fix: Remove the hard-coded database URI in the test helper to use an env var (#865)

tests/clear_postgres_db.py

@@ -1,8 +1,19 @@
+import os
+
 from sqlalchemy import create_engine, MetaData
 
-engine = create_engine("postgresql+pg8000://memgpt:memgpt@localhost:8888/memgpt")
 
-meta = MetaData()
-meta.reflect(bind=engine)
+def main():
+    uri = os.environ.get(
+        "PGVECTOR_TEST_DB_URL",
+        "postgresql+pg8000://memgpt:memgpt@localhost:8888/memgpt",
+    )
 
-meta.drop_all(bind=engine)
+    engine = create_engine(uri)
+    meta = MetaData()
+    meta.reflect(bind=engine)
+    meta.drop_all(bind=engine)
+
+
+if __name__ == "__main__":
+    main()