sqlalchemy.util.defaultdict

Here are the examples of the python api sqlalchemy.util.defaultdict taken from open source projects. By voting up you can indicate which examples are most useful and appropriate.

17 Examples 7

Example 1

Project: SickGear Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        # Query to extract the details of each UK/FK of the given table
        fkqry = """
        SELECT rc.rdb$constraint_name AS cname,
               cse.rdb$field_name AS fname,
               ix2.rdb$relation_name AS targetrname,
               se.rdb$field_name AS targetfname
        FROM rdb$relation_constraints rc
             JOIN rdb$indices ix1 ON ix1.rdb$index_name=rc.rdb$index_name
             JOIN rdb$indices ix2 ON ix2.rdb$index_name=ix1.rdb$foreign_key
             JOIN rdb$index_segments cse ON
                        cse.rdb$index_name=ix1.rdb$index_name
             JOIN rdb$index_segments se
                  ON se.rdb$index_name=ix2.rdb$index_name
                     AND se.rdb$field_position=cse.rdb$field_position
        WHERE rc.rdb$constraint_type=? AND rc.rdb$relation_name=?
        ORDER BY se.rdb$index_name, se.rdb$field_position
        """
        tablename = self.denormalize_name(table_name)

        c = connection.execute(fkqry, ["FOREIGN KEY", tablename])
        fks = util.defaultdict(lambda: {
            'name': None,
            'constrained_columns': [],
            'referred_schema': None,
            'referred_table': None,
            'referred_columns': []
        })

        for row in c:
            cname = self.normalize_name(row['cname'])
            fk = fks[cname]
            if not fk['name']:
                fk['name'] = cname
                fk['referred_table'] = self.normalize_name(row['targetrname'])
            fk['constrained_columns'].append(
                                self.normalize_name(row['fname']))
            fk['referred_columns'].append(
                                self.normalize_name(row['targetfname']))
        return list(fks.values())

Example 2

Project: SickGear Source File: base.py
    @reflection.cache
    def get_indexes(self, connection, table_name, schema=None, **kw):
        qry = """
        SELECT ix.rdb$index_name AS index_name,
               ix.rdb$unique_flag AS unique_flag,
               ic.rdb$field_name AS field_name
        FROM rdb$indices ix
             JOIN rdb$index_segments ic
                  ON ix.rdb$index_name=ic.rdb$index_name
             LEFT OUTER JOIN rdb$relation_constraints
                  ON rdb$relation_constraints.rdb$index_name =
                        ic.rdb$index_name
        WHERE ix.rdb$relation_name=? AND ix.rdb$foreign_key IS NULL
          AND rdb$relation_constraints.rdb$constraint_type IS NULL
        ORDER BY index_name, ic.rdb$field_position
        """
        c = connection.execute(qry, [self.denormalize_name(table_name)])

        indexes = util.defaultdict(dict)
        for row in c:
            indexrec = indexes[row['index_name']]
            if 'name' not in indexrec:
                indexrec['name'] = self.normalize_name(row['index_name'])
                indexrec['column_names'] = []
                indexrec['unique'] = bool(row['unique_flag'])

            indexrec['column_names'].append(
                                self.normalize_name(row['field_name']))

        return list(indexes.values())

Example 3

Project: SickGear Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        """

        kw arguments can be:

            oracle_resolve_synonyms

            dblink

        """

        requested_schema = schema  # to check later on
        resolve_synonyms = kw.get('oracle_resolve_synonyms', False)
        dblink = kw.get('dblink', '')
        info_cache = kw.get('info_cache')

        (table_name, schema, dblink, synonym) = \
            self._prepare_reflection_args(connection, table_name, schema,
                                          resolve_synonyms, dblink,
                                          info_cache=info_cache)

        constraint_data = self._get_constraint_data(connection, table_name,
                                                schema, dblink,
                                                info_cache=kw.get('info_cache'))

        def fkey_rec():
            return {
                'name': None,
                'constrained_columns': [],
                'referred_schema': None,
                'referred_table': None,
                'referred_columns': []
            }

        fkeys = util.defaultdict(fkey_rec)

        for row in constraint_data:
            (cons_name, cons_type, local_column, remote_table, remote_column, remote_owner) = \
                    row[0:2] + tuple([self.normalize_name(x) for x in row[2:6]])

