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/
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