From a77650dda3c724b7ad89926874b8e5f29c80f327 Mon Sep 17 00:00:00 2001
From: wangw <wangw.fnst@fujitsu.com>
Date: Fri, 17 Dec 2021 04:30:32 +0800
Subject: [PATCH] Correct wrong comment about REPLICA_IDENTITY_INDEX.

The comment about REPLICA_IDENTITY_INDEX is wrong.
When drop relation's replica identity index like the comment, the action is not
as same as DEFAULT. Just like NOTHING.

So correct this comment. And add this use case to PG-doc.
By the way, improve PG-doc to make it easier for users to read.
---
 doc/src/sgml/ref/alter_table.sgml | 50 ++++++++++++++++++++++++++-----
 src/include/catalog/pg_class.h    |  2 +-
 2 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 8f14e4a5c4..1081d8d7bd 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -872,16 +872,50 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
      <para>
       This form changes the information which is written to the write-ahead log
       to identify rows which are updated or deleted.  This option has no effect
-      except when logical replication is in use.  <literal>DEFAULT</literal>
-      (the default for non-system tables) records the
-      old values of the columns of the primary key, if any.  <literal>USING INDEX</literal>
-      records the old values of the columns covered by the named index, which
-      must be unique, not partial, not deferrable, and include only columns marked
-      <literal>NOT NULL</literal>.  <literal>FULL</literal> records the old values of all columns
-      in the row.  <literal>NOTHING</literal> records no information about the old row.
-      (This is the default for system tables.)
+      except when logical replication is in use.
       In all cases, no old values are logged unless at least one of the columns
       that would be logged differs between the old and new versions of the row.
+     <variablelist>
+      <varlistentry>
+       <term><literal>DEFAULT</literal></term>
+       <listitem>
+        <para>
+         The default for non-system tables. Records the old values of the columns
+         of the primary key, if any. The default for non-system tables. 
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><literal>USING INDEX index_name</literal></term>
+       <listitem>
+        <para>
+         Records the old values of the columns covered by the named index, which
+         must be unique, not partial,not deferrable, and include only columns
+         marked <literal>NOT NULL</literal>. If replica identity index is dropped,
+         the behavior is the same as <literal>NOTHING</literal>.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><literal>FULL</literal></term>
+       <listitem>
+        <para>
+         Records the old values of all columns in the row.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><literal>NOTHING</literal></term>
+       <listitem>
+        <para>
+         Records no information about the old row.(This is the default for system tables.)
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
      </para>
     </listitem>
    </varlistentry>
diff --git a/src/include/catalog/pg_class.h b/src/include/catalog/pg_class.h
index 93338d267c..b46299048e 100644
--- a/src/include/catalog/pg_class.h
+++ b/src/include/catalog/pg_class.h
@@ -182,7 +182,7 @@ DECLARE_INDEX(pg_class_tblspc_relfilenode_index, 3455, ClassTblspcRelfilenodeInd
 /*
  * an explicitly chosen candidate key's columns are used as replica identity.
  * Note this will still be set if the index has been dropped; in that case it
- * has the same meaning as 'd'.
+ * has the same meaning as 'n'.
  */
 #define		  REPLICA_IDENTITY_INDEX	'i'
 
-- 
2.27.0