Test and fix parsing literal backticks in TableParser:parse() (lp 1462904).

lib/TableParser.pm

@@ -163,6 +163,12 @@ sub parse {
    my (%type_for, %is_nullable, %is_numeric, %is_autoinc);
    foreach my $col ( @cols ) {
       my $def = $def_for{$col};
+
+      # Remove literal backticks (``) because they're superfluous for parsing
+      # the col.
+      # https://bugs.launchpad.net/percona-toolkit/+bug/1462904
+      $def =~ s/``//g;
+
       my ( $type ) = $def =~ m/`[^`]+`\s([a-z]+)/;
       die "Can't determine column type for $def" unless $type;
       $type_for{$col} = $type;

t/lib/TableParser.t

@@ -964,6 +964,40 @@ ok(
 
 diag(`$trunk/sandbox/stop-sandbox $master3_port >/dev/null`);
 
+# #############################################################################
+# pt-duplicate-key-checker doesn't support triple quote in column name
+# https://bugs.launchpad.net/percona-toolkit/+bug/1462904
+# #############################################################################
+
+$tbl = $tp->parse(load_file('t/lib/samples/triple-quoted-col.sql'));
+is_deeply(
+   $tbl,
+   {
+      clustered_key  => undef,
+      col_posn       => { 'foo' => 0, bar => 1  },
+      cols           => [ 'foo', 'bar' ],
+      defs           => {
+         'foo' => '  `foo` int(11) DEFAULT NULL',
+         'bar' => '  ```bar``` int(11) DEFAULT NULL',
+      },
+      engine         => 'InnoDB',
+      is_autoinc     => { foo => 0, bar => 0 },
+      is_col         => { foo => 1, bar  => 1 },
+      is_nullable    => { foo => 1, bar => 1 },
+      is_numeric     => { foo => 1, bar => 1 },
+      name           => 't',
+      null_cols      => [ 'foo', 'bar' ],
+      numeric_cols   => [ 'foo', 'bar' ],
+      type_for       => {
+         foo => 'int',
+         bar => 'int',
+      },
+      keys    => {},
+      charset => undef,
+   },
+   'Literal backticks (bug 1462904)'
+);
+
 # #############################################################################
 # Done.
 # #############################################################################

t/lib/samples/triple-quoted-col.sql

@@ -0,0 +1,4 @@
+CREATE TABLE `t` (
+  `foo` int(11) DEFAULT NULL,
+  ```bar``` int(11) DEFAULT NULL
+) ENGINE=InnoDB