Re: updatable cursors and ORDER BY

On 5/9/18 22:57, Tom Lane wrote:
> I think you misread that note: it says nothing about what is allowed
> in DECLARE CURSOR per se.  It is talking about whether you can apply
> UPDATE/DELETE WHERE CURRENT OF to that cursor.  Moreover, what it says
> is that if you use FOR UPDATE then such an UPDATE/DELETE *will* work,
> whereas without it we don't guarantee that.

I think that last part isn't actually written down anywhere.  (It only
states the converse.)  How about a clarification like this:

@@ -271,7 +271,10 @@ <title id="sql-declare-notes-title">Notes</title>
      and not use grouping or <literal>ORDER BY</literal>).  Cursors
      that are not simply updatable might work, or might not, depending on plan
      choice details; so in the worst case, an application might work in testing
-     and then fail in production.
+     and then fail in production.  If <literal>FOR UPDATE</literal> is
+     specified, then the cursor is guaranteed to be updatable, or the
+     <command>DECLARE</command> command will error if an updatable cursor
+     cannot be created for the supplied query.
     </para>

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services