Re: support for MERGE

On Fri, 21 Jan 2022 at 05:06, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> Here's v8 of this patch.  I have fixed the problems pointed out by Jaime
> and Erik, as well as incorporated Zhihong, Erik and Justin's
> documentation fixes (typos and otherwise).
>
> Not yet included: a fix for Peter's suggestion to raise a good error
> when both tables use the same name.
>
> Individual changes can also be seen in 
> https://github.com/alvherre/postgres/commits/merge-15

+               /*
+                * NOT MATCHED actions can't see target relation, but they can see
+                * source relation.
+                */
+               Assert(mergeWhenClause->commandType == CMD_INSERT ||
+                          mergeWhenClause->commandType == CMD_DELETE ||
+                          mergeWhenClause->commandType == CMD_NOTHING);
+               setNamespaceVisibilityForRTE(pstate->p_namespace,
+                                                                        targetRelRTE, false, false);
+               setNamespaceVisibilityForRTE(pstate->p_namespace,
+                                                                        sourceRelRTE, true, true);

Should we remove the CMD_DELETE from Assert(), since it will not happened
according to MERGE syntax?

-- 
Regrads,
Japin Li.
ChengDu WenWu Information Technology Co.,Ltd.