~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2008, 2009, 2010 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Repository formats using CHK inventories and groupcompress compression."""

import time

from bzrlib import (

    bzrdir,

    chk_map,

    chk_serializer,

    debug,

    errors,

    index as _mod_index,

    inventory,

    knit,

    osutils,

    pack,

    revision as _mod_revision,

    trace,

    ui,

    )

from bzrlib.btree_index import (

    BTreeGraphIndex,

    BTreeBuilder,

    )

from bzrlib.groupcompress import (

    _GCGraphIndex,

    GroupCompressVersionedFiles,

    )

from bzrlib.repofmt.pack_repo import (

    Pack,

    NewPack,

    KnitPackRepository,

    KnitPackStreamSource,

    PackRootCommitBuilder,

    RepositoryPackCollection,

    RepositoryFormatPack,

    ResumedPack,

    Packer,

    )

from bzrlib.static_tuple import StaticTuple

class GCPack(NewPack):

    def __init__(self, pack_collection, upload_suffix='', file_mode=None):

        """Create a NewPack instance.

        :param pack_collection: A PackCollection into which this is being

            inserted.

        :param upload_suffix: An optional suffix to be given to any temporary

            files created during the pack creation. e.g '.autopack'

        :param file_mode: An optional file mode to create the new files with.

        """

        # replaced from NewPack to:

        # - change inventory reference list length to 1

        # - change texts reference lists to 1

        # TODO: patch this to be parameterised

        # The relative locations of the packs are constrained, but all are

        # passed in because the caller has them, so as to avoid object churn.

        index_builder_class = pack_collection._index_builder_class

        # from brisbane-core

        if pack_collection.chk_index is not None:

            chk_index = index_builder_class(reference_lists=0)

        else:

            chk_index = None

        Pack.__init__(self,

            # Revisions: parents list, no text compression.

            index_builder_class(reference_lists=1),

            # Inventory: We want to map compression only, but currently the

            # knit code hasn't been updated enough to understand that, so we

            # have a regular 2-list index giving parents and compression

            # source.

            index_builder_class(reference_lists=1),

            # Texts: per file graph, for all fileids - so one reference list

            # and two elements in the key tuple.

            index_builder_class(reference_lists=1, key_elements=2),

            # Signatures: Just blobs to store, no compression, no parents

            # listing.

            index_builder_class(reference_lists=0),

            # CHK based storage - just blobs, no compression or parents.

            chk_index=chk_index

            )

        self._pack_collection = pack_collection

        # When we make readonly indices, we need this.

        self.index_class = pack_collection._index_class

        # where should the new pack be opened

        self.upload_transport = pack_collection._upload_transport

        # where are indices written out to

        self.index_transport = pack_collection._index_transport

        # where is the pack renamed to when it is finished?

        self.pack_transport = pack_collection._pack_transport

        # What file mode to upload the pack and indices with.

        self._file_mode = file_mode

        # tracks the content written to the .pack file.

        self._hash = osutils.md5()

        # a four-tuple with the length in bytes of the indices, once the pack

        # is finalised. (rev, inv, text, sigs)

        self.index_sizes = None

        # How much data to cache when writing packs. Note that this is not

        # synchronised with reads, because it's not in the transport layer, so

        # is not safe unless the client knows it won't be reading from the pack

        # under creation.

        self._cache_limit = 0

        # the temporary pack file name.

        self.random_name = osutils.rand_chars(20) + upload_suffix

        # when was this pack started ?

        self.start_time = time.time()

        # open an output stream for the data added to the pack.

        self.write_stream = self.upload_transport.open_write_stream(

            self.random_name, mode=self._file_mode)

        if 'pack' in debug.debug_flags:

            trace.mutter('%s: create_pack: pack stream open: %s%s t+%6.3fs',

                time.ctime(), self.upload_transport.base, self.random_name,

                time.time() - self.start_time)

        # A list of byte sequences to be written to the new pack, and the

        # aggregate size of them.  Stored as a list rather than separate

        # variables so that the _write_data closure below can update them.

        self._buffer = [[], 0]

