Python django.utils.six.moves 模块，zip() 实例源码

def previous_current_next(items):
    """
    From http://www.wordaligned.org/articles/zippy-triples-served-with-python

    Creates an iterator which returns (previous, current, next) triples,
    with ``None`` filling in when there is no previous or next
    available.
    """
    extend = itertools.chain([None], items, [None])
    prev, cur, nex = itertools.tee(extend, 3)
    # Advancing an iterator twice when we know there are two items (the
    # two Nones at the start and at the end) will never fail except if
    # `items` is some funny StopIteration-raising generator. There's no point
    # in swallowing this exception.
    next(cur)
    next(nex)
    next(nex)
    return zip(prev, cur, nex)

def get_combinator_sql(self, combinator, all):
        features = self.connection.features
        compilers = [
            query.get_compiler(self.using, self.connection)
            for query in self.query.combined_queries
        ]
        if not features.supports_slicing_ordering_in_compound:
            for query, compiler in zip(self.query.combined_queries, compilers):
                if query.low_mark or query.high_mark:
                    raise DatabaseError('LIMIT/OFFSET not allowed in subqueries of compound statements.')
                if compiler.get_order_by():
                    raise DatabaseError('ORDER BY not allowed in subqueries of compound statements.')
        parts = (compiler.as_sql() for compiler in compilers)
        combinator_sql = self.connection.ops.set_operators[combinator]
        if all and combinator == 'union':
            combinator_sql += ' ALL'
        braces = '({})' if features.supports_slicing_ordering_in_compound else '{}'
        sql_parts, args_parts = zip(*((braces.format(sql), args) for sql, args in parts))
        result = [' {} '.format(combinator_sql).join(sql_parts)]
        params = []
        for part in args_parts:
            params.extend(part)
        return result, params

def get_combinator_sql(self, combinator, all):
        features = self.connection.features
        compilers = [
            query.get_compiler(self.using, self.connection)
            for query in self.query.combined_queries if not query.is_empty()
        ]
        if not features.supports_slicing_ordering_in_compound:
            for query, compiler in zip(self.query.combined_queries, compilers):
                if query.low_mark or query.high_mark:
                    raise DatabaseError('LIMIT/OFFSET not allowed in subqueries of compound statements.')
                if compiler.get_order_by():
                    raise DatabaseError('ORDER BY not allowed in subqueries of compound statements.')
        parts = (compiler.as_sql() for compiler in compilers)
        combinator_sql = self.connection.ops.set_operators[combinator]
        if all and combinator == 'union':
            combinator_sql += ' ALL'
        braces = '({})' if features.supports_slicing_ordering_in_compound else '{}'
        sql_parts, args_parts = zip(*((braces.format(sql), args) for sql, args in parts))
        result = [' {} '.format(combinator_sql).join(sql_parts)]
        params = []
        for part in args_parts:
            params.extend(part)
        return result, params

def assemble_as_sql(self, fields, value_rows):
        """
        Take a sequence of N fields and a sequence of M rows of values,
        generate placeholder SQL and parameters for each field and value, and
        return a pair containing:
         * a sequence of M rows of N SQL placeholder strings, and
         * a sequence of M rows of corresponding parameter values.

        Each placeholder string may contain any number of '%s' interpolation
        strings, and each parameter row will contain exactly as many params
        as the total number of '%s's in the corresponding placeholder row.
        """
        if not value_rows:
            return [], []

        # list of (sql, [params]) tuples for each object to be saved
        # Shape: [n_objs][n_fields][2]
        rows_of_fields_as_sql = (
            (self.field_as_sql(field, v) for field, v in zip(fields, row))
            for row in value_rows
        )

        # tuple like ([sqls], [[params]s]) for each object to be saved
        # Shape: [n_objs][2][n_fields]
        sql_and_param_pair_rows = (zip(*row) for row in rows_of_fields_as_sql)

        # Extract separate lists for placeholders and params.
        # Each of these has shape [n_objs][n_fields]
        placeholder_rows, param_rows = zip(*sql_and_param_pair_rows)

        # Params for each field are still lists, and need to be flattened.
        param_rows = [[p for ps in row for p in ps] for row in param_rows]

        return placeholder_rows, param_rows

def from_db(cls, db, field_names, values):
        if cls._deferred:
            new = cls(**dict(zip(field_names, values)))
        else:
            new = cls(*values)
        new._state.adding = False
        new._state.db = db
        return new

def build_aggregate(self, queryset, compiler):
        agg = super(ManyToOneConstructor, self).build_aggregate(queryset, compiler)

