Rewrite pg_size_pretty() to avoid compiler bug.

Convert it to use successive shifts right instead of increasing a divisor.
This is probably a tad more efficient than the original coding, and it's
nicer-looking than the previous patch because we don't need a special case
to avoid overflow in the last branch.  But the real reason to do it is to
avoid a Solaris compiler bug, as per results from buildfarm member moa.

diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
index 83026b6dde4fbeb90dd6ee07384d0ae417a259e6..0bbc02e5ad729de51989880190d48305c3aefb5a 100644 (file)
--- a/src/backend/utils/adt/dbsize.c
+++ b/src/backend/utils/adt/dbsize.c
@@ -473,39 +473,33 @@ pg_size_pretty(PG_FUNCTION_ARGS)
        int64           size = PG_GETARG_INT64(0);
        char            buf[64];
        int64           limit = 10 * 1024;
-       int64           mult = 1;
+       int64           limit2 = limit * 2 - 1;
 
-       if (size < limit * mult)
+       if (size < limit)
                snprintf(buf, sizeof(buf), INT64_FORMAT " bytes", size);
        else
        {
-               mult *= 1024;
-               if (size < limit * mult)
+               size >>= 9;                             /* keep one extra bit for rounding */
+               if (size < limit2)
                        snprintf(buf, sizeof(buf), INT64_FORMAT " kB",
-                                        (size + mult / 2) / mult);
+                                        (size + 1) / 2);
                else
                {
-                       mult *= 1024;
-                       if (size < limit * mult)
+                       size >>= 10;
+                       if (size < limit2)
                                snprintf(buf, sizeof(buf), INT64_FORMAT " MB",
-                                                (size + mult / 2) / mult);
+                                                (size + 1) / 2);
                        else
                        {
-                               mult *= 1024;
-                               if (size < limit * mult)
+                               size >>= 10;
+                               if (size < limit2)
                                        snprintf(buf, sizeof(buf), INT64_FORMAT " GB",
-                                                        (size + mult / 2) / mult);
+                                                        (size + 1) / 2);
                                else
                                {
-                                       /* Here we have to worry about avoiding overflow */
-                                       int64   val;
-
-                                       mult *= 1024;
-                                       val = size / mult;
-                                       if ((size % mult) >= (mult / 2))
-                                               val++;
+                                       size >>= 10;
                                        snprintf(buf, sizeof(buf), INT64_FORMAT " TB",
-                                                        val);
+                                                        (size + 1) / 2);
                                }
                        }
                }