Add comment about default partition in check_new_partition_bound

The intention of the test is not immediately obvious, so we need this
much.

diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index 0f5932feeef700515d9eb5dd41114ecabdce34d9..55130e66e4b23968eea0524d720c3e8ed204b112 100644 (file)
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -858,6 +858,12 @@ check_new_partition_bound(char *relname, Relation parent,
 
    if (spec->is_default)
    {
+       /*
+        * The default partition bound never conflicts with any other
+        * partition's; if that's what we're attaching, the only possible
+        * problem is that one already exists, so check for that and we're
+        * done.
+        */
        if (boundinfo == NULL || !partition_bound_has_default(boundinfo))
            return;