        # Any ordering needs to be plucked from the query set and added into the JSONAgg that we will be build
        # because SQL
        kwargs = {}
        if queryset.ordered:
            kwargs['order_by'] = next(zip(*queryset.query.get_compiler(connection=compiler.connection).get_order_by()))
        queryset.query.clear_ordering(True)

        # many_to_one is a bit of a misnomer, the field we have is the "one" side
        return JSONAgg(agg, **kwargs)

def _salt_cipher_secret(secret):
    """
    Given a secret (assumed to be a string of CSRF_ALLOWED_CHARS), generate a
    token by adding a salt and using it to encrypt the secret.
    """
    salt = _get_new_csrf_string()
    chars = CSRF_ALLOWED_CHARS
    pairs = zip((chars.index(x) for x in secret), (chars.index(x) for x in salt))
    cipher = ''.join(chars[(x + y) % len(chars)] for x, y in pairs)
    return salt + cipher

def _unsalt_cipher_token(token):
    """
    Given a token (assumed to be a string of CSRF_ALLOWED_CHARS, of length
    CSRF_TOKEN_LENGTH, and that its first half is a salt), use it to decrypt
    the second half to produce the original secret.
    """
    salt = token[:CSRF_SECRET_LENGTH]
    token = token[CSRF_SECRET_LENGTH:]
    chars = CSRF_ALLOWED_CHARS
    pairs = zip((chars.index(x) for x in token), (chars.index(x) for x in salt))
    secret = ''.join(chars[x - y] for x, y in pairs)  # Note negative values are ok
    return secret

def assemble_as_sql(self, fields, value_rows):
        """
        Take a sequence of N fields and a sequence of M rows of values,
        generate placeholder SQL and parameters for each field and value, and
        return a pair containing:
         * a sequence of M rows of N SQL placeholder strings, and
         * a sequence of M rows of corresponding parameter values.

        Each placeholder string may contain any number of '%s' interpolation
        strings, and each parameter row will contain exactly as many params
        as the total number of '%s's in the corresponding placeholder row.
        """
        if not value_rows:
            return [], []

        # list of (sql, [params]) tuples for each object to be saved
        # Shape: [n_objs][n_fields][2]
        rows_of_fields_as_sql = (
            (self.field_as_sql(field, v) for field, v in zip(fields, row))
            for row in value_rows
        )

        # tuple like ([sqls], [[params]s]) for each object to be saved
        # Shape: [n_objs][2][n_fields]
        sql_and_param_pair_rows = (zip(*row) for row in rows_of_fields_as_sql)

        # Extract separate lists for placeholders and params.
        # Each of these has shape [n_objs][n_fields]
        placeholder_rows, param_rows = zip(*sql_and_param_pair_rows)

        # Params for each field are still lists, and need to be flattened.
        param_rows = [[p for ps in row for p in ps] for row in param_rows]

        return placeholder_rows, param_rows

def _salt_cipher_secret(secret):
    """
    Given a secret (assumed to be a string of CSRF_ALLOWED_CHARS), generate a
    token by adding a salt and using it to encrypt the secret.
    """
    salt = _get_new_csrf_string()
    chars = CSRF_ALLOWED_CHARS
    pairs = zip((chars.index(x) for x in secret), (chars.index(x) for x in salt))
    cipher = ''.join(chars[(x + y) % len(chars)] for x, y in pairs)
    return salt + cipher

def _unsalt_cipher_token(token):
    """
    Given a token (assumed to be a string of CSRF_ALLOWED_CHARS, of length
    CSRF_TOKEN_LENGTH, and that its first half is a salt), use it to decrypt
    the second half to produce the original secret.
    """
    salt = token[:CSRF_SECRET_LENGTH]
    token = token[CSRF_SECRET_LENGTH:]
    chars = CSRF_ALLOWED_CHARS
    pairs = zip((chars.index(x) for x in token), (chars.index(x) for x in salt))
    secret = ''.join(chars[x - y] for x, y in pairs)  # Note negative values are ok
    return secret

def assemble_as_sql(self, fields, value_rows):
        """
        Take a sequence of N fields and a sequence of M rows of values,
        generate placeholder SQL and parameters for each field and value, and
        return a pair containing:
         * a sequence of M rows of N SQL placeholder strings, and
         * a sequence of M rows of corresponding parameter values.

