Cosmetic fixes for radix sort

Do minor comment fixes and remove implicit cast to Datum.

While here, let's prefer crashing instead of entering an infinite
loop in case of future programming mistakes when computing next_level,
suggested by ChangAo Chen.

Discussion: https://postgr.es/m/tencent_49E3F11E74D8A584A2144ED532A490CBC40A@qq.com

diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 72c2c2995d8da98253f98e96508b2186ab924de2..c0e7527b9ca369ad9ac3b79bb3854f8975bff4c5 100644 (file)
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -2589,7 +2589,7 @@ normalize_datum(Datum orig, SortSupport ssup)
 
        if (ssup->comparator == ssup_datum_signed_cmp)
        {
-               norm_datum1 = orig + ((uint64) PG_INT64_MAX) + 1;
+               norm_datum1 = orig + (Int64GetDatum(PG_INT64_MAX)) + 1;
        }
        else if (ssup->comparator == ssup_datum_int32_cmp)
        {
@@ -2620,8 +2620,8 @@ normalize_datum(Datum orig, SortSupport ssup)
  * Radix sort by (pass-by-value) datum1, diverting to qsort_tuple()
  * for tiebreaks.
  *
- * This is a modification of
- * ska_byte_sort() from https://github.com/skarupke/ska_sort
+ * This is a modification of ska_byte_sort() from
+ * https://github.com/skarupke/ska_sort
  * The original copyright notice follows:
  *
  * Copyright Malte Skarupke 2016.
@@ -2783,6 +2783,8 @@ radix_sort_recursive(SortTuple *begin, size_t n_elems, int level, Tuplesortstate
        else
                next_level = level + 1;
 
+       Assert(next_level > level);
+
        for (uint8 *rp = remaining_partitions;
                 rp < remaining_partitions + num_partitions;
                 rp++)
@@ -2849,7 +2851,8 @@ radix_sort_tuple(SortTuple *data, size_t n, Tuplesortstate *state)
        /*
         * Find the first NOT NULL if NULLS FIRST, or first NULL if NULLS LAST.
         * This also serves as a quick check for the common case where all tuples
-        * are NOT NULL in the first sort key.
+        * are NOT NULL in the first sort key with the default order ASC NULLS
+        * LAST.
         */
        while (d1 < n && data[d1].isnull1 == nulls_first)
        {