        # create a callable for adding data

        #

        # robertc says- this is a closure rather than a method on the object

        # so that the variables are locals, and faster than accessing object

        # members.

        def _write_data(bytes, flush=False, _buffer=self._buffer,

            _write=self.write_stream.write, _update=self._hash.update):

            _buffer[0].append(bytes)

            _buffer[1] += len(bytes)

            # buffer cap

            if _buffer[1] > self._cache_limit or flush:

                bytes = ''.join(_buffer[0])

                _write(bytes)

                _update(bytes)

                _buffer[:] = [[], 0]

        # expose this on self, for the occasion when clients want to add data.

        self._write_data = _write_data

        # a pack writer object to serialise pack records.

        self._writer = pack.ContainerWriter(self._write_data)

        self._writer.begin()

        # what state is the pack in? (open, finished, aborted)

        self._state = 'open'

        # no name until we finish writing the content

        self.name = None

    def _check_references(self):

        """Make sure our external references are present.

        Packs are allowed to have deltas whose base is not in the pack, but it

        must be present somewhere in this collection.  It is not allowed to

        have deltas based on a fallback repository.

        (See <https://bugs.launchpad.net/bzr/+bug/288751>)

        """

        # Groupcompress packs don't have any external references, arguably CHK

        # pages have external references, but we cannot 'cheaply' determine

        # them without actually walking all of the chk pages.

class ResumedGCPack(ResumedPack):

    def _check_references(self):

        """Make sure our external compression parents are present."""

        # See GCPack._check_references for why this is empty

    def _get_external_refs(self, index):

        # GC repositories don't have compression parents external to a given

        # pack file

        return set()

class GCCHKPacker(Packer):

    """This class understand what it takes to collect a GCCHK repo."""

    def __init__(self, pack_collection, packs, suffix, revision_ids=None,

                 reload_func=None):

        super(GCCHKPacker, self).__init__(pack_collection, packs, suffix,

                                          revision_ids=revision_ids,

                                          reload_func=reload_func)

        self._pack_collection = pack_collection

        # ATM, We only support this for GCCHK repositories

        if pack_collection.chk_index is None:

            raise AssertionError('pack_collection.chk_index should not be None')

        self._gather_text_refs = False

        self._chk_id_roots = []

        self._chk_p_id_roots = []

        self._text_refs = None

        # set by .pack() if self.revision_ids is not None

        self.revision_keys = None

    def _get_progress_stream(self, source_vf, keys, message, pb):

        def pb_stream():

            substream = source_vf.get_record_stream(keys, 'groupcompress', True)

            for idx, record in enumerate(substream):

                if pb is not None:

                    pb.update(message, idx + 1, len(keys))

                yield record

        return pb_stream()

    def _get_filtered_inv_stream(self, source_vf, keys, message, pb=None):

        """Filter the texts of inventories, to find the chk pages."""

        total_keys = len(keys)

        def _filtered_inv_stream():

            id_roots_set = set()

            p_id_roots_set = set()

            stream = source_vf.get_record_stream(keys, 'groupcompress', True)

            for idx, record in enumerate(stream):

                # Inventories should always be with revisions; assume success.

                bytes = record.get_bytes_as('fulltext')

                chk_inv = inventory.CHKInventory.deserialise(None, bytes,

                                                             record.key)

                if pb is not None:

                    pb.update('inv', idx, total_keys)

                key = chk_inv.id_to_entry.key()

                if key not in id_roots_set:

                    self._chk_id_roots.append(key)

                    id_roots_set.add(key)

                p_id_map = chk_inv.parent_id_basename_to_file_id

                if p_id_map is None:

                    raise AssertionError('Parent id -> file_id map not set')

                key = p_id_map.key()

                if key not in p_id_roots_set:

                    p_id_roots_set.add(key)

                    self._chk_p_id_roots.append(key)

                yield record

            # We have finished processing all of the inventory records, we

            # don't need these sets anymore

            id_roots_set.clear()

            p_id_roots_set.clear()

        return _filtered_inv_stream()

    def _get_chk_streams(self, source_vf, keys, pb=None):

