1 files changed, 16 insertions, 0 deletions
diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index a3639e96042..ad37a742213 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -391,6 +391,22 @@ foreign_expr_walker(Node *node,
 				Param	   *p = (Param *) node;
 
 				/*
+				 * If it's a MULTIEXPR Param, punt.  We can't tell from here
+				 * whether the referenced sublink/subplan contains any remote
+				 * Vars; if it does, handling that is too complicated to
+				 * consider supporting at present.  Fortunately, MULTIEXPR
+				 * Params are not reduced to plain PARAM_EXEC until the end of
+				 * planning, so we can easily detect this case.  (Normal
+				 * PARAM_EXEC Params are safe to ship because their values
+				 * come from somewhere else in the plan tree; but a MULTIEXPR
+				 * references a sub-select elsewhere in the same targetlist,
+				 * so we'd be on the hook to evaluate it somehow if we wanted
+				 * to handle such cases as direct foreign updates.)
+				 */
+				if (p->paramkind == PARAM_MULTIEXPR)
+					return false;
+
+				/*
 				 * Collation rule is same as for Consts and non-foreign Vars.
 				 */
 				collation = p->paramcollid;