Use index for ProxyBlock.references

CHANGELOG.md

@@ -4,6 +4,7 @@
 * Stop generating debian metapackages and packages with the version attached
   to the package name. Updates in the apt-repository now support multiple
   package versions and upgrading `gtirb` with `apt-get upgrade`.
+* Fix performance issue when checking references of ProxyBlocks in Python API.
 
 # 2.0.0
 

python/gtirb/block.py

@@ -21,11 +21,22 @@ class Block(Node):
     of Block.
     """
 
+    @property
+    def module(self) -> typing.Optional["Module"]:
+        """Get the module this node ultimately belongs to."""
+
+        raise NotImplementedError  # pragma: no cover
+
     @property
     def references(self) -> typing.Iterator["Symbol"]:
         """Get all the symbols that refer to this block."""
 
-        raise NotImplementedError  # pragma: no cover
+        if not self.module:
+            return
+
+        symbol_set = self.module._symbol_referent_index.get(self)
+        if symbol_set:
+            yield from symbol_set
 
     def _add_to_uuid_cache(self, cache: typing.Dict[UUID, Node]) -> None:
         """Update the UUID cache when this node is added."""
@@ -117,15 +128,6 @@ def address(self) -> typing.Optional[int]:
             return None
         return self.byte_interval.address + self.offset
 
-    @property
-    def references(self) -> typing.Iterator["Symbol"]:
-        if not self.module:
-            return
-
-        symbol_set = self.module._symbol_referent_index.get(self)
-        if symbol_set:
-            yield from symbol_set
-
     @property
     def section(self) -> typing.Optional["Section"]:
         """Get the section this node ultimately belongs to."""
@@ -403,12 +405,6 @@ def module(self, value: typing.Optional["Module"]) -> None:
         if value is not None:
             value.proxies.add(self)
 
-    @property
-    def references(self) -> typing.Iterator["Symbol"]:
-        if self.module is None:
-            return iter(())
-        return (s for s in self.module.symbols if s.referent == self)
-
     @property
     def incoming_edges(self) -> typing.Iterator["Edge"]:
         if self.ir is None: