColumnElement"
else:
annotation_cls = "Annotated"
exec "class Annotated%s(%s, cls):\n" \
" pass" % (cls.__name__, annotation_cls) in locals()
exec "annotated_classes[cls] = Annotated%s" % (cls.__name__,)
def _deep_annotate(element, annotations, exclude=None):
"""Deep copy the given ClauseElement, annotating each element
with the given annotations dictionary.
Elements within the exclude collection will be cloned but not annotated.
"""
def clone(elem):
if exclude and \
hasattr(elem, 'proxy_set') and \
elem.proxy_set.intersection(exclude):
newelem = elem._clone()
elif annotations != elem._annotations:
newelem = elem._annotate(annotations)
else:
newelem = elem
newelem._copy_internals(clone=clone)
return newelem
if element is not None:
element = clone(element)
return element
def _deep_deannotate(element, values=None):
"""Deep copy the given element, removing annotations."""
cloned = util.column_dict()
def clone(elem):
# if a values dict is given,
# the elem must be cloned each time it appears,
# as there may be different annotations in source
# elements that are remaining. if totally
# removing all annotations, can assume the same
# slate...
if values or elem not in cloned:
newelem = elem._deannotate(values=values, clone=True)
newelem._copy_internals(clone=clone)
if not values:
cloned[elem] = newelem
return newelem
else:
return cloned[elem]
if element is not None:
element = clone(element)
return element
def _shallow_annotate(element, annotations):
"""Annotate the given ClauseElement and copy its internals so that
internal objects refer to the new annotated object.
Basically used to apply a "dont traverse" annotation to a
selectable, without digging throughout the whole
structure wasting time.
"""
element = element._annotate(annotations)
element._copy_internals()
return element
def splice_joins(left, right, stop_on=None):
if left is None:
return right
stack = [(right, None)]
adapter = ClauseAdapter(left)
ret = None
while stack:
(right, prevright) = stack.pop()
if isinstance(right, expression.Join) and right is not stop_on:
right = right._clone()
right._reset_exported()
right.onclause = adapter.traverse(right.onclause)
stack.append((right.left, right))
else:
right = adapter.traverse(right)
if prevright is not None:
prevright.left = right
if ret is None:
ret = right
return ret
def reduce_columns(columns, *clauses, **kw):
"""given a list of columns, return a 'reduced' set based on natural
equivalents.
the set is reduced to the smallest list of columns which have no natural
equivalent present in the list. A "natural equivalent" means that two
columns will ultimately represent the same value because they are related
by a foreign key.
\*clauses is an optional list of join clauses which will be traversed
to further identify columns that are "equivalent".
\**kw may specify 'ignore_nonexistent_tables' to ignore foreign keys
whose tables are not yet configured, or columns that aren't yet present.
This function is primarily used to determine the most minimal "primary key"
from a selectable, by reducing the set of primary key columns present
in the the selectable to just those that are not repeated.
"""
ignore_nonexistent_tables = kw.pop('ignore_nonexistent_tables', False)
only_synonyms = kw.pop('only_synonyms', False)
columns = util.ordered_column_set(columns)
omit = util.column_set()
for col in columns:
for fk in chain(*[c.foreign_keys for c in col.proxy_set]):
for c in columns:
if c is col:
continue
try:
fk_col = fk.column
except exc.NoReferencedColumnError:
# TODO: add specific coverage here
# to test/sql/test_selectable ReduceTest
if ignore_nonexistent_tables:
continue
else:
raise
except exc.NoReferencedTableError:
# TODO: add specific coverage here
# to test/sql/test_selectable ReduceTest
if ignore_nonexistent_tables:
continue
else:
raise
if fk_col.shares_lineage(c) and \
(not only_synonyms or \
c.name == col.name):
omit.add(col)
break
if clauses:
def visit_binary(binary):
if binary.operator == operators.eq:
cols = util.column_set(chain(*[c.proxy_set
for c in columns.difference(omit)]))
if binary.left in cols and binary.right in cols:
for c in reversed(columns):
if c.shares_lineage(binary.right) and \
(not only_synonyms or \
c.name == binary.left.name):
omit.add(c)
break
for clause in clauses:
if clause is not None:
visitors.traverse(clause, {}, {'binary': visit_binary})
return expression.ColumnSet(columns.difference(omit))
def criterion_as_pairs(expression, consider_as_foreign_keys=None,
consider_as_referenced_keys=None, any_operator=False):
"""traverse an expression and locate binary criterion pairs."""
if consider_as_foreign_keys and consider_as_referenced_keys:
raise exc.ArgumentError("Can only specify one of "
"'consider_as_foreign_keys' or "
"'consider_as_referenced_keys'")
def col_is(a, b):
#return a is b
return a.compare(b)
def visit_binary(binary):
if not any_operator and binary.operator is not operators.eq:
return
if not isinstance(binary.left, sql.ColumnElement) or \
not isinstance(binary.right, sql.ColumnElement):
return
if consider_as_foreign_keys:
if binary.left in consider_as_foreign_keys and \
(col_is(binary.right, binary.left) or
binary.right not in consider_as_foreign_keys):
pairs.append((binary.right, binary.left))
elif binary.right in consider_as_foreign_keys and \
(col_is(binary.left, binary.right) or
binary.left not in consider_as_foreign_keys):
pairs.append((binary.left, binary.right))
elif consider_as_referenced_keys:
if binary.left in consider_as_referenced_keys and \
(col_is(binary.right, binary.left) or
binary.right not in consider_as_referenced_keys):
pairs.append((binary.left, binary.right))
elif binary.right in consider_as_referenced_keys and \
(col_is(binary.left, binary.right) or
binary.left not in consider_as_referenced_keys):
pairs.append((binary.right, binary.left))
else:
if isinstance(binary.left, schema.Column) and \
isinstance(binary.right, schema.Column):
if binary.left.references(binary.right):
pairs.append((binary.right, binary.left))
elif binary.right.references(binary.left):
pairs.append((binary.left, binary.right))
pairs = []
visitors.traverse(expression, {}, {'binary': visit_binary})
return pairs
class AliasedRow(object):
"""Wrap a RowProxy with a translation map.
