Re: PlaceHolderVars in pushed down child-join cause error

On Thu, Feb 22, 2018 at 7:41 AM, Ashutosh Bapat
<ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
> postgres_fdw isn't expected to push down joins with placeholder vars.
> But the check for that in foreign_join_ok() only considers
> joinrel->relids. For a child-join relids contains the child relids but
> PlaceHolderInfo refers to the top parent's relids. Hence postgres_fdw
> tries to push down a child-join with PlaceHolderVars in it and fails
> with error "unsupported expression type for deparse: 198". 198 being
> T_PlaceHolderVar.
>
> The fix is to use joinrel->top_parent_relids for a child-join.
> Attached patch for the same.

Committed, but I changed the formatting, because as you had it,
pgindent would have mangled it. While I was at it, I tweaked the
wording of the comment a bit.

--
Robert Haas
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