        # We want to stream the keys from 'id_roots', and things they

        # reference, and then stream things from p_id_roots and things they

        # reference, and then any remaining keys that we didn't get to.

        # We also group referenced texts together, so if one root references a

        # text with prefix 'a', and another root references a node with prefix

        # 'a', we want to yield those nodes before we yield the nodes for 'b'

        # This keeps 'similar' nodes together.

        # Note: We probably actually want multiple streams here, to help the

        #       client understand that the different levels won't compress well

        #       against each other.

        #       Test the difference between using one Group per level, and

        #       using 1 Group per prefix. (so '' (root) would get a group, then

        #       all the references to search-key 'a' would get a group, etc.)

        total_keys = len(keys)

        remaining_keys = set(keys)

        counter = [0]

        if self._gather_text_refs:

            bytes_to_info = inventory.CHKInventory._bytes_to_utf8name_key

            self._text_refs = set()

        def _get_referenced_stream(root_keys, parse_leaf_nodes=False):

            cur_keys = root_keys

            while cur_keys:

                keys_by_search_prefix = {}

                remaining_keys.difference_update(cur_keys)

                next_keys = set()

                def handle_internal_node(node):

                    for prefix, value in node._items.iteritems():

                        # We don't want to request the same key twice, and we

                        # want to order it by the first time it is seen.

                        # Even further, we don't want to request a key which is

                        # not in this group of pack files (it should be in the

                        # repo, but it doesn't have to be in the group being

                        # packed.)

                        # TODO: consider how to treat externally referenced chk

                        #       pages as 'external_references' so that we

                        #       always fill them in for stacked branches

                        if value not in next_keys and value in remaining_keys:

                            keys_by_search_prefix.setdefault(prefix,

                                []).append(value)

                            next_keys.add(value)

                def handle_leaf_node(node):

                    # Store is None, because we know we have a LeafNode, and we

                    # just want its entries

                    for file_id, bytes in node.iteritems(None):

                        name_utf8, file_id, revision_id = bytes_to_info(bytes)

                        self._text_refs.add((file_id, revision_id))

                def next_stream():

                    stream = source_vf.get_record_stream(cur_keys,

                                                         'as-requested', True)

                    for record in stream:

                        if record.storage_kind == 'absent':

                            # An absent CHK record: we assume that the missing

                            # record is in a different pack - e.g. a page not

                            # altered by the commit we're packing.

                            continue

                        bytes = record.get_bytes_as('fulltext')

                        # We don't care about search_key_func for this code,

                        # because we only care about external references.

                        node = chk_map._deserialise(bytes, record.key,

                                                    search_key_func=None)

                        common_base = node._search_prefix

                        if isinstance(node, chk_map.InternalNode):

                            handle_internal_node(node)

                        elif parse_leaf_nodes:

                            handle_leaf_node(node)

                        counter[0] += 1

                        if pb is not None:

                            pb.update('chk node', counter[0], total_keys)

                        yield record

                yield next_stream()

                # Double check that we won't be emitting any keys twice

                # If we get rid of the pre-calculation of all keys, we could

                # turn this around and do

                # next_keys.difference_update(seen_keys)

                # However, we also may have references to chk pages in another

                # pack file during autopack. We filter earlier, so we should no

                # longer need to do this

                # next_keys = next_keys.intersection(remaining_keys)

                cur_keys = []

                for prefix in sorted(keys_by_search_prefix):

                    cur_keys.extend(keys_by_search_prefix.pop(prefix))

        for stream in _get_referenced_stream(self._chk_id_roots,

                                             self._gather_text_refs):

            yield stream

        del self._chk_id_roots

        # while it isn't really possible for chk_id_roots to not be in the

        # local group of packs, it is possible that the tree shape has not

        # changed recently, so we need to filter _chk_p_id_roots by the

        # available keys

        chk_p_id_roots = [key for key in self._chk_p_id_roots

                          if key in remaining_keys]

        del self._chk_p_id_roots

        for stream in _get_referenced_stream(chk_p_id_roots, False):

            yield stream

        if remaining_keys:

            trace.mutter('There were %d keys in the chk index, %d of which'

                         ' were not referenced', total_keys,

                         len(remaining_keys))

            if self.revision_ids is None:

                stream = source_vf.get_record_stream(remaining_keys,

                                                     'unordered', True)

                yield stream

    def _build_vf(self, index_name, parents, delta, for_write=False):

