Re: MERGE ... WHEN NOT MATCHED BY SOURCE

On 2023-Mar-19, Dean Rasheed wrote:

> diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
> new file mode 100644
> index efe88cc..e1ebc8d
> --- a/src/backend/parser/gram.y
> +++ b/src/backend/parser/gram.y

> +merge_when_tgt_matched:
> + WHEN MATCHED { $$ = MERGE_WHEN_MATCHED; }
> + | WHEN NOT MATCHED BY SOURCE { $$ = MERGE_WHEN_NOT_MATCHED_BY_SOURCE; }
> + ;

I think a one-line comment on why this "matched" production matches "NOT
MATCHED BY" would be useful. I think you have a big one in
transformMergeStmt already.

> + /* Combine it with the action's WHEN condition */
> + if (action->qual == NULL)
> + action->qual = (Node *) ntest;
> + else
> + action->qual =
> + (Node *) makeBoolExpr(AND_EXPR,
> + list_make2(ntest, action->qual),
> + -1);

Hmm, I think ->qual is already in implicit-and form, so do you really
need to makeBoolExpr, or would it be sufficient to append this new
condition to the list?

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"El miedo atento y previsor es la madre de la seguridad" (E. Burke)