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# sql/util.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
"""High level utilities which build upon other modules here.
"""
from .. import exc, util
from .base import _from_objects, ColumnSet
from . import operators, visitors
from itertools import chain
from collections import deque
from .elements import BindParameter, ColumnClause, ColumnElement, \
Null, UnaryExpression, literal_column, Label, _label_reference, \
_textual_label_reference
from .selectable import ScalarSelect, Join, FromClause, FromGrouping
from .schema import Column
join_condition = util.langhelpers.public_factory(
Join._join_condition,
".sql.util.join_condition")
# names that are still being imported from the outside
from .annotation import _shallow_annotate, _deep_annotate, _deep_deannotate
from .elements import _find_columns
from .ddl import sort_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(_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, ScalarSelect):
# we don't 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, 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 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, ColumnElement) and \
(
not isinstance(t, UnaryExpression) or
not operators.is_ordering_modifier(t.modifier)
):
if isinstance(t, _label_reference):
t = t.element
if isinstance(t, (_textual_label_reference)):
continue
cols.add(t)
else:
for c in t.get_children():
stack.append(c)
return cols
def unwrap_label_reference(element):
def replace(elem):
if isinstance(elem, (_label_reference, _textual_label_reference)):
return elem.element
return visitors.replacement_traverse(
element, {}, replace
)
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.
"""
for elem in surface_selectables(search):
if clause == elem: # use == here so that Annotated's compare
return True
else:
return False
def surface_selectables(clause):
stack = [clause]
while stack:
elem = stack.pop()
yield elem
if isinstance(elem, Join):
stack.extend((elem.left, elem.right))
elif isinstance(elem, FromGrouping):
stack.append(elem.element)
def selectables_overlap(left, right):
"""Return True if left/right have some overlapping selectable"""
return bool(
set(surface_selectables(left)).intersection(
surface_selectables(right)
)
)
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, util.string_types):
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 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, BindParameter) \
and binary.left._identifying_key in nulls:
# reverse order if the NULL is on the left side
binary.left = binary.right
binary.right = Null()
binary.operator = operators.is_
binary.negate = operators.isnot
elif isinstance(binary.right, BindParameter) \
and binary.right._identifying_key in nulls:
binary.right = Null()
binary.operator = operators.is_
binary.negate = operators.isnot
return visitors.cloned_traverse(crit, {}, {'binary': visit_binary})
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, 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 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 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, ColumnElement) or \
not isinstance(binary.right, 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, Column) and \
isinstance(binary.right, 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 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_fn=None, exclude_fn=None,
adapt_on_names=False, anonymize_labels=False):
self.__traverse_options__ = {
'stop_on': [selectable],
'anonymize_labels': anonymize_labels}
self.selectable = selectable
self.include_fn = include_fn
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, FromClause) and \
self.selectable.is_derived_from(col):
return self.selectable
elif not isinstance(col, 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.
Key aspects of ColumnAdapter include:
* Expressions that are adapted are stored in a persistent
.columns collection; so that an expression E adapted into
an expression E1, will return the same object E1 when adapted
a second time. This is important in particular for things like
Label objects that are anonymized, so that the ColumnAdapter can
be used to present a consistent "adapted" view of things.
* Exclusion of items from the persistent collection based on
include/exclude rules, but also independent of hash identity.
This because "annotated" items all have the same hash identity as their
parent.
* "wrapping" capability is added, so that the replacement of an expression
E can proceed through a series of adapters. This differs from the
visitor's "chaining" feature in that the resulting object is passed
through all replacing functions unconditionally, rather than stopping
at the first one that returns non-None.
* An adapt_required option, used by eager loading to indicate that
We don't trust a result row column that is not translated.
This is to prevent a column from being interpreted as that
of the child row in a self-referential scenario, see
inheritance/test_basic.py->EagerTargetingTest.test_adapt_stringency
"""
def __init__(self, selectable, equivalents=None,
chain_to=None, adapt_required=False,
include_fn=None, exclude_fn=None,
adapt_on_names=False,
allow_label_resolve=True,
anonymize_labels=False):
ClauseAdapter.__init__(self, selectable, equivalents,
include_fn=include_fn, exclude_fn=exclude_fn,
adapt_on_names=adapt_on_names,
anonymize_labels=anonymize_labels)
if chain_to:
self.chain(chain_to)
self.columns = util.populate_column_dict(self._locate_col)
if self.include_fn or self.exclude_fn:
self.columns = self._IncludeExcludeMapping(self, self.columns)
self.adapt_required = adapt_required
self.allow_label_resolve = allow_label_resolve
self._wrap = None
class _IncludeExcludeMapping(object):
def __init__(self, parent, columns):
self.parent = parent
self.columns = columns
def __getitem__(self, key):
if (
self.parent.include_fn and not self.parent.include_fn(key)
) or (
self.parent.exclude_fn and self.parent.exclude_fn(key)
):
if self.parent._wrap:
return self.parent._wrap.columns[key]
else:
return key
return self.columns[key]
def wrap(self, adapter):
ac = self.__class__.__new__(self.__class__)
ac.__dict__.update(self.__dict__)
ac._wrap = adapter
ac.columns = util.populate_column_dict(ac._locate_col)
if ac.include_fn or ac.exclude_fn:
ac.columns = self._IncludeExcludeMapping(ac, ac.columns)
return ac
def traverse(self, obj):
return self.columns[obj]
adapt_clause = traverse
adapt_list = ClauseAdapter.copy_and_process
def _locate_col(self, col):
c = ClauseAdapter.traverse(self, col)
if self._wrap:
c2 = self._wrap._locate_col(c)
if c2 is not None:
c = c2
if self.adapt_required and c is col:
return None
c._allow_label_resolve = self.allow_label_resolve
return c
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)
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