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# sql/util.py
# Copyright (C) 2005-2021 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 collections import deque
from itertools import chain
from . import operators
from . import visitors
from .annotation import _deep_annotate # noqa
from .annotation import _deep_deannotate # noqa
from .annotation import _shallow_annotate # noqa
from .base import _from_objects
from .base import ColumnSet
from .ddl import sort_tables # noqa
from .elements import _expand_cloned
from .elements import _find_columns # noqa
from .elements import _label_reference
from .elements import _textual_label_reference
from .elements import BindParameter
from .elements import ColumnClause
from .elements import ColumnElement
from .elements import Grouping
from .elements import Label
from .elements import Null
from .elements import UnaryExpression
from .schema import Column
from .selectable import Alias
from .selectable import FromClause
from .selectable import FromGrouping
from .selectable import Join
from .selectable import ScalarSelect
from .selectable import SelectBase
from .selectable import TableClause
from .. import exc
from .. import util
join_condition = util.langhelpers.public_factory(
Join._join_condition, ".sql.util.join_condition"
)
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))
idx = []
for i, f in enumerate(clauses):
for s in selectables:
if f.is_derived_from(s):
idx.append(i)
return idx
def find_left_clause_that_matches_given(clauses, join_from):
"""Given a list of FROM clauses and a selectable,
return the indexes from the list of
clauses which is derived from the selectable.
"""
selectables = list(_from_objects(join_from))
liberal_idx = []
for i, f in enumerate(clauses):
for s in selectables:
# basic check, if f is derived from s.
# this can be joins containing a table, or an aliased table
# or select statement matching to a table. This check
# will match a table to a selectable that is adapted from
# that table. With Query, this suits the case where a join
# is being made to an adapted entity
if f.is_derived_from(s):
liberal_idx.append(i)
break
# in an extremely small set of use cases, a join is being made where
# there are multiple FROM clauses where our target table is represented
# in more than one, such as embedded or similar. in this case, do
# another pass where we try to get a more exact match where we aren't
# looking at adaption relationships.
if len(liberal_idx) > 1:
conservative_idx = []
for idx in liberal_idx:
f = clauses[idx]
for s in selectables:
if set(surface_selectables(f)).intersection(
surface_selectables(s)
):
conservative_idx.append(idx)
break
if conservative_idx:
return conservative_idx
return liberal_idx
def find_left_clause_to_join_from(clauses, join_to, onclause):
"""Given a list of FROM clauses, a selectable,
and optional ON clause, return a list of integer indexes from the
clauses list indicating the clauses that can be joined from.
The presence of an "onclause" indicates that at least one clause can
definitely be joined from; if the list of clauses is of length one
and the onclause is given, returns that index. If the list of clauses
is more than length one, and the onclause is given, attempts to locate
which clauses contain the same columns.
"""
idx = []
selectables = set(_from_objects(join_to))
# if we are given more than one target clause to join
# from, use the onclause to provide a more specific answer.
# otherwise, don't try to limit, after all, "ON TRUE" is a valid
# on clause
if len(clauses) > 1 and onclause is not None:
resolve_ambiguity = True
cols_in_onclause = _find_columns(onclause)
else:
resolve_ambiguity = False
cols_in_onclause = None
for i, f in enumerate(clauses):
for s in selectables.difference([f]):
if resolve_ambiguity:
if set(f.c).union(s.c).issuperset(cols_in_onclause):
idx.append(i)
break
elif Join._can_join(f, s) or onclause is not None:
idx.append(i)
break
if len(idx) > 1:
# this is the same "hide froms" logic from
# Selectable._get_display_froms
toremove = set(
chain(*[_expand_cloned(f._hide_froms) for f in clauses])
)
idx = [i for i in idx if clauses[i] not in toremove]
# onclause was given and none of them resolved, so assume
# all indexes can match
if not idx and onclause is not None:
return range(len(clauses))
else:
return idx
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))
visit = None # remove gc cycles
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()
result = []
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) and not isinstance(
t.element, ScalarSelect
):
t = t.element
if isinstance(t, Grouping):
t = t.element
stack.append(t)
continue
if isinstance(t, _label_reference):
t = t.element
if isinstance(t, (_textual_label_reference)):
continue
if t not in cols:
cols.add(t)
result.append(t)
else:
for c in t.get_children():
stack.append(c)
return result
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 expand_column_list_from_order_by(collist, order_by):
"""Given the columns clause and ORDER BY of a selectable,
return a list of column expressions that can be added to the collist
corresponding to the ORDER BY, without repeating those already
in the collist.
