As of commit
e5253fdc, it is no longer true that the leader always
executes the subplan of a Gather Merge node. Remove comment to that
effect.
Back-patch to 11.
Discussion: https://postgr.es/m/CA%2BhUKGJEaZJYezXAOutuiWT%2BfxCA44%2BoKtVPAND2ubLiigR%3D-w%40mail.gmail.com
/*
* GatherMergePath runs several copies of a plan in parallel and collects
- * the results, preserving their common sort order. For gather merge, the
- * parallel leader always executes the plan too, so we don't need single_copy.
+ * the results, preserving their common sort order.
*/
typedef struct GatherMergePath
{