            if cons_type == 'R':
                if remote_table is None:
                    # ticket 363
                    util.warn(
                        ("Got 'None' querying 'table_name' from "
                         "all_cons_columns%(dblink)s - does the user have "
                         "proper rights to the table?") % {'dblink': dblink})
                    continue

                rec = fkeys[cons_name]
                rec['name'] = cons_name
                local_cols, remote_cols = rec['constrained_columns'], rec['referred_columns']

                if not rec['referred_table']:
                    if resolve_synonyms:
                        ref_remote_name, ref_remote_owner, ref_dblink, ref_synonym = \
                                self._resolve_synonym(
                                    connection,
                                    desired_owner=self.denormalize_name(remote_owner),
                                    desired_table=self.denormalize_name(remote_table)
                                )
                        if ref_synonym:
                            remote_table = self.normalize_name(ref_synonym)
                            remote_owner = self.normalize_name(ref_remote_owner)

                    rec['referred_table'] = remote_table

                    if requested_schema is not None or self.denormalize_name(remote_owner) != schema:
                        rec['referred_schema'] = remote_owner

                local_cols.append(local_column)
                remote_cols.append(remote_column)

        return list(fkeys.values())

Example 4

Project: sqlalchemy Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        # Query to extract the details of each UK/FK of the given table
        fkqry = """
        SELECT rc.rdb$constraint_name AS cname,
               cse.rdb$field_name AS fname,
               ix2.rdb$relation_name AS targetrname,
               se.rdb$field_name AS targetfname
        FROM rdb$relation_constraints rc
             JOIN rdb$indices ix1 ON ix1.rdb$index_name=rc.rdb$index_name
             JOIN rdb$indices ix2 ON ix2.rdb$index_name=ix1.rdb$foreign_key
             JOIN rdb$index_segments cse ON
                        cse.rdb$index_name=ix1.rdb$index_name
             JOIN rdb$index_segments se
                  ON se.rdb$index_name=ix2.rdb$index_name
                     AND se.rdb$field_position=cse.rdb$field_position
        WHERE rc.rdb$constraint_type=? AND rc.rdb$relation_name=?
        ORDER BY se.rdb$index_name, se.rdb$field_position
        """
        tablename = self.denormalize_name(table_name)

        c = connection.execute(fkqry, ["FOREIGN KEY", tablename])
        fks = util.defaultdict(lambda: {
            'name': None,
            'constrained_columns': [],
            'referred_schema': None,
            'referred_table': None,
            'referred_columns': []
        })

        for row in c:
            cname = self.normalize_name(row['cname'])
            fk = fks[cname]
            if not fk['name']:
                fk['name'] = cname
                fk['referred_table'] = self.normalize_name(row['targetrname'])
            fk['constrained_columns'].append(
                self.normalize_name(row['fname']))
            fk['referred_columns'].append(
                self.normalize_name(row['targetfname']))
        return list(fks.values())

Example 5

Project: sqlalchemy Source File: base.py
    @reflection.cache
    def get_indexes(self, connection, table_name, schema=None, **kw):
        qry = """
        SELECT ix.rdb$index_name AS index_name,
               ix.rdb$unique_flag AS unique_flag,
               ic.rdb$field_name AS field_name
        FROM rdb$indices ix
             JOIN rdb$index_segments ic
                  ON ix.rdb$index_name=ic.rdb$index_name
             LEFT OUTER JOIN rdb$relation_constraints
                  ON rdb$relation_constraints.rdb$index_name =
                        ic.rdb$index_name
        WHERE ix.rdb$relation_name=? AND ix.rdb$foreign_key IS NULL
          AND rdb$relation_constraints.rdb$constraint_type IS NULL
        ORDER BY index_name, ic.rdb$field_position
        """
        c = connection.execute(qry, [self.denormalize_name(table_name)])

        indexes = util.defaultdict(dict)
        for row in c:
            indexrec = indexes[row['index_name']]
            if 'name' not in indexrec:
                indexrec['name'] = self.normalize_name(row['index_name'])
                indexrec['column_names'] = []
                indexrec['unique'] = bool(row['unique_flag'])

            indexrec['column_names'].append(
                self.normalize_name(row['field_name']))

        return list(indexes.values())

