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Detect infinite loops using only lower boundaries.

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This commit is contained in:
Daniel Nichter
2011-09-26 08:53:22 -06:00
parent 4e8b00b4cc
commit eff835ffe7
2 changed files with 39 additions and 25 deletions
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62
lib/NibbleIterator.pm
View File

@@ -447,6 +447,29 @@ sub _next_boundaries {
return 1;
}
# Detect infinite loops. If the lower boundary we just nibbled from
# is identical to the next lower boundary, then this next nibble won't
# go anywhere, so to speak, unless perhaps the chunk size has changed
# which will cause us to nibble further ahead and maybe get a new lower
# boundary that isn't identical, but we can't detect this, and in any
# case, if there's one infinite loop there will probably be others.
if ( $self->_identical_boundaries($self->{lb}, $self->{next_lb}) ) {
MKDEBUG && _d('Infinite loop detected');
my $tbl = $self->{tbl};
my $index = $tbl->{tbl_struct}->{keys}->{$self->{index}};
my $n_cols = scalar @{$index->{cols}};
my $chunkno = $self->{nibbleno};
die "Possible infinite loop detected! "
. "The lower boundary for chunk $chunkno is "
. "<" . join(', ', @{$self->{lb}}) . "> and the lower "
. "boundary for chunk " . ($chunkno + 1) . " is also "
. "<" . join(', ', @{$self->{next_lb}}) . ">. "
. "This usually happens when using a non-unique single "
. "column index. The current chunk index for table "
. "$tbl->{db}.$tbl->{tbl} is $self->{index} which is"
. ($index->{is_unique} ? '' : ' not') . " unique and covers "
. ($n_cols > 1 ? "$n_cols columns" : "1 column") . ".\n";
}
$self->{lb} = $self->{next_lb};
MKDEBUG && _d($self->{ub_sth}->{Statement}, 'params:',
@@ -457,22 +480,6 @@ sub _next_boundaries {
if ( $boundary && @$boundary ) {
$self->{ub} = $boundary->[0]; # this nibble
if ( $boundary->[1] ) {
if ( $self->_identical_boundaries($boundary) ) {
my $tbl = $self->{tbl};
my $index = $tbl->{tbl_struct}->{keys}->{$self->{index}};
my $n_cols = scalar @{$index->{cols}};
my $chunkno = $self->{nibbleno} + 1;
die "Possible infinite loop detected! "
. "The upper boundary for chunk $chunkno is "
. "<" . join(', ', @{$boundary->[0]}) . "> and the lower "
. "boundary for chunk " . ($chunkno + 1) . " is also "
. "<" . join(', ', @{$boundary->[1]}) . ">. "
. "This usually happens when using a non-unique single "
. "column index. The current chunk index for table "
. "$tbl->{db}.$tbl->{tbl} is $self->{index} which is"
. ($index->{is_unique} ? '' : ' not') . " unique and covers "
. ($n_cols > 1 ? "$n_cols columns" : "1 column") . ".\n";
}
$self->{next_lb} = $boundary->[1]; # next nibble
}
else {
@@ -491,16 +498,23 @@ sub _next_boundaries {
}
sub _identical_boundaries {
my ($self, $boundaries) = @_;
my $ub = $boundaries->[0];
my $lb = $boundaries->[1];
return 0 unless $ub && $lb;
my $n_vals = scalar @$ub;
my ($self, $b1, $b2) = @_;
# If only one boundary isn't defined, then they can't be identical.
return 0 if ($b1 && !$b2) || (!$b1 && $b2);
# If both boundaries aren't defined, then they're identical.
return 1 if !$b1 && !$b2;
# Both boundaries are defined; compare their values and return false
# on the fisrt difference because only one diff is needed to prove
# that they're not identical.
die "Boundaries have different numbers of values"
if scalar @$b1 != scalar @$b2; # shouldn't happen
my $n_vals = scalar @$b1;
for my $i ( 0..($n_vals-1) ) {
# One diff means the bounds aren't identical.
return 0 if $lb->[$i] ne $ub->[$i];
return 0 if $b1->[$i] ne $b2->[$i]; # diff
}
MKDEBUG && _d('Infinite loop detected');
return 1;
}

2
t/lib/NibbleIterator.t
View File

@@ -503,7 +503,7 @@ $dbh->do('alter table bad_tables.inv drop index index_inv_on_tee_id_and_on_id');
$ni = make_nibble_iter(
db => 'bad_tables',
tbl => 'inv',
argv => [qw(--databases bad_tables --chunk-size 7)],
argv => [qw(--databases bad_tables --chunk-size 3)],
);
is(