From 9b4c80fd0fd4d991f91544e075d32e72cb44fee3 Mon Sep 17 00:00:00 2001
From: Brian Fraser <brian.fraser@percona.com>
Date: Fri, 9 Nov 2012 10:32:22 -0300
Subject: [PATCH] Fixes for bugs 1074179 and the ptc part of 1050737: division
 by zero errors when nibble_time is zero

---
 bin/pt-table-checksum      | 11 ++++++-----
 t/pt-table-checksum/bugs.t | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/bin/pt-table-checksum b/bin/pt-table-checksum
index 5f92d279..7d5047a7 100755
--- a/bin/pt-table-checksum
+++ b/bin/pt-table-checksum
@@ -9232,14 +9232,15 @@ sub main {
             # Update the rate of rows per second for the entire server.
             # This is used for the initial chunk size of the next table.
             $total_rows += $cnt;
-            $total_time += $tbl->{nibble_time};
-            $total_rate  = int($total_rows / $total_time);
+            $total_time += ($tbl->{nibble_time} || 0);
+            $total_rate  = $total_time ? int($total_rows / $total_time) : 0;
             PTDEBUG && _d('Total avg rate:', $total_rate);
 
             # Adjust chunk size.  This affects the next chunk.
             if ( $o->get('chunk-time') ) {
-               $tbl->{chunk_size}
-                  = $tbl->{rate}->update($cnt, $tbl->{nibble_time});
+               $tbl->{chunk_size} = $tbl->{nibble_time}
+                                  ? $tbl->{rate}->update($cnt, $tbl->{nibble_time})
+                                  : $o->get('chunk-time');
 
                if ( $tbl->{chunk_size} < 1 ) {
                   # This shouldn't happen.  WeightedAvgRate::update() may return
@@ -9255,7 +9256,7 @@ sub main {
                         . "or increase --chunk-time.  The last chunk, number "
                         . "$chunk of table $tbl->{db}.$tbl->{tbl}, "
                         . "selected $cnt rows and took "
-                        . sprintf('%.3f', $tbl->{nibble_time})
+                        . sprintf('%.3f', $tbl->{nibble_time} || 0)
                         . " seconds to execute.\n");
                   }
                }
diff --git a/t/pt-table-checksum/bugs.t b/t/pt-table-checksum/bugs.t
index f31e6a86..5cb46a15 100644
--- a/t/pt-table-checksum/bugs.t
+++ b/t/pt-table-checksum/bugs.t
@@ -192,6 +192,40 @@ like(
    "Bug 1016131: ptc should skip tables where all columns are excluded"
 );
 
+# #############################################################################
+# Illegal division by zero at pt-table-checksum line 7950
+# https://bugs.launchpad.net/percona-toolkit/+bug/1075638
+# and the ptc part of
+# divison by zero errors on default Gentoo mysql
+# https://bugs.launchpad.net/percona-toolkit/+bug/1050737
+# #############################################################################
+
+{
+   no warnings qw(redefine once);
+   my $orig = \&Time::HiRes::time;
+   my $time = Time::HiRes::time();
+   local *pt_table_checksum::time = local *Time::HiRes::time = sub { $time };
+
+   ($output) = output(
+      sub { pt_table_checksum::main(@args,
+               qw(--replicate=pt.checksums -t test.t --chunk-size 10))
+      },
+      stderr => 1
+   );
+
+   unlike(
+      $output,
+      qr/Illegal division by zero/,
+      "Bugs 1075638 and 1050737: No division by zero error when nibble_time is zero"
+   );
+
+   is(
+      PerconaTest::count_checksum_results($output, 'diffs'),
+      3,
+      "Bug 1075638 and 1050737: ...And we get the correct number of diffs"
+   );
+}
+
 # #############################################################################
 # pt-table-checksum doesn't warn if binlog_format=row or mixed on slaves
 # https://bugs.launchpad.net/percona-toolkit/+bug/938068