Re: MERGE ... RETURNING

On Thu, Jul 6, 2023 at 4:07 AM jian he <jian(dot)universality(at)gmail(dot)com> wrote:
>
> On Thu, Jul 6, 2023 at 1:13 PM Gurjeet Singh <gurjeet(at)singh(dot)im> wrote:

> > I think the name of function pg_merge_when_clause() can be improved.
> > How about pg_merge_when_clause_ordinal().
>
> another idea: pg_merge_action_ordinal()

Since there can be many occurrences of the same action
(INSERT/UPDATE/DELETE) in a MERGE command associated with different
conditions, I don't think action_ordinal would make sense for this
function name.

e.g.
WHEN MATCHED and src.col1 = val1 THEN UPDATE col2 = someval1
WHEN MATCHED and src.col1 = val2 THEN UPDATE col2 = someval2
...

When looking at the implementation code, as well, we see that the code
in this function tracks and reports the lexical position of the WHEN
clause, irrespective of the action associated with that WHEN clause.

foreach(l, stmt->mergeWhenClauses)
{
...
action->index = foreach_current_index(l) + 1;

Best regards,
Gurjeet
http://Gurje.et