diff options
Diffstat (limited to 'src/backend/optimizer/plan/setrefs.c')
| -rw-r--r-- | src/backend/optimizer/plan/setrefs.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c index 707c1016c25..1cb0abdbc1f 100644 --- a/src/backend/optimizer/plan/setrefs.c +++ b/src/backend/optimizer/plan/setrefs.c @@ -1636,9 +1636,10 @@ set_append_references(PlannerInfo *root, /* * See if it's safe to get rid of the Append entirely. For this to be * safe, there must be only one child plan and that child plan's parallel - * awareness must match that of the Append's. The reason for the latter - * is that if the Append is parallel aware and the child is not, then the - * calling plan may execute the non-parallel aware child multiple times. + * awareness must match the Append's. The reason for the latter is that + * if the Append is parallel aware and the child is not, then the calling + * plan may execute the non-parallel aware child multiple times. (If you + * change these rules, update create_append_path to match.) */ if (list_length(aplan->appendplans) == 1) { @@ -1710,10 +1711,11 @@ set_mergeappend_references(PlannerInfo *root, /* * See if it's safe to get rid of the MergeAppend entirely. For this to * be safe, there must be only one child plan and that child plan's - * parallel awareness must match that of the MergeAppend's. The reason - * for the latter is that if the MergeAppend is parallel aware and the - * child is not then the calling plan may execute the non-parallel aware - * child multiple times. + * parallel awareness must match the MergeAppend's. The reason for the + * latter is that if the MergeAppend is parallel aware and the child is + * not, then the calling plan may execute the non-parallel aware child + * multiple times. (If you change these rules, update + * create_merge_append_path to match.) */ if (list_length(mplan->mergeplans) == 1) { |