[Bug?] Fixing compatibility of pickles across DGL versions (#1507)

* pickle compatibility before 0.4.2

* fixing for utils.Index

* add TODOs

* fix

* fix

* more compatibility checks for DGLGraph and DGLHeteroGraph objects

* lint
Co-authored-by: Jinjing Zhou <VoVAllen@users.noreply.github.com>
Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>

python/dgl/graph.py

@@ -1050,6 +1050,15 @@ class DGLGraph(DGLBaseGraph):
         # set parent if the graph is a subgraph.
         self._parent = parent
 
+    def __setstate__(self, state):
+        # Compatibility with pickles from DGL 0.4.2-
+        if '_batch_num_nodes' not in state:
+            state = state.copy()
+            state.setdefault('_batch_num_nodes', None)
+            state.setdefault('_batch_num_edges', None)
+            state.setdefault('_parent', None)
+        self.__dict__.update(state)
+
     def _create_subgraph(self, sgi, induced_nodes, induced_edges):
         """Internal function to create a subgraph from index."""
         subg = DGLGraph(graph_data=sgi.graph,

python/dgl/graph_index.py

@@ -50,7 +50,16 @@ class GraphIndex(ObjectBase):
         """The pickle state of GraphIndex is defined as a triplet
         (number_of_nodes, readonly, src_nodes, dst_nodes)
         """
+        # Pickle compatibility check
+        # TODO: we should store a storage version number in later releases.
+        if isinstance(state, tuple) and len(state) == 5:
+            dgl_warning("The object is pickled pre-0.4.2.  Multigraph flag is ignored in 0.4.3")
+            num_nodes, _, readonly, src, dst = state
+        elif isinstance(state, tuple) and len(state) == 4:
+            # post-0.4.3.
             num_nodes, readonly, src, dst = state
+        else:
+            raise IOError('Unrecognized storage format.')
 
         self._cache = {}
         self._readonly = readonly

python/dgl/heterograph.py

@@ -275,7 +275,19 @@ class DGLHeteroGraph(object):
         return self._graph, self._ntypes, self._etypes, self._node_frames, self._edge_frames
 
     def __setstate__(self, state):
+        # Compatibility check
+        # TODO: version the storage
+        if isinstance(state, tuple) and len(state) == 5:
+            # DGL 0.4.3+
             self._init(*state)
+        elif isinstance(state, dict):
+            # DGL 0.4.2-
+            dgl_warning("The object is pickled with DGL version 0.4.2-.  "
+                        "Some of the original attributes are ignored.")
+            self._init(state['_graph'], state['_ntypes'], state['_etypes'], state['_node_frames'],
+                       state['_edge_frames'])
+        else:
+            raise IOError("Unrecognized pickle format.")
 
     def _get_msg_index(self, etid):
         """Internal function for getting the message index array of the given edge type id."""

python/dgl/heterograph_index.py

@@ -29,7 +29,28 @@ class HeteroGraphIndex(ObjectBase):
 
     def __setstate__(self, state):
         self._cache = {}
+
+        # Pickle compatibility check
+        # TODO: we should store a storage version number in later releases.
+        if isinstance(state, HeteroPickleStates):
+            # post-0.4.3
             self.__init_handle_by_constructor__(_CAPI_DGLHeteroUnpickle, state)
+        elif isinstance(state, tuple) and len(state) == 3:
+            # pre-0.4.2
+            metagraph, number_of_nodes, edges = state
+
+            self._cache = {}
+            # loop over etypes and recover unit graphs
+            rel_graphs = []
+            for i, edges_per_type in enumerate(edges):
+                src_ntype, dst_ntype = metagraph.find_edge(i)
+                num_src = number_of_nodes[src_ntype]
+                num_dst = number_of_nodes[dst_ntype]
+                src_id, dst_id, _ = edges_per_type
+                rel_graphs.append(create_unitgraph_from_coo(
+                    1 if src_ntype == dst_ntype else 2, num_src, num_dst, src_id, dst_id, "any"))
+            self.__init_handle_by_constructor__(
+                _CAPI_DGLHeteroCreateHeteroGraph, metagraph, rel_graphs)
 
     @property
     def metagraph(self):

python/dgl/utils.py

@@ -5,7 +5,7 @@ from collections.abc import Mapping, Iterable
 from functools import wraps
 import numpy as np
 
-from .base import DGLError
+from .base import DGLError, dgl_warning
 from . import backend as F
 from . import ndarray as nd
 
@@ -147,8 +147,17 @@ class Index(object):
             return self.tousertensor(), self.dtype
 
     def __setstate__(self, state):
+        # Pickle compatibility check
+        # TODO: we should store a storage version number in later releases.
+        if isinstance(state, tuple) and len(state) == 2:
+            # post-0.4.4
             data, self.dtype = state
             self._initialize_data(data)
+        else:
+            # pre-0.4.3
+            dgl_warning("The object is pickled before 0.4.3.  Setting dtype of graph to int64")
+            self.dtype = 'int64'
+            self._initialize_data(state)
 
     def get_items(self, index):
         """Return values at given positions of an Index