Rename force_parallel_mode to debug_parallel_query

force_parallel_mode is meant to be used to allow us to exercise the
parallel query infrastructure to ensure that it's working as we expect.
It seems some users think this GUC is for forcing the query planner into
picking a parallel plan regardless of the costs.  A quick look at the
documentation would have made them realize that they were wrong, but the
GUC is likely too conveniently named which, evidently, seems to often
result in users expecting that it forces the planner into usefully
parallelizing queries.

Here we rename the GUC to something which casual users are less likely to
mistakenly think is what they need to make their query run more quickly.

For now, the old name can still be used.  We'll revisit if the old name
mapping can be removed once the buildfarm configs are all updated.

Reviewed-by: John Naylor
Discussion: https://postgr.es/m/CAApHDvrsOi92_uA7PEaHZMH-S4Xv+MGhQWA+GrP8b1kjpS1HjQ@mail.gmail.com

1 files changed, 2 insertions, 2 deletions

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index 9e3ec0d5d8a..b26f2a64fbc 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -1152,11 +1152,11 @@ HandleParallelMessage(ParallelContext *pcxt, int i, StringInfo msg)
 				 * If desired, add a context line to show that this is a
 				 * message propagated from a parallel worker.  Otherwise, it
 				 * can sometimes be confusing to understand what actually
-				 * happened.  (We don't do this in FORCE_PARALLEL_REGRESS mode
+				 * happened.  (We don't do this in DEBUG_PARALLEL_REGRESS mode
 				 * because it causes test-result instability depending on
 				 * whether a parallel worker is actually used or not.)
 				 */
-				if (force_parallel_mode != FORCE_PARALLEL_REGRESS)
+				if (debug_parallel_query != DEBUG_PARALLEL_REGRESS)
 				{
 					if (edata.context)
 						edata.context = psprintf("%s\n%s", edata.context,