        Each placeholder string may contain any number of '%s' interpolation
        strings, and each parameter row will contain exactly as many params
        as the total number of '%s's in the corresponding placeholder row.
        """
        if not value_rows:
            return [], []

        # list of (sql, [params]) tuples for each object to be saved
        # Shape: [n_objs][n_fields][2]
        rows_of_fields_as_sql = (
            (self.field_as_sql(field, v) for field, v in zip(fields, row))
            for row in value_rows
        )

        # tuple like ([sqls], [[params]s]) for each object to be saved
        # Shape: [n_objs][2][n_fields]
        sql_and_param_pair_rows = (zip(*row) for row in rows_of_fields_as_sql)

        # Extract separate lists for placeholders and params.
        # Each of these has shape [n_objs][n_fields]
        placeholder_rows, param_rows = zip(*sql_and_param_pair_rows)

        # Params for each field are still lists, and need to be flattened.
        param_rows = [[p for ps in row for p in ps] for row in param_rows]

        return placeholder_rows, param_rows

def assemble_as_sql(self, fields, value_rows):
        """
        Take a sequence of N fields and a sequence of M rows of values,
        generate placeholder SQL and parameters for each field and value, and
        return a pair containing:
         * a sequence of M rows of N SQL placeholder strings, and
         * a sequence of M rows of corresponding parameter values.

        Each placeholder string may contain any number of '%s' interpolation
        strings, and each parameter row will contain exactly as many params
        as the total number of '%s's in the corresponding placeholder row.
        """
        if not value_rows:
            return [], []

        # list of (sql, [params]) tuples for each object to be saved
        # Shape: [n_objs][n_fields][2]
        rows_of_fields_as_sql = (
            (self.field_as_sql(field, v) for field, v in zip(fields, row))
            for row in value_rows
        )

        # tuple like ([sqls], [[params]s]) for each object to be saved
        # Shape: [n_objs][2][n_fields]
        sql_and_param_pair_rows = (zip(*row) for row in rows_of_fields_as_sql)

        # Extract separate lists for placeholders and params.
        # Each of these has shape [n_objs][n_fields]
        placeholder_rows, param_rows = zip(*sql_and_param_pair_rows)

        # Params for each field are still lists, and need to be flattened.
        param_rows = [[p for ps in row for p in ps] for row in param_rows]

        return placeholder_rows, param_rows

def from_db(cls, db, field_names, values):
        if cls._deferred:
            new = cls(**dict(zip(field_names, values)))
        else:
            new = cls(*values)
        new._state.adding = False
        new._state.db = db
        return new

def resolve_columns(self, row, fields=()):
        """
        This routine is necessary so that distances and geometries returned
        from extra selection SQL get resolved appropriately into Python
        objects.
        """
        values = []
        aliases = list(self.query.extra_select)

        # Have to set a starting row number offset that is used for
        # determining the correct starting row index -- needed for
        # doing pagination with Oracle.
        rn_offset = 0
        if self.connection.ops.oracle:
            if self.query.high_mark is not None or self.query.low_mark: rn_offset = 1
        index_start = rn_offset + len(aliases)

        # Converting any extra selection values (e.g., geometries and
        # distance objects added by GeoQuerySet methods).
        values = [self.query.convert_values(v,
                               self.query.extra_select_fields.get(a, None),
                               self.connection)
                  for v, a in zip(row[rn_offset:index_start], aliases)]
        if self.connection.ops.oracle or getattr(self.query, 'geo_values', False):
            # We resolve the rest of the columns if we're on Oracle or if
            # the `geo_values` attribute is defined.
            for value, field in zip_longest(row[index_start:], fields):
                values.append(self.query.convert_values(value, field, self.connection))
        else:
            values.extend(row[index_start:])
        return tuple(values)

    #### Routines unique to GeoQuery ####

def assemble_as_sql(self, fields, value_rows):
        """
        Take a sequence of N fields and a sequence of M rows of values,
        generate placeholder SQL and parameters for each field and value, and
        return a pair containing:
         * a sequence of M rows of N SQL placeholder strings, and
         * a sequence of M rows of corresponding parameter values.

