From 3de122082dd701d8056d388190a425760b2bb3d6 Mon Sep 17 00:00:00 2001
From: jian he <jian.universality@gmail.com>
Date: Wed, 12 Aug 2026 13:00:09 +0800
Subject: [PATCH v50 1/1] Add a warning in select.sgml

warning that pg_dump | pg_restore may fail because DEFINE clause does not allow
expression have table qualification or column alias.
---
 doc/src/sgml/ref/select.sgml | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index d317b896e0..062dd6804e 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -1014,7 +1014,7 @@ WINDOW <replaceable class="parameter">window_name</replaceable> AS ( <replaceabl
     The <replaceable class="parameter">frame_clause</replaceable> can be one of
 
 <synopsis>
-{ RANGE | ROWS | GROUPS } <replaceable>frame_start</replaceable> [ <replaceable>frame_exclusion</replaceable> ] [ <replaceable>row_pattern_common_syntax</replaceable> ]
+{ RANGE | ROWS | GROUPS } <replaceable>frame_start</replaceable> [ <replaceable>frame_exclusion</replaceable> ]
 { RANGE | ROWS | GROUPS } BETWEEN <replaceable>frame_start</replaceable> AND <replaceable>frame_end</replaceable> [ <replaceable>frame_exclusion</replaceable> ] [ <replaceable>row_pattern_common_syntax</replaceable> ]
 </synopsis>
 
@@ -1207,7 +1207,6 @@ DEFINE <replaceable class="parameter">definition_variable_name</replaceable> AS
    <para>
     Note that the maximum number of unique pattern variables
     used in the <literal>PATTERN</literal> clause is 240.
-    If this limit is exceeded, an error will be raised.
     Additionally, the maximum nesting depth of pattern groups
     (parentheses) is 254 levels.
     However, pattern optimizations such as flattening nested sequences
@@ -1244,6 +1243,28 @@ DEFINE <replaceable class="parameter">definition_variable_name</replaceable> AS
     <xref linkend="syntax-window-functions"/>, and
     <xref linkend="queries-window"/>.
    </para>
+
+   <warning>
+    <para>
+     According to the SQL standard, a column reference in a
+     <literal>DEFINE</literal> clause cannot be qualified by a table name or
+     alias; only row pattern variables may be used as qualifiers there.
+     Column names referenced in <literal>DEFINE</literal> must therefore be
+     unique across the entire <literal>FROM</literal> clause; an ambiguous
+     name is rejected.  The workaround is to rename columns in the
+     <literal>FROM</literal> clause (for example, with a column alias in a
+     subquery).
+    </para>
+
+    <para>
+     This also affects <application>pg_dump</application> and <application>pg_restore</application>.
+     A view can be created while a <literal>DEFINE</literal> referenced column name
+     is still unique, but if a later schema change (such as adding or renaming a
+     column) introduces a duplicate of that name, the view's definition keeps working while
+     its dumped definition no longer valid, restoring it fails with a
+     <quote>column reference is ambiguous</quote> error.
+    </para>
+   </warning>
   </refsect2>
 
   <refsect2 id="sql-select-list" xreflabel="SELECT List">
-- 
2.39.5 (Apple Git-154)