[doc] Document lookup.cache to full
diff --git a/docs/content/how-to/lookup-joins.md b/docs/content/how-to/lookup-joins.md
index 34973bd..79c23e1 100644
--- a/docs/content/how-to/lookup-joins.md
+++ b/docs/content/how-to/lookup-joins.md
@@ -30,6 +30,10 @@
Paimon supports lookup joins on tables with primary keys and append tables in Flink. The following example illustrates this feature.
+{{< hint warning >}}
+Release Version 0.7.0-incubating has a relatively serious bug, please alway set `lookup.cache` = `full`.
+{{< /hint >}}
+
## Prepare
First, let's create a Paimon table and update it in real-time.