        Each placeholder string may contain any number of '%s' interpolation
        strings, and each parameter row will contain exactly as many params
        as the total number of '%s's in the corresponding placeholder row.
        """
        if not value_rows:
            return [], []

        # list of (sql, [params]) tuples for each object to be saved
        # Shape: [n_objs][n_fields][2]
        rows_of_fields_as_sql = (
            (self.field_as_sql(field, v) for field, v in zip(fields, row))
            for row in value_rows
        )

        # tuple like ([sqls], [[params]s]) for each object to be saved
        # Shape: [n_objs][2][n_fields]
        sql_and_param_pair_rows = (zip(*row) for row in rows_of_fields_as_sql)

        # Extract separate lists for placeholders and params.
        # Each of these has shape [n_objs][n_fields]
        placeholder_rows, param_rows = zip(*sql_and_param_pair_rows)

        # Params for each field are still lists, and need to be flattened.
        param_rows = [[p for ps in row for p in ps] for row in param_rows]

        return placeholder_rows, param_rows

def from_db(cls, db, field_names, values):
        if cls._deferred:
            new = cls(**dict(zip(field_names, values)))
        else:
            new = cls(*values)
        new._state.adding = False
        new._state.db = db
        return new

def _salt_cipher_secret(secret):
    """
    Given a secret (assumed to be a string of CSRF_ALLOWED_CHARS), generate a
    token by adding a salt and using it to encrypt the secret.
    """
    salt = _get_new_csrf_string()
    chars = CSRF_ALLOWED_CHARS
    pairs = zip((chars.index(x) for x in secret), (chars.index(x) for x in salt))
    cipher = ''.join(chars[(x + y) % len(chars)] for x, y in pairs)
    return salt + cipher

def _unsalt_cipher_token(token):
    """
    Given a token (assumed to be a string of CSRF_ALLOWED_CHARS, of length
    CSRF_TOKEN_LENGTH, and that its first half is a salt), use it to decrypt
    the second half to produce the original secret.
    """
    salt = token[:CSRF_SECRET_LENGTH]
    token = token[CSRF_SECRET_LENGTH:]
    chars = CSRF_ALLOWED_CHARS
    pairs = zip((chars.index(x) for x in token), (chars.index(x) for x in salt))
    secret = ''.join(chars[x - y] for x, y in pairs)  # Note negative values are ok
    return secret

def assemble_as_sql(self, fields, value_rows):
        """
        Take a sequence of N fields and a sequence of M rows of values,
        generate placeholder SQL and parameters for each field and value, and
        return a pair containing:
         * a sequence of M rows of N SQL placeholder strings, and
         * a sequence of M rows of corresponding parameter values.

        Each placeholder string may contain any number of '%s' interpolation
        strings, and each parameter row will contain exactly as many params
        as the total number of '%s's in the corresponding placeholder row.
        """
        if not value_rows:
            return [], []

        # list of (sql, [params]) tuples for each object to be saved
        # Shape: [n_objs][n_fields][2]
        rows_of_fields_as_sql = (
            (self.field_as_sql(field, v) for field, v in zip(fields, row))
            for row in value_rows
        )

        # tuple like ([sqls], [[params]s]) for each object to be saved
        # Shape: [n_objs][2][n_fields]
        sql_and_param_pair_rows = (zip(*row) for row in rows_of_fields_as_sql)

        # Extract separate lists for placeholders and params.
        # Each of these has shape [n_objs][n_fields]
        placeholder_rows, param_rows = zip(*sql_and_param_pair_rows)

        # Params for each field are still lists, and need to be flattened.
        param_rows = [[p for ps in row for p in ps] for row in param_rows]

        return placeholder_rows, param_rows

def from_db(cls, db, field_names, values):
        if cls._deferred:
            new = cls(**dict(zip(field_names, values)))
        else:
            new = cls(*values)
        new._state.adding = False
        new._state.db = db
        return new

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            value_rows = [
                [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
                for obj in self.query.objs
            ]
        else:
            # An empty object.
            value_rows = [[self.connection.ops.pk_default_value()] for _ in self.query.objs]
            fields = [None]

        # Currently the backends just accept values when generating bulk
        # queries and generate their own placeholders. Doing that isn't
        # necessary and it should be possible to use placeholders and
        # expressions in bulk inserts too.
        can_bulk = (not self.return_id and self.connection.features.has_bulk_insert)

        placeholder_rows, param_rows = self.assemble_as_sql(fields, value_rows)

        if self.return_id and self.connection.features.can_return_id_from_insert:
            params = param_rows[0]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            result.append("VALUES (%s)" % ", ".join(placeholder_rows[0]))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += r_params
            return [(" ".join(result), tuple(params))]