        """Build a VersionedFiles instance on top of this group of packs."""

        index_name = index_name + '_index'

        index_to_pack = {}

        access = knit._DirectPackAccess(index_to_pack,

                                        reload_func=self._reload_func)

        if for_write:

            # Use new_pack

            if self.new_pack is None:

                raise AssertionError('No new pack has been set')

            index = getattr(self.new_pack, index_name)

            index_to_pack[index] = self.new_pack.access_tuple()

            index.set_optimize(for_size=True)

            access.set_writer(self.new_pack._writer, index,

                              self.new_pack.access_tuple())

            add_callback = index.add_nodes

        else:

            indices = []

            for pack in self.packs:

                sub_index = getattr(pack, index_name)

                index_to_pack[sub_index] = pack.access_tuple()

                indices.append(sub_index)

            index = _mod_index.CombinedGraphIndex(indices)

            add_callback = None

        vf = GroupCompressVersionedFiles(

            _GCGraphIndex(index,

                          add_callback=add_callback,

                          parents=parents,

                          is_locked=self._pack_collection.repo.is_locked),

            access=access,

            delta=delta)

        return vf

    def _build_vfs(self, index_name, parents, delta):

        """Build the source and target VersionedFiles."""

        source_vf = self._build_vf(index_name, parents,

                                   delta, for_write=False)

        target_vf = self._build_vf(index_name, parents,

                                   delta, for_write=True)

        return source_vf, target_vf

    def _copy_stream(self, source_vf, target_vf, keys, message, vf_to_stream,

                     pb_offset):

        trace.mutter('repacking %d %s', len(keys), message)

        self.pb.update('repacking %s' % (message,), pb_offset)

        child_pb = ui.ui_factory.nested_progress_bar()

        try:

            stream = vf_to_stream(source_vf, keys, message, child_pb)

            for _ in target_vf._insert_record_stream(stream,

                                                     random_id=True,

                                                     reuse_blocks=False):

                pass

        finally:

            child_pb.finished()

    def _copy_revision_texts(self):

        source_vf, target_vf = self._build_vfs('revision', True, False)

        if not self.revision_keys:

            # We are doing a full fetch, aka 'pack'

            self.revision_keys = source_vf.keys()

        self._copy_stream(source_vf, target_vf, self.revision_keys,

                          'revisions', self._get_progress_stream, 1)

    def _copy_inventory_texts(self):

        source_vf, target_vf = self._build_vfs('inventory', True, True)

        # It is not sufficient to just use self.revision_keys, as stacked

        # repositories can have more inventories than they have revisions.

        # One alternative would be to do something with

        # get_parent_map(self.revision_keys), but that shouldn't be any faster

        # than this.

        inventory_keys = source_vf.keys()

        missing_inventories = set(self.revision_keys).difference(inventory_keys)

        if missing_inventories:

            missing_inventories = sorted(missing_inventories)

            raise ValueError('We are missing inventories for revisions: %s'

                % (missing_inventories,))

        self._copy_stream(source_vf, target_vf, inventory_keys,

                          'inventories', self._get_filtered_inv_stream, 2)

    def _copy_chk_texts(self):

        source_vf, target_vf = self._build_vfs('chk', False, False)

        # TODO: This is technically spurious... if it is a performance issue,

        #       remove it

        total_keys = source_vf.keys()

        trace.mutter('repacking chk: %d id_to_entry roots,'

                     ' %d p_id_map roots, %d total keys',

                     len(self._chk_id_roots), len(self._chk_p_id_roots),

                     len(total_keys))

        self.pb.update('repacking chk', 3)

        child_pb = ui.ui_factory.nested_progress_bar()

        try:

            for stream in self._get_chk_streams(source_vf, total_keys,

                                                pb=child_pb):

                for _ in target_vf._insert_record_stream(stream,

                                                         random_id=True,

                                                         reuse_blocks=False):

                    pass

        finally:

            child_pb.finished()

    def _copy_text_texts(self):

        source_vf, target_vf = self._build_vfs('text', True, True)

