From 9a788e16df9ae45f975b6a4238918d4882d05847 Mon Sep 17 00:00:00 2001
From: Brian Fraser <brian.fraser@percona.com>
Date: Thu, 16 Aug 2012 14:07:58 -0300
Subject: [PATCH] Fix for 930693: ChangeHandler and text columns with just
 whitespace

---
 bin/pt-table-sync     | 2 +-
 bin/pt-upgrade        | 2 +-
 lib/ChangeHandler.pm  | 5 ++++-
 t/lib/ChangeHandler.t | 4 ++--
 4 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/bin/pt-table-sync b/bin/pt-table-sync
index 2207c55b..f1835661 100755
--- a/bin/pt-table-sync
+++ b/bin/pt-table-sync
@@ -3512,7 +3512,7 @@ sub make_fetch_back_query {
             my $col = $_;
             if (    $self->{hex_blob}
                  && $tbl_struct->{type_for}->{$col} =~ m/blob|text|binary/ ) {
-               $col = "IF(`$col`='', '', CONCAT('0x', HEX(`$col`))) AS `$col`";
+               $col = "IF(BINARY(`$col`)='', '', CONCAT('0x', HEX(`$col`))) AS `$col`";
             }
             else {
                $col = "`$col`";
diff --git a/bin/pt-upgrade b/bin/pt-upgrade
index daa72ddc..9c0aea3a 100755
--- a/bin/pt-upgrade
+++ b/bin/pt-upgrade
@@ -4746,7 +4746,7 @@ sub make_fetch_back_query {
             my $col = $_;
             if (    $self->{hex_blob}
                  && $tbl_struct->{type_for}->{$col} =~ m/blob|text|binary/ ) {
-               $col = "IF(`$col`='', '', CONCAT('0x', HEX(`$col`))) AS `$col`";
+               $col = "IF(BINARY(`$col`)='', '', CONCAT('0x', HEX(`$col`))) AS `$col`";
             }
             else {
                $col = "`$col`";
diff --git a/lib/ChangeHandler.pm b/lib/ChangeHandler.pm
index da0516ff..cbba6f66 100644
--- a/lib/ChangeHandler.pm
+++ b/lib/ChangeHandler.pm
@@ -488,7 +488,10 @@ sub make_fetch_back_query {
             my $col = $_;
             if (    $self->{hex_blob}
                  && $tbl_struct->{type_for}->{$col} =~ m/blob|text|binary/ ) {
-               $col = "IF(`$col`='', '', CONCAT('0x', HEX(`$col`))) AS `$col`";
+               # Here we cast to binary, as otherwise, since text columns are
+               # space padded, MySQL would compare ' ' and '' to be the same.
+               # See https://bugs.launchpad.net/percona-toolkit/+bug/930693
+               $col = "IF(BINARY(`$col`)='', '', CONCAT('0x', HEX(`$col`))) AS `$col`";
             }
             else {
                $col = "`$col`";
diff --git a/t/lib/ChangeHandler.t b/t/lib/ChangeHandler.t
index 835fdd31..2f7aa676 100644
--- a/t/lib/ChangeHandler.t
+++ b/t/lib/ChangeHandler.t
@@ -357,7 +357,7 @@ $ch = new ChangeHandler(
 
 is(
    $ch->make_fetch_back_query('1=1'),
-   "SELECT `a`, IF(`x`='', '', CONCAT('0x', HEX(`x`))) AS `x`, `b` FROM `test`.`lt` WHERE 1=1 LIMIT 1",
+   "SELECT `a`, IF(BINARY(`x`)='', '', CONCAT('0x', HEX(`x`))) AS `x`, `b` FROM `test`.`lt` WHERE 1=1 LIMIT 1",
    "Wraps BLOB column in CONCAT('0x', HEX(col)) AS col"
 );
 
@@ -402,7 +402,7 @@ $ch = new ChangeHandler(
 
 is(
    $ch->make_fetch_back_query('1=1'),
-   "SELECT IF(`t`='', '', CONCAT('0x', HEX(`t`))) AS `t` FROM `test`.`t` WHERE 1=1 LIMIT 1",
+   "SELECT IF(BINARY(`t`)='', '', CONCAT('0x', HEX(`t`))) AS `t` FROM `test`.`t` WHERE 1=1 LIMIT 1",
    "Don't prepend 0x to blank blob/text column value (issue 1052)"
 );