        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
            return [(" ".join(result), tuple(p for ps in param_rows for p in ps))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholder_rows, param_rows)
            ]

def flatten_result(source):
    """
    Turns the given source sequence into a list of reg-exp possibilities and
    their arguments. Returns a list of strings and a list of argument lists.
    Each of the two lists will be of the same length.
    """
    if source is None:
        return [''], [[]]
    if isinstance(source, Group):
        if source[1] is None:
            params = []
        else:
            params = [source[1]]
        return [source[0]], [params]
    result = ['']
    result_args = [[]]
    pos = last = 0
    for pos, elt in enumerate(source):
        if isinstance(elt, six.string_types):
            continue
        piece = ''.join(source[last:pos])
        if isinstance(elt, Group):
            piece += elt[0]
            param = elt[1]
        else:
            param = None
        last = pos + 1
        for i in range(len(result)):
            result[i] += piece
            if param:
                result_args[i].append(param)
        if isinstance(elt, (Choice, NonCapture)):
            if isinstance(elt, NonCapture):
                elt = [elt]
            inner_result, inner_args = [], []
            for item in elt:
                res, args = flatten_result(item)
                inner_result.extend(res)
                inner_args.extend(args)
            new_result = []
            new_args = []
            for item, args in zip(result, result_args):
                for i_item, i_args in zip(inner_result, inner_args):
                    new_result.append(item + i_item)
                    new_args.append(args[:] + i_args)
            result = new_result
            result_args = new_args
    if pos >= last:
        piece = ''.join(source[last:])
        for i in range(len(result)):
            result[i] += piece
    return result, result_args

def parse_nested(cls, instance, field, nested, datas):
        if field.many_to_one or field.one_to_one:
            datas = (datas, )
        ps = []

        # Fun caveat of throwing everything into JSON, it doesn't support datetimes. Everything gets sent back as iso8601 strings
        # Make a list of all fields that should be datetimes and parse them ahead of time
        dts = [i for i, f in enumerate(field.related_model._meta.concrete_fields) if isinstance(f, models.DateTimeField)]

        for data in datas or []:
            if data is None:
                ps.append(None)
                continue

            data, nested_data = data[:-len(nested) or None], data[-len(nested):]

            for i in dts:
                data[i] = util.parse_datetime(data[i])

            # from_db expects the final argument to be a tuple of fields in the order of concrete_fields
            parsed = field.related_model.from_db(instance._state.db, None, data)

            for (f, n), d in zip(nested.items(), nested_data):
                cls.parse_nested(parsed, f, n, d)

            if field.remote_field.concrete:
                setattr(parsed, field.remote_field.get_cache_name(), instance)

            ps.append(parsed)

        if (field.many_to_one or field.one_to_one) and ps:
            return setattr(instance, field.get_cache_name(), ps[0])

        if not hasattr(instance, '_prefetched_objects_cache'):
            instance._prefetched_objects_cache = {}

        if hasattr(field, 'get_accessor_name'):
            accessor_name = field.get_accessor_name()
        else:
            accessor_name = field.name

        # get_queryset() sets a bunch of attributes for us and will respect any custom managers
        instance._prefetched_objects_cache[field.name] = getattr(instance, accessor_name).get_queryset()
        instance._prefetched_objects_cache[field.name]._result_cache = ps
        instance._prefetched_objects_cache[field.name]._prefetch_done = True

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            value_rows = [
                [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
                for obj in self.query.objs
            ]
        else:
            # An empty object.
            value_rows = [[self.connection.ops.pk_default_value()] for _ in self.query.objs]
            fields = [None]

        # Currently the backends just accept values when generating bulk
        # queries and generate their own placeholders. Doing that isn't
        # necessary and it should be possible to use placeholders and
        # expressions in bulk inserts too.
        can_bulk = (not self.return_id and self.connection.features.has_bulk_insert)

        placeholder_rows, param_rows = self.assemble_as_sql(fields, value_rows)

        if self.return_id and self.connection.features.can_return_id_from_insert:
            if self.connection.features.can_return_ids_from_bulk_insert:
                result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
                params = param_rows
            else:
                result.append("VALUES (%s)" % ", ".join(placeholder_rows[0]))
                params = [param_rows[0]]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += [r_params]
            return [(" ".join(result), tuple(chain.from_iterable(params)))]