Example 6

Project: sqlalchemy_exasol Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        schema_int = schema or connection.engine.url.database
        if schema_int is None:
            schema_int = connection.execute("select CURRENT_SCHEMA from dual").scalar()
        table_name=self.denormalize_name(table_name)
        def fkey_rec():
            return {
                'name': None,
                'constrained_columns': [],
                'referred_schema': None,
                'referred_table': None,
                'referred_columns': []
            }

        fkeys = util.defaultdict(fkey_rec)

        for row in self._get_all_constraints(connection, schema=schema, info_cache=kw.get("info_cache")):
            if (row[5] != table_name and table_name is not None) or row[6] != 'FOREIGN KEY':
                continue
            (cons_name, local_column, remote_schema, remote_table, remote_column) = \
                    (row[0], row[1], row[2], row[3], row[4])
            rec = fkeys[self.normalize_name(cons_name)]
            rec['name'] = self.normalize_name(cons_name)
            local_cols, remote_cols = rec['constrained_columns'], rec['referred_columns']

            if not rec['referred_table']:
                rec['referred_table'] = self.normalize_name(remote_table)
                # we need to take care of calls without schema. the sqla test suite
                # expects referred_schema to be None if None is passed in to this function
                if schema is None and self.normalize_name(schema_int) == self.normalize_name(remote_schema):
                    rec['referred_schema'] = None
                else:
                    rec['referred_schema'] = self.normalize_name(remote_schema)

            local_cols.append(self.normalize_name(local_column))
            remote_cols.append(self.normalize_name(remote_column))

        return list(fkeys.values())

Example 7

Project: CouchPotatoV1 Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        # Query to extract the details of each UK/FK of the given table
        fkqry = """
        SELECT rc.rdb$constraint_name AS cname,
               cse.rdb$field_name AS fname,
               ix2.rdb$relation_name AS targetrname,
               se.rdb$field_name AS targetfname
        FROM rdb$relation_constraints rc
             JOIN rdb$indices ix1 ON ix1.rdb$index_name=rc.rdb$index_name
             JOIN rdb$indices ix2 ON ix2.rdb$index_name=ix1.rdb$foreign_key
             JOIN rdb$index_segments cse ON
                        cse.rdb$index_name=ix1.rdb$index_name
             JOIN rdb$index_segments se
                  ON se.rdb$index_name=ix2.rdb$index_name
                     AND se.rdb$field_position=cse.rdb$field_position
        WHERE rc.rdb$constraint_type=? AND rc.rdb$relation_name=?
        ORDER BY se.rdb$index_name, se.rdb$field_position
        """
        tablename = self.denormalize_name(table_name)

        c = connection.execute(fkqry, ["FOREIGN KEY", tablename])
        fks = util.defaultdict(lambda:{
            'name' : None,
            'constrained_columns' : [],
            'referred_schema' : None,
            'referred_table' : None,
            'referred_columns' : []
        })

        for row in c:
            cname = self.normalize_name(row['cname'])
            fk = fks[cname]
            if not fk['name']:
                fk['name'] = cname
                fk['referred_table'] = self.normalize_name(row['targetrname'])
            fk['constrained_columns'].append(
                                self.normalize_name(row['fname']))
            fk['referred_columns'].append(
                                self.normalize_name(row['targetfname']))
        return fks.values()

Example 8

Project: CouchPotatoV1 Source File: base.py
Function: get_indexes
    @reflection.cache
    def get_indexes(self, connection, table_name, schema=None, **kw):
        qry = """
        SELECT ix.rdb$index_name AS index_name,
               ix.rdb$unique_flag AS unique_flag,
               ic.rdb$field_name AS field_name
        FROM rdb$indices ix
             JOIN rdb$index_segments ic
                  ON ix.rdb$index_name=ic.rdb$index_name
             LEFT OUTER JOIN rdb$relation_constraints
                  ON rdb$relation_constraints.rdb$index_name =
                        ic.rdb$index_name
        WHERE ix.rdb$relation_name=? AND ix.rdb$foreign_key IS NULL
          AND rdb$relation_constraints.rdb$constraint_type IS NULL
        ORDER BY index_name, field_name
        """
        c = connection.execute(qry, [self.denormalize_name(table_name)])

        indexes = util.defaultdict(dict)
        for row in c:
            indexrec = indexes[row['index_name']]
            if 'name' not in indexrec:
                indexrec['name'] = self.normalize_name(row['index_name'])
                indexrec['column_names'] = []
                indexrec['unique'] = bool(row['unique_flag'])

            indexrec['column_names'].append(
                                self.normalize_name(row['field_name']))

        return indexes.values()

