From 366285a4c3754a5db3b44797269136d92192da7e Mon Sep 17 00:00:00 2001
From: Jiangzhou He <hejiangzhou@gmail.com>
Date: Tue, 23 Sep 2025 15:46:13 -0700
Subject: [PATCH] feat(lancedb): expose a shared connection for query

---
 python/cocoindex/targets/lancedb.py | 46 ++++++++++++++++++++---------
 1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/python/cocoindex/targets/lancedb.py b/python/cocoindex/targets/lancedb.py
index c6fe214b..e51a0a1d 100644
--- a/python/cocoindex/targets/lancedb.py
+++ b/python/cocoindex/targets/lancedb.py
@@ -1,6 +1,9 @@
-import datetime
 import dataclasses
+import threading
 import uuid
+import weakref
+import datetime
+
 from typing import Any
 
 import lancedb  # type: ignore
@@ -21,7 +24,6 @@
 
 @dataclasses.dataclass
 class DatabaseOptions:
-    read_consistency_interval: datetime.timedelta | None = None
     storage_options: dict[str, Any] | None = None
 
 
@@ -45,17 +47,33 @@ class _TableKey:
     table_name: str
 
 
-async def _open_db(
-    db_uri: str, db_options: DatabaseOptions | None
-) -> lancedb.AsyncConnection:
-    db_options = db_options or DatabaseOptions()
+_DbConnectionsLock = threading.Lock()
+_DbConnections: weakref.WeakValueDictionary[str, lancedb.AsyncConnection] = (
+    weakref.WeakValueDictionary()
+)
+
 
-    # TODO: reuse cached connections
-    return await lancedb.connect_async(
-        db_uri,
-        read_consistency_interval=db_options.read_consistency_interval,
-        storage_options=db_options.storage_options,
-    )
+async def connect_async(
+    db_uri: str,
+    *,
+    db_options: DatabaseOptions | None = None,
+    read_consistency_interval: datetime.timedelta | None = None,
+) -> lancedb.AsyncConnection:
+    """
+    Helper function to connect to a LanceDB database.
+    It will reuse the connection if it already exists.
+    The connection will be shared with the target used by cocoindex, so it achieves strong consistency.
+    """
+    with _DbConnectionsLock:
+        conn = _DbConnections.get(db_uri)
+        if conn is None:
+            db_options = db_options or DatabaseOptions()
+            _DbConnections[db_uri] = conn = await lancedb.connect_async(
+                db_uri,
+                storage_options=db_options.storage_options,
+                read_consistency_interval=read_consistency_interval,
+            )
+        return conn
 
 
 def make_pa_schema(
@@ -262,7 +280,7 @@ async def apply_setup_change(
         latest_state = current or previous
         if not latest_state:
             return
-        db_conn = await _open_db(key.db_uri, latest_state.db_options)
+        db_conn = await connect_async(key.db_uri, db_options=latest_state.db_options)
 
         reuse_table = (
             previous is not None
@@ -291,7 +309,7 @@ async def prepare(
         spec: LanceDB,
         setup_state: _State,
     ) -> _MutateContext:
-        db_conn = await _open_db(spec.db_uri, spec.db_options)
+        db_conn = await connect_async(spec.db_uri, db_options=spec.db_options)
         table = await db_conn.open_table(spec.table_name)
         return _MutateContext(
             table=table,