diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 110f6b4657..15e62b2d8a 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -3465,6 +3465,18 @@ VALUES ('Albany', NULL, NULL, 'NY');
      offer flexibility but do not have some of the performance benefits
      of built-in declarative partitioning.
     </para>
+
+    <note>
+     <para>
+      When using either declarative partitioning or table inheritance,
+      partitioning hierarchies with more than a few hundred partitions are
+      not currently recommended.  Larger partition hierarchies may incur long
+      planning time, and especially in the case of <command>UPDATE</command>
+      and <command>DELETE</command>, excessive memory usage.  When inheritance
+      is used, see also the limitations described in
+      <xref linkend="ddl-partitioning-constraint-exclusion"/>.
+     </para>
+    </note>
    </sect2>
 
   <sect2 id="ddl-partitioning-declarative">