        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
            return [(" ".join(result), tuple(p for ps in param_rows for p in ps))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholder_rows, param_rows)
            ]

def flatten_result(source):
    """
    Turns the given source sequence into a list of reg-exp possibilities and
    their arguments. Returns a list of strings and a list of argument lists.
    Each of the two lists will be of the same length.
    """
    if source is None:
        return [''], [[]]
    if isinstance(source, Group):
        if source[1] is None:
            params = []
        else:
            params = [source[1]]
        return [source[0]], [params]
    result = ['']
    result_args = [[]]
    pos = last = 0
    for pos, elt in enumerate(source):
        if isinstance(elt, six.string_types):
            continue
        piece = ''.join(source[last:pos])
        if isinstance(elt, Group):
            piece += elt[0]
            param = elt[1]
        else:
            param = None
        last = pos + 1
        for i in range(len(result)):
            result[i] += piece
            if param:
                result_args[i].append(param)
        if isinstance(elt, (Choice, NonCapture)):
            if isinstance(elt, NonCapture):
                elt = [elt]
            inner_result, inner_args = [], []
            for item in elt:
                res, args = flatten_result(item)
                inner_result.extend(res)
                inner_args.extend(args)
            new_result = []
            new_args = []
            for item, args in zip(result, result_args):
                for i_item, i_args in zip(inner_result, inner_args):
                    new_result.append(item + i_item)
                    new_args.append(args[:] + i_args)
            result = new_result
            result_args = new_args
    if pos >= last:
        piece = ''.join(source[last:])
        for i in range(len(result)):
            result[i] += piece
    return result, result_args

def copy_plugins_to(old_plugins, to_placeholder,
                    to_language=None, parent_plugin_id=None, no_signals=False):
    """
    Copies a list of plugins to a placeholder to a language.
    """
    # TODO: Refactor this and copy_plugins to cleanly separate plugin tree/node
    # copying and remove the need for the mutating parameter old_parent_cache.
    old_parent_cache = {}
    # For subplugin copy, top-level plugin's parent must be nulled
    # before copying.
    if old_plugins:
        old_parent = old_plugins[0].parent
        for old_plugin in old_plugins:
            if old_plugin.parent == old_parent:
                old_plugin.parent = old_plugin.parent_id = None
    new_plugins = []
    for old in old_plugins:
        new_plugins.append(
            old.copy_plugin(to_placeholder, to_language or old.language,
                            old_parent_cache, no_signals))

    if new_plugins and parent_plugin_id:
        from cms.models import CMSPlugin
        parent_plugin = CMSPlugin.objects.get(pk=parent_plugin_id)
        for idx, plugin in enumerate(new_plugins):
            if plugin.parent_id is None:
                plugin.parent_id = parent_plugin_id
                # Always use update fields to avoid side-effects.
                # In this case "plugin" has invalid values for internal fields
                # like numchild.
                # The invalid value is only in memory because the instance
                # was never updated.
                plugin.save(update_fields=['parent'])
                new_plugins[idx] = plugin.move(parent_plugin, pos="last-child")

    plugins_ziplist = list(zip(new_plugins, old_plugins))

    # this magic is needed for advanced plugins like Text Plugins that can have
    # nested plugins and need to update their content based on the new plugins.
    for new_plugin, old_plugin in plugins_ziplist:
        new_instance = new_plugin.get_plugin_instance()[0]
        if new_instance:
            new_instance._no_reorder = True
            new_instance.post_copy(old_plugin, plugins_ziplist)

    # returns information about originals and copies
    return plugins_ziplist

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            value_rows = [
                [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
                for obj in self.query.objs
            ]
        else:
            # An empty object.
            value_rows = [[self.connection.ops.pk_default_value()] for _ in self.query.objs]
            fields = [None]

        # Currently the backends just accept values when generating bulk
        # queries and generate their own placeholders. Doing that isn't
        # necessary and it should be possible to use placeholders and
        # expressions in bulk inserts too.
        can_bulk = (not self.return_id and self.connection.features.has_bulk_insert)

        placeholder_rows, param_rows = self.assemble_as_sql(fields, value_rows)

        if self.return_id and self.connection.features.can_return_id_from_insert:
            if self.connection.features.can_return_ids_from_bulk_insert:
                result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
                params = param_rows
            else:
                result.append("VALUES (%s)" % ", ".join(placeholder_rows[0]))
                params = [param_rows[0]]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += [r_params]
            return [(" ".join(result), tuple(chain.from_iterable(params)))]

        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
            return [(" ".join(result), tuple(p for ps in param_rows for p in ps))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholder_rows, param_rows)
            ]

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            value_rows = [
                [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
                for obj in self.query.objs
            ]
        else:
            # An empty object.
            value_rows = [[self.connection.ops.pk_default_value()] for _ in self.query.objs]
            fields = [None]

        # Currently the backends just accept values when generating bulk
        # queries and generate their own placeholders. Doing that isn't
        # necessary and it should be possible to use placeholders and
        # expressions in bulk inserts too.
        can_bulk = (not self.return_id and self.connection.features.has_bulk_insert)

        placeholder_rows, param_rows = self.assemble_as_sql(fields, value_rows)

        if self.return_id and self.connection.features.can_return_id_from_insert:
            params = param_rows[0]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            result.append("VALUES (%s)" % ", ".join(placeholder_rows[0]))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += r_params
            return [(" ".join(result), tuple(params))]

        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
            return [(" ".join(result), tuple(p for ps in param_rows for p in ps))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholder_rows, param_rows)
            ]

def flatten_result(source):
    """
    Turns the given source sequence into a list of reg-exp possibilities and
    their arguments. Returns a list of strings and a list of argument lists.
    Each of the two lists will be of the same length.
    """
    if source is None:
        return [''], [[]]
    if isinstance(source, Group):
        if source[1] is None:
            params = []
        else:
            params = [source[1]]
        return [source[0]], [params]
    result = ['']
    result_args = [[]]
    pos = last = 0
    for pos, elt in enumerate(source):
        if isinstance(elt, six.string_types):
            continue
        piece = ''.join(source[last:pos])
        if isinstance(elt, Group):
            piece += elt[0]
            param = elt[1]
        else:
            param = None
        last = pos + 1
        for i in range(len(result)):
            result[i] += piece
            if param:
                result_args[i].append(param)
        if isinstance(elt, (Choice, NonCapture)):
            if isinstance(elt, NonCapture):
                elt = [elt]
            inner_result, inner_args = [], []
            for item in elt:
                res, args = flatten_result(item)
                inner_result.extend(res)
                inner_args.extend(args)
            new_result = []
            new_args = []
            for item, args in zip(result, result_args):
                for i_item, i_args in zip(inner_result, inner_args):
                    new_result.append(item + i_item)
                    new_args.append(args[:] + i_args)
            result = new_result
            result_args = new_args
    if pos >= last:
        piece = ''.join(source[last:])
        for i in range(len(result)):
            result[i] += piece
    return result, result_args

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            value_rows = [
                [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
                for obj in self.query.objs
            ]
        else:
            # An empty object.
            value_rows = [[self.connection.ops.pk_default_value()] for _ in self.query.objs]
            fields = [None]

        # Currently the backends just accept values when generating bulk
        # queries and generate their own placeholders. Doing that isn't
        # necessary and it should be possible to use placeholders and
        # expressions in bulk inserts too.
        can_bulk = (not self.return_id and self.connection.features.has_bulk_insert)

        placeholder_rows, param_rows = self.assemble_as_sql(fields, value_rows)

        if self.return_id and self.connection.features.can_return_id_from_insert:
            params = param_rows[0]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            result.append("VALUES (%s)" % ", ".join(placeholder_rows[0]))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += r_params
            return [(" ".join(result), tuple(params))]

        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
            return [(" ".join(result), tuple(p for ps in param_rows for p in ps))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholder_rows, param_rows)
            ]

def flatten_result(source):
    """
    Turns the given source sequence into a list of reg-exp possibilities and
    their arguments. Returns a list of strings and a list of argument lists.
    Each of the two lists will be of the same length.
    """
    if source is None:
        return [''], [[]]
    if isinstance(source, Group):
        if source[1] is None:
            params = []
        else:
            params = [source[1]]
        return [source[0]], [params]
    result = ['']
    result_args = [[]]
    pos = last = 0
    for pos, elt in enumerate(source):
        if isinstance(elt, six.string_types):
            continue
        piece = ''.join(source[last:pos])
        if isinstance(elt, Group):
            piece += elt[0]
            param = elt[1]
        else:
            param = None
        last = pos + 1
        for i in range(len(result)):
            result[i] += piece
            if param:
                result_args[i].append(param)
        if isinstance(elt, (Choice, NonCapture)):
            if isinstance(elt, NonCapture):
                elt = [elt]
            inner_result, inner_args = [], []
            for item in elt:
                res, args = flatten_result(item)
                inner_result.extend(res)
                inner_args.extend(args)
            new_result = []
            new_args = []
            for item, args in zip(result, result_args):
                for i_item, i_args in zip(inner_result, inner_args):
                    new_result.append(item + i_item)
                    new_args.append(args[:] + i_args)
            result = new_result
            result_args = new_args
    if pos >= last:
        piece = ''.join(source[last:])
        for i in range(len(result)):
            result[i] += piece
    return result, result_args

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            value_rows = [
                [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields]
                for obj in self.query.objs
            ]
        else:
            # An empty object.
            value_rows = [[self.connection.ops.pk_default_value()] for _ in self.query.objs]
            fields = [None]

