# sql/util.py # Copyright (C) 2005-2013 the SQLAlchemy authors and contributors # # 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 q a e a f b q b e b f j 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)