"""
cols_already_present = set(
[
col.element if col._order_by_label_element is not None else col
for col in collist
]
)
to_look_for = list(chain(*[unwrap_order_by(o) for o in order_by]))
return [col for col in to_look_for if col not in cols_already_present]
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 tables_from_leftmost(clause):
if isinstance(clause, Join):
for t in tables_from_leftmost(clause.left):
yield t
for t in tables_from_leftmost(clause.right):
yield t
elif isinstance(clause, FromGrouping):
for t in tables_from_leftmost(clause.element):
yield t
else:
yield clause
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 surface_selectables_only(clause):
stack = [clause]
while stack:
elem = stack.pop()
if isinstance(elem, (TableClause, Alias)):
yield elem
if isinstance(elem, Join):
stack.extend((elem.left, elem.right))
elif isinstance(elem, FromGrouping):
stack.append(elem.element)
elif isinstance(elem, ColumnClause):
if elem.table is not None:
stack.append(elem.table)
else:
yield elem
elif elem is not None:
yield elem
def surface_column_elements(clause, include_scalar_selects=True):
"""traverse and yield only outer-exposed column elements, such as would
be addressable in the WHERE clause of a SELECT if this element were
in the columns clause."""
filter_ = (FromGrouping,)
if not include_scalar_selects:
filter_ += (SelectBase,)
stack = deque([clause])
while stack:
elem = stack.popleft()
yield elem
for sub in elem.get_children():
if isinstance(sub, filter_):
continue
stack.append(sub)
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_base(object):
_LIST = 0
_TUPLE = 1
_DICT = 2
__slots__ = ("max_chars",)
def trunc(self, value):
rep = repr(value)
lenrep = len(rep)
if lenrep > self.max_chars:
segment_length = self.max_chars // 2
rep = (
rep[0:segment_length]
+ (
" ... (%d characters truncated) ... "
% (lenrep - self.max_chars)
)
+ rep[-segment_length:]
)
return rep
class _repr_row(_repr_base):
"""Provide a string view of a row."""
__slots__ = ("row",)
def __init__(self, row, max_chars=300):
self.row = row
self.max_chars = max_chars
def __repr__(self):
trunc = self.trunc
return "(%s%s)" % (
", ".join(trunc(value) for value in self.row),
"," if len(self.row) == 1 else "",
)
class _repr_params(_repr_base):
"""Provide a string view of bound parameters.
Truncates display to a given numnber of 'multi' parameter sets,
as well as long values to a given number of characters.
"""
__slots__ = "params", "batches", "ismulti"
def __init__(self, params, batches, max_chars=300, ismulti=None):
self.params = params
self.ismulti = ismulti
self.batches = batches
self.max_chars = max_chars
def __repr__(self):
if self.ismulti is None:
return self.trunc(self.params)
if isinstance(self.params, list):
typ = self._LIST
elif isinstance(self.params, tuple):
typ = self._TUPLE
elif isinstance(self.params, dict):
typ = self._DICT
else:
return self.trunc(self.params)
if self.ismulti and len(self.params) > self.batches:
msg = " ... displaying %i of %i total bound parameter sets ... "
return " ".join(
(
self._repr_multi(self.params[: self.batches - 2], typ)[
0:-1
],
msg % (self.batches, len(self.params)),
self._repr_multi(self.params[-2:], typ)[1:],
)
)
elif self.ismulti:
return self._repr_multi(self.params, typ)
else:
return self._repr_params(self.params, typ)
def _repr_multi(self, multi_params, typ):
if multi_params:
if isinstance(multi_params[0], list):
elem_type = self._LIST
elif isinstance(multi_params[0], tuple):
elem_type = self._TUPLE
elif isinstance(multi_params[0], dict):
elem_type = self._DICT
else:
assert False, "Unknown parameter type %s" % (
type(multi_params[0])
)
elements = ", ".join(
self._repr_params(params, elem_type) for params in multi_params
)
else:
elements = ""
if typ == self._LIST:
return "[%s]" % elements
else:
return "(%s)" % elements
def _repr_params(self, params, typ):
trunc = self.trunc
if typ is self._DICT:
return "{%s}" % (
", ".join(
"%r: %s" % (key, trunc(value))
for key, value in params.items()
)
)
elif typ is self._TUPLE:
return "(%s%s)" % (
", ".join(trunc(value) for value in params),
"," if len(params) == 1 else "",
)
else:
return "[%s]" % (", ".join(trunc(value) for value in 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):
r"""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,
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,
)
self.columns = util.WeakPopulateDict(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.WeakPopulateDict(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.WeakPopulateDict(self._locate_col)
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