Add a comment to AdjustIntervalForTypmod to reduce chance of future bugs.

It's not entirely evident how the logic here relates to the
interval_transform function, so let's clue people in that they need to
check that if the rules change.

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 12af7f69f69051bf467e6b51f84e85ae7e323690..db434dcb3cc685758e009adcea9ba60c7f4abe77 100644 (file)
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -1069,7 +1069,8 @@ AdjustIntervalForTypmod(Interval *interval, int32 typmod)
                 * nonzero "month" field.  However that seems a bit pointless when we
                 * can't do it consistently.  (We cannot enforce a range limit on the
                 * highest expected field, since we do not have any equivalent of
-                * SQL's <interval leading field precision>.)
+                * SQL's <interval leading field precision>.)  If we ever decide to
+                * revisit this, interval_transform will likely requite adjusting.
                 *
                 * Note: before PG 8.4 we interpreted a limited set of fields as
                 * actually causing a "modulo" operation on a given value, potentially