Re: BUG #17579: 15beta2: strange error when trying to use MERGE statement as a CTE

On 2022-Aug-11, Richard Guo wrote:

> Seems we neglect to think of MERGE statements when we transform WITH
> clauses and when we rewrite the query. If we add the check against MERGE
> statement in parse_cte.c and in rewriteHandler.c, the query in problem
> can work. But I'm not sure if that's enough.

I would like to have MERGE within CTEs, but I think for it to be truly
useful we need a RETURNING clause, which is currently not implemented.
I don't think it's terribly difficult to implement ... AFAICS most of
the pieces are there ... but clearly out of scope for pg15.

> +1 to disallow it for now.

This patch does that.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/