From 582f8b932cc515485bfdb84479f0600f91bbf9a7 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 18 May 2022 18:41:04 +0200
Subject: [PATCH v4] Link to MVCC docs in MERGE docs

---
 doc/src/sgml/mvcc.sgml      | 15 ++++++++-------
 doc/src/sgml/ref/merge.sgml |  4 ++++
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
index 341fea524a..2f8d2b17ef 100644
--- a/doc/src/sgml/mvcc.sgml
+++ b/doc/src/sgml/mvcc.sgml
@@ -425,13 +425,13 @@ COMMIT;
    <para>
     <command>MERGE</command> allows the user to specify various
     combinations of <command>INSERT</command>, <command>UPDATE</command>
-    or <command>DELETE</command> subcommands. A <command>MERGE</command>
+    and <command>DELETE</command> subcommands. A <command>MERGE</command>
     command with both <command>INSERT</command> and <command>UPDATE</command>
     subcommands looks similar to <command>INSERT</command> with an
     <literal>ON CONFLICT DO UPDATE</literal> clause but does not
     guarantee that either <command>INSERT</command> or
     <command>UPDATE</command> will occur.
-    If MERGE attempts an <command>UPDATE</command> or
+    If <command>MERGE</command> attempts an <command>UPDATE</command> or
     <command>DELETE</command> and the row is concurrently updated but
     the join condition still passes for the current target and the
     current source tuple, then <command>MERGE</command> will behave
@@ -448,9 +448,9 @@ COMMIT;
     and execute the first one that succeeds.
     If <command>MERGE</command> attempts an <command>INSERT</command>
     and a unique index is present and a duplicate row is concurrently
-    inserted, then a uniqueness violation is raised.
-    <command>MERGE</command> does not attempt to avoid the
-    error by executing an <command>UPDATE</command>.
+    inserted, then a uniqueness violation error is raised;
+    <command>MERGE</command> does not attempt to avoid such
+    errors by evaluating <literal>MATCHED</literal> conditions.
    </para>
 
    <para>
@@ -516,8 +516,9 @@ COMMIT;
    </para>
 
    <para>
-    <command>UPDATE</command>, <command>DELETE</command>, <command>SELECT
-    FOR UPDATE</command>, and <command>SELECT FOR SHARE</command> commands
+    <command>UPDATE</command>, <command>DELETE</command>,
+    <command>MERGE</command>, <command>SELECT FOR UPDATE</command>,
+    and <command>SELECT FOR SHARE</command> commands
     behave the same as <command>SELECT</command>
     in terms of searching for target rows: they will only find target rows
     that were committed as of the transaction start time.  However, such a
diff --git a/doc/src/sgml/ref/merge.sgml b/doc/src/sgml/ref/merge.sgml
index f68aa09736..f0745d01c7 100644
--- a/doc/src/sgml/ref/merge.sgml
+++ b/doc/src/sgml/ref/merge.sgml
@@ -539,6 +539,10 @@ MERGE <replaceable class="parameter">total_count</replaceable>
   </para>
 
   <para>
+   When <command>MERGE</command> is run concurrently with other commands
+   that modify the target table, the usual transaction isolation rules
+   apply; see <xref linkend="transaction-iso"/> for an explanation
+   on the behavior at each isolation level.
    You may also wish to consider using <command>INSERT ... ON CONFLICT</command>
    as an alternative statement which offers the ability to run an
    <command>UPDATE</command> if a concurrent <command>INSERT</command>
-- 
2.30.2