Improve interval_transform function to detect a few more cases.

Noah Misch, per a review comment from me.

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 44a3a922ece61f3bbb86236c0497a1bc87e3c21b..12af7f69f69051bf467e6b51f84e85ae7e323690 100644 (file)
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -958,6 +958,7 @@ interval_transform(PG_FUNCTION_ARGS)
                int                     new_range = INTERVAL_RANGE(new_typmod);
                int                     new_precis = INTERVAL_PRECISION(new_typmod);
                int                     new_range_fls;
+               int                     old_range_fls;
 
                if (old_typmod == -1)
                {
@@ -974,12 +975,16 @@ interval_transform(PG_FUNCTION_ARGS)
                 * Temporally-smaller fields occupy higher positions in the range
                 * bitmap.  Since only the temporally-smallest bit matters for length
                 * coercion purposes, we compare the last-set bits in the ranges.
+                * Precision, which is to say, sub-second precision, only affects
+                * ranges that include SECOND.
                 */
                new_range_fls = fls(new_range);
+               old_range_fls = fls(old_range);
                if (new_typmod == -1 ||
                        ((new_range_fls >= SECOND ||
-                         new_range_fls >= fls(old_range)) &&
-                        (new_precis >= MAX_INTERVAL_PRECISION ||
+                         new_range_fls >= old_range_fls) &&
+                        (old_range_fls < SECOND ||
+                         new_precis >= MAX_INTERVAL_PRECISION ||
                          new_precis >= old_precis)))
                        ret = relabel_to_typmod(source, new_typmod);
        }