Example 9

Project: CouchPotatoV1 Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        schema_sel = schema or self.default_schema_name
        c = connection.execute(
        """select t1.constrname as cons_name,
                 t4.colname as local_column, t7.tabname as remote_table,
                 t6.colname as remote_column, t7.owner as remote_owner 
            from sysconstraints as t1 , systables as t2 ,
                 sysindexes as t3 , syscolumns as t4 ,
                 sysreferences as t5 , syscolumns as t6 , systables as t7 ,
                 sysconstraints as t8 , sysindexes as t9
           where t1.tabid = t2.tabid and t2.tabname=? and t2.owner=? and t1.constrtype = 'R'
             and t3.tabid = t2.tabid and t3.idxname = t1.idxname
             and t4.tabid = t2.tabid and t4.colno in (t3.part1, t3.part2, t3.part3,
             t3.part4, t3.part5, t3.part6, t3.part7, t3.part8, t3.part9, t3.part10,
             t3.part11, t3.part11, t3.part12, t3.part13, t3.part4, t3.part15, t3.part16) 
             and t5.constrid = t1.constrid and t8.constrid = t5.primary
             and t6.tabid = t5.ptabid and t6.colno in (t9.part1, t9.part2, t9.part3,
             t9.part4, t9.part5, t9.part6, t9.part7, t9.part8, t9.part9, t9.part10,
             t9.part11, t9.part11, t9.part12, t9.part13, t9.part4, t9.part15, t9.part16) and t9.idxname =
             t8.idxname
             and t7.tabid = t5.ptabid""", table_name, schema_sel)


        def fkey_rec():
            return {
                 'name' : None,
                 'constrained_columns' : [],
                 'referred_schema' : None,
                 'referred_table' : None,
                 'referred_columns' : []
             }

        fkeys = util.defaultdict(fkey_rec)

        rows = c.fetchall()
        for cons_name, local_column, \
                    remote_table, remote_column, remote_owner in rows:

            rec = fkeys[cons_name]
            rec['name'] = cons_name
            local_cols, remote_cols = \
                        rec['constrained_columns'], rec['referred_columns']

            if not rec['referred_table']:
                rec['referred_table'] = remote_table
                if schema is not None:
                    rec['referred_schema'] = remote_owner

            if local_column not in local_cols:
                local_cols.append(local_column)
            if remote_column not in remote_cols:
                remote_cols.append(remote_column)

        return fkeys.values()

Example 10

Project: CouchPotatoV1 Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        """

        kw arguments can be:

            oracle_resolve_synonyms

            dblink

        """

        requested_schema = schema # to check later on
        resolve_synonyms = kw.get('oracle_resolve_synonyms', False)
        dblink = kw.get('dblink', '')
        info_cache = kw.get('info_cache')

        (table_name, schema, dblink, synonym) = \
            self._prepare_reflection_args(connection, table_name, schema,
                                          resolve_synonyms, dblink,
                                          info_cache=info_cache)

        constraint_data = self._get_constraint_data(connection, table_name,
                                                schema, dblink,
                                                info_cache=kw.get('info_cache'))

        def fkey_rec():
            return {
                'name' : None,
                'constrained_columns' : [],
                'referred_schema' : None,
                'referred_table' : None,
                'referred_columns' : []
            }

        fkeys = util.defaultdict(fkey_rec)
        
        for row in constraint_data:
            (cons_name, cons_type, local_column, remote_table, remote_column, remote_owner) = \
                    row[0:2] + tuple([self.normalize_name(x) for x in row[2:6]])

            if cons_type == 'R':
                if remote_table is None:
                    # ticket 363
                    util.warn(
                        ("Got 'None' querying 'table_name' from "
                         "all_cons_columns%(dblink)s - does the user have "
                         "proper rights to the table?") % {'dblink':dblink})
                    continue

                rec = fkeys[cons_name]
                rec['name'] = cons_name
                local_cols, remote_cols = rec['constrained_columns'], rec['referred_columns']

