Fix process fork support for Python API

tools/python_api/src_py/connection.py

@@ -33,8 +33,23 @@ def __init__(self, database, num_threads=0):
         """
 
         self.database = database
-        database.init_database()
-        self._connection = _kuzu.Connection(database._database, num_threads)
+        self.num_threads = num_threads
+        self._connection = None
+        self.init_connection()
+
+    def __getstate__(self):
+        state = {
+            "database": self.database,
+            "num_threads": self.num_threads,
+            "_connection": None
+        }
+        return state
+
+    def init_connection(self):
+        self.database.init_database()
+        if self._connection is None:
+            self._connection = _kuzu.Connection(
+                self.database._database, self.num_threads)
 
     def set_max_threads_for_exec(self, num_threads):
         """
@@ -45,7 +60,7 @@ def set_max_threads_for_exec(self, num_threads):
         num_threads : int
             Maximum number of threads to use for executing queries.
         """
-
+        self.init_connection()
         self._connection.set_max_threads_for_exec(num_threads)
 
     def execute(self, query, parameters=[]):
@@ -66,7 +81,7 @@ def execute(self, query, parameters=[]):
         QueryResult
             Query result.
         """
-
+        self.init_connection()
         prepared_statement = self.prepare(
             query) if type(query) == str else query
         return QueryResult(self,
@@ -96,6 +111,7 @@ def _get_node_property_names(self, table_name):
         PRIMARY_KEY_SYMBOL = "(PRIMARY KEY)"
         LIST_START_SYMBOL = "["
         LIST_END_SYMBOL = "]"
+        self.init_connection()
         result_str = self._connection.get_node_property_names(
             table_name)
         results = {}
@@ -136,6 +152,7 @@ def _get_node_property_names(self, table_name):
 
     def _get_node_table_names(self):
         results = []
+        self.init_connection()
         result_str = self._connection.get_node_table_names()
         for (i, line) in enumerate(result_str.splitlines()):
             # ignore first line
@@ -149,6 +166,7 @@ def _get_node_table_names(self):
 
     def _get_rel_table_names(self):
         results = []
+        self.init_connection()
         result_str = self._connection.get_rel_table_names()
         for i, line in enumerate(result_str.splitlines()):
             if i == 0:
@@ -178,5 +196,5 @@ def set_query_timeout(self, timeout_in_ms):
         timeout_in_ms : int
             query timeout value in ms for executing queries.
         """
-
+        self.init_connection()
         self._connection.set_query_timeout(timeout_in_ms)

tools/python_api/src_py/database.py

@@ -44,7 +44,7 @@ def __getstate__(self):
         state = {
             "database_path": self.database_path,
             "buffer_pool_size": self.buffer_pool_size,
-            "database": None
+            "_database": None
         }
         return state
 

tools/python_api/src_py/torch_geometric_feature_store.py

@@ -21,14 +21,6 @@ def __init__(self, db, num_threads):
             num_threads = multiprocessing.cpu_count()
         self.num_threads = num_threads
 
-    def __getstate__(self):
-        state = {
-            "connection": None,
-            "node_properties_cache": self.node_properties_cache,
-            "db": self.db.__getstate__()
-        }
-        return state
-
     def __get_connection(self):
         if not self.connection:
             self.connection = Connection(self.db, self.num_threads)

tools/python_api/src_py/torch_geometric_graph_store.py

@@ -31,14 +31,6 @@ def __init__(self, db, num_threads):
         self.num_threads = num_threads
         self.__populate_edge_attrs()
 
-    def __getstate__(self):
-        state = {
-            "connection": None,
-            "store": self.store,
-            "db": self.db.__getstate__()
-        }
-        return state
-
     @staticmethod
     def key(attr: EdgeAttr) -> Tuple:
         return (attr.edge_type, attr.layout.value, attr.is_sorted)