        # Currently the backends just accept values when generating bulk
        # queries and generate their own placeholders. Doing that isn't
        # necessary and it should be possible to use placeholders and
        # expressions in bulk inserts too.
        can_bulk = (not self.return_id and self.connection.features.has_bulk_insert)

        placeholder_rows, param_rows = self.assemble_as_sql(fields, value_rows)

        if self.return_id and self.connection.features.can_return_id_from_insert:
            if self.connection.features.can_return_ids_from_bulk_insert:
                result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
                params = param_rows
            else:
                result.append("VALUES (%s)" % ", ".join(placeholder_rows[0]))
                params = [param_rows[0]]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += [r_params]
            return [(" ".join(result), tuple(chain.from_iterable(params)))]

        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, placeholder_rows))
            return [(" ".join(result), tuple(p for ps in param_rows for p in ps))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholder_rows, param_rows)
            ]

def as_sql(self):
        # We don't need quote_name_unless_alias() here, since these are all
        # going to be column names (so we can avoid the extra overhead).
        qn = self.connection.ops.quote_name
        opts = self.query.get_meta()
        result = ['INSERT INTO %s' % qn(opts.db_table)]

        has_fields = bool(self.query.fields)
        fields = self.query.fields if has_fields else [opts.pk]
        result.append('(%s)' % ', '.join(qn(f.column) for f in fields))

        if has_fields:
            params = values = [
                [
                    f.get_db_prep_save(
                        getattr(obj, f.attname) if self.query.raw else f.pre_save(obj, True),
                        connection=self.connection
                    ) for f in fields
                ]
                for obj in self.query.objs
            ]
        else:
            values = [[self.connection.ops.pk_default_value()] for obj in self.query.objs]
            params = [[]]
            fields = [None]
        can_bulk = (not any(hasattr(field, "get_placeholder") for field in fields) and
            not self.return_id and self.connection.features.has_bulk_insert)

        if can_bulk:
            placeholders = [["%s"] * len(fields)]
        else:
            placeholders = [
                [self.placeholder(field, v) for field, v in zip(fields, val)]
                for val in values
            ]
            # Oracle Spatial needs to remove some values due to #10888
            params = self.connection.ops.modify_insert_params(placeholders, params)
        if self.return_id and self.connection.features.can_return_id_from_insert:
            params = params[0]
            col = "%s.%s" % (qn(opts.db_table), qn(opts.pk.column))
            result.append("VALUES (%s)" % ", ".join(placeholders[0]))
            r_fmt, r_params = self.connection.ops.return_insert_id()
            # Skip empty r_fmt to allow subclasses to customize behavior for
            # 3rd party backends. Refs #19096.
            if r_fmt:
                result.append(r_fmt % col)
                params += r_params
            return [(" ".join(result), tuple(params))]
        if can_bulk:
            result.append(self.connection.ops.bulk_insert_sql(fields, len(values)))
            return [(" ".join(result), tuple(v for val in values for v in val))]
        else:
            return [
                (" ".join(result + ["VALUES (%s)" % ", ".join(p)]), vals)
                for p, vals in zip(placeholders, params)
            ]

def flatten_result(source):
    """
    Turns the given source sequence into a list of reg-exp possibilities and
    their arguments. Returns a list of strings and a list of argument lists.
    Each of the two lists will be of the same length.
    """
    if source is None:
        return [''], [[]]
    if isinstance(source, Group):
        if source[1] is None:
            params = []
        else:
            params = [source[1]]
        return [source[0]], [params]
    result = ['']
    result_args = [[]]
    pos = last = 0
    for pos, elt in enumerate(source):
        if isinstance(elt, six.string_types):
            continue
        piece = ''.join(source[last:pos])
        if isinstance(elt, Group):
            piece += elt[0]
            param = elt[1]
        else:
            param = None
        last = pos + 1
        for i in range(len(result)):
            result[i] += piece
            if param:
                result_args[i].append(param)
        if isinstance(elt, (Choice, NonCapture)):
            if isinstance(elt, NonCapture):
                elt = [elt]
            inner_result, inner_args = [], []
            for item in elt:
                res, args = flatten_result(item)
                inner_result.extend(res)
                inner_args.extend(args)
            new_result = []
            new_args = []
            for item, args in zip(result, result_args):
                for i_item, i_args in zip(inner_result, inner_args):
                    new_result.append(item + i_item)
                    new_args.append(args[:] + i_args)
            result = new_result
            result_args = new_args
    if pos >= last:
        piece = ''.join(source[last:])
        for i in range(len(result)):
            result[i] += piece
    return result, result_args