from sqlalchemy import exc,schema,topological,util,sql,types
from sqlalchemy.sql import expression,operators,visitors
from itertools import chain
"""Utility functions that build upon SQL and Schema constructs."""
def sort_tables(tables):
"""sort a collection of Table objects in order of their foreign-key dependency."""
tables = list(tables)
tuples = []
def visit_foreign_key(fkey):
if fkey.use_alter:
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})
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 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 _quote_ddl_expr(element):
if isinstance(element, basestring):
element = element.replace("'", "''")
return "'%s'" % element
else:
return repr(element)
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.
"""
def repl(element):
if isinstance(element, expression._BindParamClause):
return expression.literal_column(_quote_ddl_expr(element.value))
elif isinstance(element, expression.ColumnClause) and \
element.table is not None:
return expression.column(element.name)
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._BindParamClause) and binary.left.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._BindParamClause) and binary.right.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):
"""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: This flag will cause the
function to silently skip over foreign key resolution errors
due to nonexistent tables - the assumption is that these
tables have not yet been defined within an initialization process
and are not significant to the operation.
: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 b.foreign_keys:
try:
col = fk.get_referent(left)
except exc.NoReferencedTableError:
if ignore_nonexistent_tables:
continue
else:
raise
if col is not None:
crit.append(col == fk.parent)
constraints.add(fk.constraint)
if left is not b:
for fk in left.foreign_keys:
try:
col = fk.get_referent(b)
except exc.NoReferencedTableError:
if ignore_nonexistent_tables:
continue
else:
raise
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.ArgumentError(
"Can't find any foreign key relationships "
"between '%s' and '%s'.%s" % (a.description, b.description, hint))
elif len(constraints) > 1:
raise exc.ArgumentError(
"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__,
(Annotated, 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()
self.__element = element
self._annotations = values
def _annotate(self, values):
_values = self._annotations.copy()
_values.update(values)
clone = self.__class__.__new__(self.__class__)
clone.__dict__ = self.__dict__.copy()
clone._annotations = _values
return clone
def _deannotate(self):
return self.__element
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 occured
# to this object's __dict__.
clone.__dict__.update(self.__dict__)
return Annotated(clone, self._annotations)
def __hash__(self):
return hash(self.__element)
def __cmp__(self, other):
return cmp(hash(self.__element), hash(other))
# 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 = {}
from sqlalchemy.sql import expression
for cls in expression.__dict__.values() + [schema.Column, schema.Table]:
if isinstance(cls, type) and issubclass(cls, expression.ClauseElement):
exec "class Annotated%s(Annotated, cls):\n" \
" __visit_name__ = cls.__visit_name__\n"\
" pass" % (cls.__name__, ) 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):
# check if element is present in the exclude list.
# take into account proxying relationships.
if exclude and \
hasattr(elem, 'proxy_set') and \
elem.proxy_set.intersection(exclude):
elem = elem._clone()
elif annotations != elem._annotations:
elem = elem._annotate(annotations.copy())
elem._copy_internals(clone=clone)
return elem
if element is not None:
element = clone(element)
return element
def _deep_deannotate(element):
"""Deep copy the given element, removing all annotations."""
def clone(elem):
elem = elem._deannotate()
elem._copy_internals(clone=clone)
return elem
if element is not None:
element = clone(element)
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.
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)
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.NoReferencedTableError:
if ignore_nonexistent_tables:
continue
else:
raise
if fk_col.shares_lineage(c):
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 columns:
if c.shares_lineage(binary.right):
omit.add(c)
break
for clause in clauses:
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 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 \
(binary.right is 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 \
(binary.left is 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 \
(binary.right is 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 \
(binary.left is 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
def folded_equivalents(join, equivs=None):
"""Return a list of uniquely named columns.
The column list of the given Join will be narrowed
down to a list of all equivalently-named,
equated columns folded into one column, where 'equated' means they are
equated to each other in the ON clause of this join.
This function is used by Join.select(fold_equivalents=True).
Deprecated. This function is used for a certain kind of
"polymorphic_union" which is designed to achieve joined
table inheritance where the base table has no "discriminator"
column; [ticket:1131] will provide a better way to
achieve this.
"""
if equivs is None:
equivs = set()
def visit_binary(binary):
if binary.operator == operators.eq and binary.left.name == binary.right.name:
equivs.add(binary.right)
equivs.add(binary.left)
visitors.traverse(join.onclause, {}, {'binary':visit_binary})
collist = []
if isinstance(join.left, expression.Join):
left = folded_equivalents(join.left, equivs)
else:
left = list(join.left.columns)
if isinstance(join.right, expression.Join):
right = folded_equivalents(join.right, equivs)
else:
right = list(join.right.columns)
used = set()
for c in left + right:
if c in equivs:
if c.name not in used:
collist.append(c)
used.add(c.name)
else:
collist.append(c)
return collist
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):
self.__traverse_options__ = {'column_collections':False, 'stop_on':[selectable]}
self.selectable = selectable
self.include = include
self.exclude = exclude
self.equivalents = util.column_dict(equivalents or {})
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
return newcol
def replace(self, col):
if isinstance(col, expression.FromClause):
if self.selectable.is_derived_from(col):
return self.selectable
if not isinstance(col, expression.ColumnElement):
return None
if self.include and col not in self.include:
return None
elif self.exclude and col in self.exclude:
return None
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)
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