        # XXX: We don't walk the chk map to determine referenced (file_id,

        #      revision_id) keys.  We don't do it yet because you really need

        #      to filter out the ones that are present in the parents of the

        #      rev just before the ones you are copying, otherwise the filter

        #      is grabbing too many keys...

        text_keys = source_vf.keys()

        self._copy_stream(source_vf, target_vf, text_keys,

                          'texts', self._get_progress_stream, 4)

    def _copy_signature_texts(self):

        source_vf, target_vf = self._build_vfs('signature', False, False)

        signature_keys = source_vf.keys()

        signature_keys.intersection(self.revision_keys)

        self._copy_stream(source_vf, target_vf, signature_keys,

                          'signatures', self._get_progress_stream, 5)

    def _create_pack_from_packs(self):

        self.pb.update('repacking', 0, 7)

        self.new_pack = self.open_pack()

        # Is this necessary for GC ?

        self.new_pack.set_write_cache_size(1024*1024)

        self._copy_revision_texts()

        self._copy_inventory_texts()

        self._copy_chk_texts()

        self._copy_text_texts()

        self._copy_signature_texts()

        self.new_pack._check_references()

        if not self._use_pack(self.new_pack):

            self.new_pack.abort()

            return None

        self.new_pack.finish_content()

        if len(self.packs) == 1:

            old_pack = self.packs[0]

            if old_pack.name == self.new_pack._hash.hexdigest():

                # The single old pack was already optimally packed.

                trace.mutter('single pack %s was already optimally packed',

                    old_pack.name)

                self.new_pack.abort()

                return None

        self.pb.update('finishing repack', 6, 7)

        self.new_pack.finish()

        self._pack_collection.allocate(self.new_pack)

        return self.new_pack

class GCCHKReconcilePacker(GCCHKPacker):

    """A packer which regenerates indices etc as it copies.

    This is used by ``bzr reconcile`` to cause parent text pointers to be

    regenerated.

    """

    def __init__(self, *args, **kwargs):

        super(GCCHKReconcilePacker, self).__init__(*args, **kwargs)

        self._data_changed = False

        self._gather_text_refs = True

    def _copy_inventory_texts(self):

        source_vf, target_vf = self._build_vfs('inventory', True, True)

        self._copy_stream(source_vf, target_vf, self.revision_keys,

                          'inventories', self._get_filtered_inv_stream, 2)

        if source_vf.keys() != self.revision_keys:

            self._data_changed = True

    def _copy_text_texts(self):

        """generate what texts we should have and then copy."""

        source_vf, target_vf = self._build_vfs('text', True, True)

        trace.mutter('repacking %d texts', len(self._text_refs))

        self.pb.update("repacking texts", 4)

        # we have three major tasks here:

        # 1) generate the ideal index

        repo = self._pack_collection.repo

        # We want the one we just wrote, so base it on self.new_pack

        revision_vf = self._build_vf('revision', True, False, for_write=True)

        ancestor_keys = revision_vf.get_parent_map(revision_vf.keys())

        # Strip keys back into revision_ids.

        ancestors = dict((k[0], tuple([p[0] for p in parents]))

                         for k, parents in ancestor_keys.iteritems())

        del ancestor_keys

        # TODO: _generate_text_key_index should be much cheaper to generate from

        #       a chk repository, rather than the current implementation

        ideal_index = repo._generate_text_key_index(None, ancestors)

        file_id_parent_map = source_vf.get_parent_map(self._text_refs)

        # 2) generate a keys list that contains all the entries that can

        #    be used as-is, with corrected parents.

        ok_keys = []

        new_parent_keys = {} # (key, parent_keys)

        discarded_keys = []

        NULL_REVISION = _mod_revision.NULL_REVISION

        for key in self._text_refs:

            # 0 - index

            # 1 - key

            # 2 - value

            # 3 - refs

            try:

                ideal_parents = tuple(ideal_index[key])

            except KeyError:

                discarded_keys.append(key)

                self._data_changed = True

            else:

                if ideal_parents == (NULL_REVISION,):

                    ideal_parents = ()

                source_parents = file_id_parent_map[key]

                if ideal_parents == source_parents:

                    # no change needed.

                    ok_keys.append(key)

                else:

