Fix possible division by zero in pg_xlogdump.

When displaying stats it was possible that a floating point division by
zero occured when no FPIs were issued for a type of record.

Author: Abhijit Menon-Sen
Discussion: 20150417091811.GA14008@toroid.org

diff --git a/src/bin/pg_xlogdump/pg_xlogdump.c b/src/bin/pg_xlogdump/pg_xlogdump.c
index d634807eb5bf5e3a7fa78eb1e5f85ce4781d1dcc..e9cbbd264de484dde88bff18f1c5b47bef6d49de 100644 (file)
--- a/src/bin/pg_xlogdump/pg_xlogdump.c
+++ b/src/bin/pg_xlogdump/pg_xlogdump.c
@@ -489,18 +489,36 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
  */
 static void
 XLogDumpStatsRow(const char *name,
-                uint64 n, double n_pct,
-                uint64 rec_len, double rec_len_pct,
-                uint64 fpi_len, double fpi_len_pct,
-                uint64 total_len, double total_len_pct)
+                uint64 n, uint64 total_count,
+                uint64 rec_len, uint64 total_rec_len,
+                uint64 fpi_len, uint64 total_fpi_len,
+                uint64 tot_len, uint64 total_len)
 {
+   double      n_pct, rec_len_pct, fpi_len_pct, tot_len_pct;
+
+   n_pct = 0;
+   if (total_count != 0)
+       n_pct = 100 * (double) n / total_count;
+
+   rec_len_pct = 0;
+   if (total_rec_len != 0)
+       rec_len_pct = 100 * (double) rec_len / total_rec_len;
+
+   fpi_len_pct = 0;
+   if (total_fpi_len != 0)
+       fpi_len_pct = 100 * (double) fpi_len / total_fpi_len;
+
+   tot_len_pct = 0;
+   if (total_len != 0)
+       tot_len_pct = 100 * (double) tot_len / total_len;
+
    printf("%-27s "
           "%20" INT64_MODIFIER "u (%6.02f) "
           "%20" INT64_MODIFIER "u (%6.02f) "
           "%20" INT64_MODIFIER "u (%6.02f) "
           "%20" INT64_MODIFIER "u (%6.02f)\n",
           name, n, n_pct, rec_len, rec_len_pct, fpi_len, fpi_len_pct,
-          total_len, total_len_pct);
+          tot_len, tot_len_pct);
 }
 
 
@@ -515,6 +533,7 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
    uint64      total_rec_len = 0;
    uint64      total_fpi_len = 0;
    uint64      total_len = 0;
+   double      rec_len_pct, fpi_len_pct;
 
    /* ---
     * Make a first pass to calculate column totals:
@@ -557,10 +576,8 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
            tot_len = rec_len + fpi_len;
 
            XLogDumpStatsRow(desc->rm_name,
-                            count, 100 * (double) count / total_count,
-                            rec_len, 100 * (double) rec_len / total_rec_len,
-                            fpi_len, 100 * (double) fpi_len / total_fpi_len,
-                            tot_len, 100 * (double) tot_len / total_len);
+                            count, total_count, rec_len, total_rec_len,
+                            fpi_len, total_fpi_len, tot_len, total_len);
        }
        else
        {
@@ -583,10 +600,8 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
                    id = psprintf("UNKNOWN (%x)", rj << 4);
 
                XLogDumpStatsRow(psprintf("%s/%s", desc->rm_name, id),
-                                count, 100 * (double) count / total_count,
-                                rec_len, 100 * (double) rec_len / total_rec_len,
-                                fpi_len, 100 * (double) fpi_len / total_fpi_len,
-                                tot_len, 100 * (double) tot_len / total_len);
+                                count, total_count, rec_len, total_rec_len,
+                                fpi_len, total_fpi_len, tot_len, total_len);
            }
        }
    }
@@ -601,14 +616,22 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
     * them from the earlier ones, and are thus up to 9 characters long.
     */
 
+   rec_len_pct = 0;
+   if (total_len != 0)
+       rec_len_pct = 100 * (double) total_rec_len / total_len;
+
+   fpi_len_pct = 0;
+   if (total_len != 0)
+       fpi_len_pct = 100 * (double) total_fpi_len / total_len;
+
    printf("%-27s "
           "%20" INT64_MODIFIER "u %-9s"
           "%20" INT64_MODIFIER "u %-9s"
           "%20" INT64_MODIFIER "u %-9s"
           "%20" INT64_MODIFIER "u %-6s\n",
           "Total", stats->count, "",
-          total_rec_len, psprintf("[%.02f%%]", 100 * (double)total_rec_len / total_len),
-          total_fpi_len, psprintf("[%.02f%%]", 100 * (double)total_fpi_len / total_len),
+          total_rec_len, psprintf("[%.02f%%]", rec_len_pct),
+          total_fpi_len, psprintf("[%.02f%%]", fpi_len_pct),
           total_len, "[100%]");
 }