                if not rec['referred_table']:
                    if resolve_synonyms:
                        ref_remote_name, ref_remote_owner, ref_dblink, ref_synonym = \
                                self._resolve_synonym(
                                    connection, 
                                    desired_owner=self.denormalize_name(remote_owner), 
                                    desired_table=self.denormalize_name(remote_table)
                                )
                        if ref_synonym:
                            remote_table = self.normalize_name(ref_synonym)
                            remote_owner = self.normalize_name(ref_remote_owner)
                    
                    rec['referred_table'] = remote_table
                    
                    if requested_schema is not None or self.denormalize_name(remote_owner) != schema:
                        rec['referred_schema'] = remote_owner
                
                local_cols.append(local_column)
                remote_cols.append(remote_column)

        return fkeys.values()

Example 11

Project: CouchPotatoV1 Source File: topological.py
Function: sort_as_subsets
def sort_as_subsets(tuples, allitems):

    edges = util.defaultdict(set)
    for parent, child in tuples:
        edges[child].add(parent)
    
    todo = set(allitems)

    while todo:
        output = set()
        for node in list(todo):
            if not todo.intersection(edges[node]):
                output.add(node)

        if not output:
            raise CircularDependencyError(
                    "Circular dependency detected",
                    find_cycles(tuples, allitems), 
                    _gen_edges(edges)
                )

        todo.difference_update(output)
        yield output

Example 12

Project: CouchPotatoV1 Source File: topological.py
Function: find_cycles
def find_cycles(tuples, allitems):
    # straight from gvr with some mods
    todo = set(allitems)

    edges = util.defaultdict(set)
    for parent, child in tuples:
        edges[parent].add(child)

    output = set()
    
    while todo:
        node = todo.pop()
        stack = [node]
        while stack:
            top = stack[-1]
            for node in edges[top]:
                if node in stack:
                    cyc = stack[stack.index(node):]
                    todo.difference_update(cyc)
                    output.update(cyc)
                    
                if node in todo:
                    stack.append(node)
                    todo.remove(node)
                    break
            else:
                node = stack.pop()
    return output

Example 13

Project: kokoropy Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        """

        kw arguments can be:

            oracle_resolve_synonyms

            dblink

        """

        requested_schema = schema  # to check later on
        resolve_synonyms = kw.get('oracle_resolve_synonyms', False)
        dblink = kw.get('dblink', '')
        info_cache = kw.get('info_cache')

        (table_name, schema, dblink, synonym) = \
            self._prepare_reflection_args(connection, table_name, schema,
                                          resolve_synonyms, dblink,
                                          info_cache=info_cache)

        constraint_data = self._get_constraint_data(
            connection, table_name, schema, dblink,
            info_cache=kw.get('info_cache'))

        def fkey_rec():
            return {
                'name': None,
                'constrained_columns': [],
                'referred_schema': None,
                'referred_table': None,
                'referred_columns': []
            }

        fkeys = util.defaultdict(fkey_rec)

        for row in constraint_data:
            (cons_name, cons_type, local_column, remote_table, remote_column, remote_owner) = \
                row[0:2] + tuple([self.normalize_name(x) for x in row[2:6]])

            if cons_type == 'R':
                if remote_table is None:
                    # ticket 363
                    util.warn(
                        ("Got 'None' querying 'table_name' from "
                         "all_cons_columns%(dblink)s - does the user have "
                         "proper rights to the table?") % {'dblink': dblink})
                    continue

                rec = fkeys[cons_name]
                rec['name'] = cons_name
                local_cols, remote_cols = rec[
                    'constrained_columns'], rec['referred_columns']

                if not rec['referred_table']:
                    if resolve_synonyms:
                        ref_remote_name, ref_remote_owner, ref_dblink, ref_synonym = \
                            self._resolve_synonym(
                                connection,
                                desired_owner=self.denormalize_name(
                                    remote_owner),
                                desired_table=self.denormalize_name(
                                    remote_table)
                            )
                        if ref_synonym:
                            remote_table = self.normalize_name(ref_synonym)
                            remote_owner = self.normalize_name(
                                ref_remote_owner)

                    rec['referred_table'] = remote_table

                    if requested_schema is not None or \
                       self.denormalize_name(remote_owner) != schema:
                        rec['referred_schema'] = remote_owner

                local_cols.append(local_column)
                remote_cols.append(remote_column)

        return list(fkeys.values())