This object allows a set of keys to be translated
to those present in a RowProxy.
"""
def __init__(self, row, map):
# AliasedRow objects don't nest, so un-nest
# if another AliasedRow was passed
if isinstance(row, AliasedRow):
self.row = row.row
else:
self.row = row
self.map = map
def __contains__(self, key):
return self.map[key] in self.row
def has_key(self, key):
return key in self
def __getitem__(self, key):
return self.row[self.map[key]]
def keys(self):
return self.row.keys()
class ClauseAdapter(visitors.ReplacingCloningVisitor):
"""Clones and modifies clauses based on column correspondence.
E.g.::
table1 = Table('sometable', metadata,
Column('col1', Integer),
Column('col2', Integer)
)
table2 = Table('someothertable', metadata,
Column('col1', Integer),
Column('col2', Integer)
)
condition = table1.c.col1 == table2.c.col1
make an alias of table1::
s = table1.alias('foo')
calling ``ClauseAdapter(s).traverse(condition)`` converts
condition to read::
s.c.col1 == table2.c.col1
"""
def __init__(self, selectable, equivalents=None,
include=None, exclude=None,
include_fn=None, exclude_fn=None,
adapt_on_names=False):
self.__traverse_options__ = {'stop_on': [selectable]}
self.selectable = selectable
if include:
assert not include_fn
self.include_fn = lambda e: e in include
else:
self.include_fn = include_fn
if exclude:
assert not exclude_fn
self.exclude_fn = lambda e: e in exclude
else:
self.exclude_fn = exclude_fn
self.equivalents = util.column_dict(equivalents or {})
self.adapt_on_names = adapt_on_names
def _corresponding_column(self, col, require_embedded,
_seen=util.EMPTY_SET):
newcol = self.selectable.corresponding_column(
col,
require_embedded=require_embedded)
if newcol is None and col in self.equivalents and col not in _seen:
for equiv in self.equivalents[col]:
newcol = self._corresponding_column(equiv,
require_embedded=require_embedded,
_seen=_seen.union([col]))
if newcol is not None:
return newcol
if self.adapt_on_names and newcol is None:
newcol = self.selectable.c.get(col.name)
return newcol
def replace(self, col):
if isinstance(col, expression.FromClause) and \
self.selectable.is_derived_from(col):
return self.selectable
elif not isinstance(col, expression.ColumnElement):
return None
elif self.include_fn and not self.include_fn(col):
return None
elif self.exclude_fn and self.exclude_fn(col):
return None
else:
return self._corresponding_column(col, True)
class ColumnAdapter(ClauseAdapter):
"""Extends ClauseAdapter with extra utility functions.
Provides the ability to "wrap" this ClauseAdapter
around another, a columns dictionary which returns
adapted elements given an original, and an
adapted_row() factory.
"""
def __init__(self, selectable, equivalents=None,
chain_to=None, include=None,
exclude=None, adapt_required=False):
ClauseAdapter.__init__(self, selectable, equivalents, include, exclude)
if chain_to:
self.chain(chain_to)
self.columns = util.populate_column_dict(self._locate_col)
self.adapt_required = adapt_required
def wrap(self, adapter):
ac = self.__class__.__new__(self.__class__)
ac.__dict__ = self.__dict__.copy()
ac._locate_col = ac._wrap(ac._locate_col, adapter._locate_col)
ac.adapt_clause = ac._wrap(ac.adapt_clause, adapter.adapt_clause)
ac.adapt_list = ac._wrap(ac.adapt_list, adapter.adapt_list)
ac.columns = util.populate_column_dict(ac._locate_col)
return ac
adapt_clause = ClauseAdapter.traverse
adapt_list = ClauseAdapter.copy_and_process
def _wrap(self, local, wrapped):
def locate(col):
col = local(col)
return wrapped(col)
return locate
def _locate_col(self, col):
c = self._corresponding_column(col, True)
if c is None:
c = self.adapt_clause(col)
# anonymize labels in case they have a hardcoded name
if isinstance(c, expression.Label):
c = c.label(None)
# adapt_required indicates that if we got the same column
# back which we put in (i.e. it passed through),
# it's not correct. this is used by eagerloading which
# knows that all columns and expressions need to be adapted
# to a result row, and a "passthrough" is definitely targeting
# the wrong column.
if self.adapt_required and c is col:
return None
return c
def adapted_row(self, row):
return AliasedRow(row, self.columns)
def __getstate__(self):
d = self.__dict__.copy()
del d['columns']
return d
def __setstate__(self, state):
self.__dict__.update(state)
self.columns = util.PopulateDict(self._locate_col)