Add note for known empty partition spec issue with Redshift

Author: kbatuigas

modules/manage/pages/iceberg/iceberg-topics-aws-glue.adoc

@@ -40,10 +40,12 @@ endif::[]
 === Nested partition spec support
 
 AWS Glue does not support partitioning on nested fields. If Redpanda detects that
-the default partitioning `(hour(redpanda.timestamp))` is in use, it will instead apply an empty partition spec `()`, which means the table will not be partitioned.
+the default partitioning `(hour(redpanda.timestamp))` based on the record metadata is in use, it will instead apply an empty partition spec `()`, which means the table will not be partitioned.
 
 If you want to use partitioning, you must specify a custom partition specification using your own partition columns (columns that are not nested).
 
+NOTE: An empty partition spec `()` can cause a known issue in Amazon Redshift that prevents queries from running successfully on the table.
+
 === Manual deletion of Iceberg tables
 
 The AWS Glue catalog integration does not support automatic deletion of Iceberg tables from Redpanda. To manually delete Iceberg tables in AWS Glue, you must first set the cluster property config_ref:iceberg_delete,true,properties/cluster-properties[`iceberg_delete`] to `false` when you configure the catalog integration.