Example 14

Project: maraschino Source File: base.py
    @reflection.cache
    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        """

        kw arguments can be:

            oracle_resolve_synonyms

            dblink

        """

        requested_schema = schema # to check later on
        resolve_synonyms = kw.get('oracle_resolve_synonyms', False)
        dblink = kw.get('dblink', '')
        info_cache = kw.get('info_cache')

        (table_name, schema, dblink, synonym) = \
            self._prepare_reflection_args(connection, table_name, schema,
                                          resolve_synonyms, dblink,
                                          info_cache=info_cache)

        constraint_data = self._get_constraint_data(connection, table_name,
                                                schema, dblink,
                                                info_cache=kw.get('info_cache'))

        def fkey_rec():
            return {
                'name' : None,
                'constrained_columns' : [],
                'referred_schema' : None,
                'referred_table' : None,
                'referred_columns' : []
            }

        fkeys = util.defaultdict(fkey_rec)

        for row in constraint_data:
            (cons_name, cons_type, local_column, remote_table, remote_column, remote_owner) = \
                    row[0:2] + tuple([self.normalize_name(x) for x in row[2:6]])

            if cons_type == 'R':
                if remote_table is None:
                    # ticket 363
                    util.warn(
                        ("Got 'None' querying 'table_name' from "
                         "all_cons_columns%(dblink)s - does the user have "
                         "proper rights to the table?") % {'dblink':dblink})
                    continue

                rec = fkeys[cons_name]
                rec['name'] = cons_name
                local_cols, remote_cols = rec['constrained_columns'], rec['referred_columns']

                if not rec['referred_table']:
                    if resolve_synonyms:
                        ref_remote_name, ref_remote_owner, ref_dblink, ref_synonym = \
                                self._resolve_synonym(
                                    connection, 
                                    desired_owner=self.denormalize_name(remote_owner), 
                                    desired_table=self.denormalize_name(remote_table)
                                )
                        if ref_synonym:
                            remote_table = self.normalize_name(ref_synonym)
                            remote_owner = self.normalize_name(ref_remote_owner)

                    rec['referred_table'] = remote_table

                    if requested_schema is not None or self.denormalize_name(remote_owner) != schema:
                        rec['referred_schema'] = remote_owner

                local_cols.append(local_column)
                remote_cols.append(remote_column)

        return fkeys.values()

Example 15

Project: maraschino Source File: event.py
Function: init
    def __init__(self, fn):
        self.__name__ = fn.__name__
        self.__doc__ = fn.__doc__
        self._clslevel = util.defaultdict(list)

Example 16

Project: maraschino Source File: topological.py
Function: sort_as_subsets
def sort_as_subsets(tuples, allitems):

    edges = util.defaultdict(set)
    for parent, child in tuples:
        edges[child].add(parent)

    todo = set(allitems)

    while todo:
        output = set()
        for node in list(todo):
            if not todo.intersection(edges[node]):
                output.add(node)

        if not output:
            raise CircularDependencyError(
                    "Circular dependency detected.",
                    find_cycles(tuples, allitems), 
                    _gen_edges(edges)
                )

        todo.difference_update(output)
        yield output

Example 17

Project: maraschino Source File: topological.py
Function: find_cycles
def find_cycles(tuples, allitems):
    # straight from gvr with some mods

    edges = util.defaultdict(set)
    for parent, child in tuples:
        edges[parent].add(child)
    nodes_to_test = set(edges)

    output = set()

    # we'd like to find all nodes that are 
    # involved in cycles, so we do the full
    # pass through the whole thing for each
    # node in the original list.

    # we can go just through parent edge nodes.
    # if a node is only a child and never a parent,
    # by definition it can't be part of a cycle.  same
    # if it's not in the edges at all.
    for node in nodes_to_test:
        stack = [node]
        todo = nodes_to_test.difference(stack)
        while stack:
            top = stack[-1]
            for node in edges[top]:
                if node in stack:
                    cyc = stack[stack.index(node):]
                    todo.difference_update(cyc)
                    output.update(cyc)

                if node in todo:
                    stack.append(node)
                    todo.remove(node)
                    break
            else:
                node = stack.pop()
    return output