implement object relation store with sqlite

src/knowledge/object/relation.py

@@ -1,16 +1,64 @@
 # define a relation store class
+import sqlite3
+import os
+import logging
 from .object_id import ObjectID
 
 
 class ObjectRelationStore:
     def __init__(self, root_dir: str):
-        pass
+        if not os.path.exists(root_dir):
+            os.makedirs(root_dir)
+        file = os.path.join(root_dir, "relationships.db")
+        logging.info(f"will init chunk tracker, db={file}")
+
+        self.conn = sqlite3.connect(file)
+        self.cursor = self.conn.cursor()
+        self.cursor.execute(
+            """
+            CREATE TABLE IF NOT EXISTS relationships (
+                id TEXT NOT NULL,
+                parent TEXT NOT NULL,
+                PRIMARY KEY(id, parent)
+            )
+        """
+        )
+        self.conn.commit()
 
     def add_relation(self, object: ObjectID, parent: ObjectID):
-        pass
+        self.cursor.execute(
+            """
+            INSERT INTO relationships (id, parent)
+            VALUES (?, ?, ?, ?, ?)
+        """,
+            (
+                str(object),
+                str(parent),
+            ),
+        )
+        self.conn.commit()
 
     def get_related_objects(self, object: ObjectID) -> [ObjectID]:
-        pass
+        parents = []
+        cur = object
+        while True:
+            self.cursor.execute(
+                """
+                SELECT id, parent FROM relationships WHERE id = ?
+            """,
+                (str(cur),),
+            )
+            parent = self.cursor.fetchone()
+            if parent is None:
+                break
+            parents.append(parent)
+            cur = parent
 
     def delete_relation(self, object_id: ObjectID) -> [ObjectID]:
-        pass
+        self.cursor.execute(
+            """
+            DELETE FROM relationships WHERE id = ?
+        """,
+            (str(object_id),),
+        )
+        self.conn.commit()