Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, Aug 16, 2017 at 11:56 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I can get on board with that statement. Can you draft a better wording?
> Here is an attempt. Feel free to edit.
I think s/plan/query/ in the last bit would be better. Perhaps
+ * However, if force_parallel_mode = on or force_parallel_mode = regress,
+ * then we impose parallel mode whenever it's safe to do so, even if the
+ * final plan doesn't use parallelism. It's not safe to do so if the query
+ * contains anything parallel-unsafe; parallelModeOK will be false in that
+ * case. Otherwise, everything in the query is either parallel-safe or
+ * parallel-restricted, and in either case it should be OK to impose
+ * parallel-mode restrictions. If that ends up breaking something, then
+ * either some function the user included in the query is incorrectly
+ * labelled as parallel-safe or parallel-restricted when in reality it's
+ * parallel-unsafe, or else the query planner itself has a bug. */
regards, tom lane