injection_points: Improve comment about disabled isolation permutation

michaelpq · michaelpq · commit baa1ae04299f · 2024-10-31T08:28:20.000+09:00
9f00edc has disabled a permutation due to failures in the CI for FreeBSD environments, but this is a matter of timing. Let's document properly why this type of permutation is a bad idea if relying on a wait done in a SQL function, so as this can be avoided when implementing new tests (this spec is also a template). Reviewed-by: Bertrand Drouvot Discussion: https://postgr.es/m/ZyCa2qsopKaw3W3K@paquier.xyz
diff --git a/src/test/modules/injection_points/specs/basic.spec b/src/test/modules/injection_points/specs/basic.spec
@@ -26,7 +26,10 @@ step wakeup2	{ SELECT injection_points_wakeup('injection-points-wait'); }
 step detach2	{ SELECT injection_points_detach('injection-points-wait'); }
 
 # Detach after wait and wakeup.
-# This permutation is proving to be unstable on FreeBSD, so disable for now.
+# Permutations like the following one commented out should be avoided, as
+# the detach may finish before the SQL function doing the wait returns
+# its result.  It is recommended to use wakeups as the last permutation
+# should a wait be done within an SQL function.
 #permutation wait1 wakeup2 detach2
 
 # Detach before wakeup.  s1 waits until wakeup, ignores the detach.