                    # We need to change the parent graph, but we don't need to

                    # re-insert the text (since we don't pun the compression

                    # parent with the parents list)

                    self._data_changed = True

                    new_parent_keys[key] = ideal_parents

        # we're finished with some data.

        del ideal_index

        del file_id_parent_map

        # 3) bulk copy the data, updating records than need it

        def _update_parents_for_texts():

            stream = source_vf.get_record_stream(self._text_refs,

                'groupcompress', False)

            for record in stream:

                if record.key in new_parent_keys:

                    record.parents = new_parent_keys[record.key]

                yield record

        target_vf.insert_record_stream(_update_parents_for_texts())

    def _use_pack(self, new_pack):

        """Override _use_pack to check for reconcile having changed content."""

        return new_pack.data_inserted() and self._data_changed

class GCRepositoryPackCollection(RepositoryPackCollection):

    pack_factory = GCPack

    resumed_pack_factory = ResumedGCPack

    def _check_new_inventories(self):

        """Detect missing inventories or chk root entries for the new revisions

        in this write group.

        :returns: list of strs, summarising any problems found.  If the list is

            empty no problems were found.

        """

        # Ensure that all revisions added in this write group have:

        #   - corresponding inventories,

        #   - chk root entries for those inventories,

        #   - and any present parent inventories have their chk root

        #     entries too.

        # And all this should be independent of any fallback repository.

        problems = []

        key_deps = self.repo.revisions._index._key_dependencies

        new_revisions_keys = key_deps.get_new_keys()

        no_fallback_inv_index = self.repo.inventories._index

        no_fallback_chk_bytes_index = self.repo.chk_bytes._index

        no_fallback_texts_index = self.repo.texts._index

        inv_parent_map = no_fallback_inv_index.get_parent_map(

            new_revisions_keys)

        # Are any inventories for corresponding to the new revisions missing?

        corresponding_invs = set(inv_parent_map)

        missing_corresponding = set(new_revisions_keys)

        missing_corresponding.difference_update(corresponding_invs)

        if missing_corresponding:

            problems.append("inventories missing for revisions %s" %

                (sorted(missing_corresponding),))

            return problems

        # Are any chk root entries missing for any inventories?  This includes

        # any present parent inventories, which may be used when calculating

        # deltas for streaming.

        all_inv_keys = set(corresponding_invs)

        for parent_inv_keys in inv_parent_map.itervalues():

            all_inv_keys.update(parent_inv_keys)

        # Filter out ghost parents.

        all_inv_keys.intersection_update(

            no_fallback_inv_index.get_parent_map(all_inv_keys))

        parent_invs_only_keys = all_inv_keys.symmetric_difference(

            corresponding_invs)

        all_missing = set()

        inv_ids = [key[-1] for key in all_inv_keys]

        parent_invs_only_ids = [key[-1] for key in parent_invs_only_keys]

        root_key_info = _build_interesting_key_sets(

            self.repo, inv_ids, parent_invs_only_ids)

        expected_chk_roots = root_key_info.all_keys()

        present_chk_roots = no_fallback_chk_bytes_index.get_parent_map(

            expected_chk_roots)

        missing_chk_roots = expected_chk_roots.difference(present_chk_roots)

        if missing_chk_roots:

            problems.append("missing referenced chk root keys: %s"

                % (sorted(missing_chk_roots),))

            # Don't bother checking any further.

            return problems

        # Find all interesting chk_bytes records, and make sure they are

        # present, as well as the text keys they reference.

        chk_bytes_no_fallbacks = self.repo.chk_bytes.without_fallbacks()

        chk_bytes_no_fallbacks._search_key_func = \

            self.repo.chk_bytes._search_key_func

        chk_diff = chk_map.iter_interesting_nodes(

            chk_bytes_no_fallbacks, root_key_info.interesting_root_keys,

            root_key_info.uninteresting_root_keys)

        bytes_to_info = inventory.CHKInventory._bytes_to_utf8name_key

        text_keys = set()

        try:

            for record in _filter_text_keys(chk_diff, text_keys, bytes_to_info):

                pass

        except errors.NoSuchRevision, e:

            # XXX: It would be nice if we could give a more precise error here.

            problems.append("missing chk node(s) for id_to_entry maps")

        chk_diff = chk_map.iter_interesting_nodes(