Date: Wed, 11 May 2022 11:33:50 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	Amit Langote <amitlangote09@gmail.com>,
	Japin Li <japinli@hotmail.com>, Zhihong Yu <zyu@yugabyte.com>,
	Simon Riggs <simon.riggs@enterprisedb.com>,
	pgsql-hackers@lists.postgresql.org,
	Tomas Vondra <tomas.vondra@enterprisedb.com>,
	Daniel Westermann <dwe@dbi-services.com>,
	Erik Rijkers <er@xs4all.nl>,
	Jaime Casanova <jcasanov@systemguards.com.ec>,
	Andres Freund <andres@anarazel.de>
Subject: Re: support for MERGE
Message-ID: <20220511163350.GL19626@telsasoft.com>
References: <202203281100.qa7wqdu2ooyy@alvherre.pgsql>
 <202203281506.se4wtcvtvdq3@alvherre.pgsql>
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I suggest to reference the mvcc docs from the merge docs, or to make the merge
docs themselves include the referenced information.

diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
index 341fea524a1..4446e1c484e 100644
--- a/doc/src/sgml/mvcc.sgml
+++ b/doc/src/sgml/mvcc.sgml
@@ -425,7 +425,7 @@ 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
diff --git a/doc/src/sgml/ref/merge.sgml b/doc/src/sgml/ref/merge.sgml
index f68aa09736c..99dd5814f36 100644
--- a/doc/src/sgml/ref/merge.sgml
+++ b/doc/src/sgml/ref/merge.sgml
@@ -544,6 +544,7 @@ MERGE <replaceable class="parameter">total_count</replaceable>
    <command>UPDATE</command> if a concurrent <command>INSERT</command>
    occurs.  There are a variety of differences and restrictions between
    the two statement types and they are not interchangeable.
+   See <xref linkend="mvcc"/> for more information.
   </para>
  </refsect1>
 

Also, EXPLAIN output currently looks like this:

| Merge on ex_mtarget t (actual rows=0 loops=1)
|   Tuples Inserted: 0
|   Tuples Updated: 50
|   Tuples Deleted: 0
|   Tuples Skipped: 0

Should the "zero" rows be elided from the text output ?
And/or, should it use a more compact output format ?

There are two output formats already in use, so the options would look like
this:

   Tuples: Inserted: 1  Updated: 2  Deleted: 3  Skipped: 4
or
   Tuples: inserted=1 updated=2 deleted=3 skipped=4

Note double spaces and capitals.
That's separate from the question about eliding zeros.