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%]");
 }