diff options
Diffstat (limited to 'src/backend/executor/nodeSubplan.c')
| -rw-r--r-- | src/backend/executor/nodeSubplan.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/backend/executor/nodeSubplan.c b/src/backend/executor/nodeSubplan.c index 62ef1385710..ede4e4bbfae 100644 --- a/src/backend/executor/nodeSubplan.c +++ b/src/backend/executor/nodeSubplan.c @@ -246,6 +246,21 @@ ExecScanSubPlan(SubPlanState *node, * ones, so this should be safe.) Unlike ExecReScanSetParamPlan, we do * *not* set bits in the parent plan node's chgParam, because we don't * want to cause a rescan of the parent. + * + * Note: we are also relying on MULTIEXPR SubPlans not sharing any output + * parameters with other SubPlans, because if one does then it is unclear + * which SubPlanState node the parameter's execPlan field will be pointing + * to when we come to evaluate the parameter. We can allow plain initplan + * SubPlans to share output parameters, because it doesn't actually matter + * which initplan SubPlan we reference as long as they all point to the + * same underlying subplan. However, that fails to hold for MULTIEXPRs + * because they can have non-empty args lists, and the "same" args might + * have mutated into different forms in different parts of a plan tree. + * There is not a problem in ordinary queries because MULTIEXPR will + * appear only in an UPDATE's top-level target list, so it won't get + * duplicated anyplace. However, when inheritance_planner clones a + * partially-planned targetlist it must take care to assign non-duplicate + * param IDs to the cloned copy. */ if (subLinkType == MULTIEXPR_SUBLINK) { |