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https://github.com/percona/percona-toolkit.git
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Create NibbleIterator. Cleanup TableNibbler. Fix bug in SchemaIterator.
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Daniel Nichter
261
lib/NibbleIterator.pm
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261
lib/NibbleIterator.pm
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# This program is copyright 2011 Percona Inc.
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# Feedback and improvements are welcome.
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#
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# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
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# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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#
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# This program is free software; you can redistribute it and/or modify it under
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# the terms of the GNU General Public License as published by the Free Software
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# Foundation, version 2; OR the Perl Artistic License. On UNIX and similar
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# systems, you can issue `man perlgpl' or `man perlartistic' to read these
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# licenses.
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#
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# You should have received a copy of the GNU General Public License along with
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# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
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# Place, Suite 330, Boston, MA 02111-1307 USA.
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# ###########################################################################
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# NibbleIterator package
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# ###########################################################################
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{
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# Package: NibbleIterator
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# NibbleIterator nibbles tables.
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package NibbleIterator;
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use strict;
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use warnings FATAL => 'all';
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use English qw(-no_match_vars);
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use constant MKDEBUG => $ENV{MKDEBUG} || 0;
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use Data::Dumper;
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$Data::Dumper::Indent = 1;
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$Data::Dumper::Sortkeys = 1;
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$Data::Dumper::Quotekeys = 0;
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sub new {
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my ( $class, %args ) = @_;
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my @required_args = qw(dbh tbl OptionParser Quoter TableNibbler TableParser);
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foreach my $arg ( @required_args ) {
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die "I need a $arg argument" unless $args{$arg};
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}
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my ($dbh, $tbl, $o, $q) = @args{@required_args};
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# Get an index to nibble by. We'll order rows by the index's columns.
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my $index = $args{TableParser}->find_best_index(
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$tbl->{tbl_struct},
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$o->get('chunk-index'),
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);
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die "No index to nibble table $tbl->{db}.$tbl->{tbl}" unless $index;
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my $index_cols = $tbl->{tbl_struct}->{keys}->{$index}->{cols};
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# Figure out how to nibble the table with the index.
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my $asc = $args{TableNibbler}->generate_asc_stmt(
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%args,
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tbl_struct => $tbl->{tbl_struct},
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index => $index,
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asc_only => 1,
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);
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# Make SQL statements, prepared on first call to next(). The preamble
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# and ORDER BY are the same for all statements. FORCE IDNEX and ORDER BY
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# are needed to ensure deterministic nibbling.
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my $nibble_sql_preamble
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= "SELECT /*!40001 SQL_NO_CACHE */ "
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. join(', ', map { $q->quote($_) } @{$asc->{cols}})
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. " FROM " . $q->quote(@{$tbl}{qw(db tbl)})
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. " FORCE INDEX(`$index`)";
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my $order_by = "ORDER BY " . join(', ', map {$q->quote($_)} @{$index_cols});
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# This statement is only executed once, so it doesn't use a sth.
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my $first_lb_sql
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= $nibble_sql_preamble
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. ($args{where} ? " WHERE $args{where}" : '')
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. " $order_by "
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. " LIMIT 1"
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. " /*first lower boundary*/";
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MKDEBUG && _d('First lower boundary statement:', $first_lb_sql);
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# Nibbles are inclusive, so for a..z, the nibbles are: a-e, f-j, k-o, p-t,
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# u-y, and z. This complicates getting the next upper boundary because
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# if we use either (col >= lb AND col < ub) or (col > lb AND col <= ub)
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# in nibble_sql (below), then that fails for either the last or first
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# nibble respectively. E.g. (col >= z AND col < z) doesn't work, nor
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# does (col > a AND col <= e). Hence the fancy LIMIT 2 which returns
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# the upper boundary for the current nibble *and* the lower boundary
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# for the next nibble. See _next_boundaries().
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my $ub_sql
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= $nibble_sql_preamble
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. " WHERE (" . $asc->{boundaries}->{'>='} . ")" # lower boundary
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. ($args{where} ? " AND ($args{where})" : '')
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. " $order_by "
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. " LIMIT 2 OFFSET " . (($o->get('chunk-size') || 1) - 1)
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. " /*upper boundary*/";
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MKDEBUG && _d('Next upper boundary statement:', $ub_sql);
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my $nibble_sql
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= $nibble_sql_preamble
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. " WHERE (" . $asc->{boundaries}->{'>='} . ")" # lower boundary
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. " AND (" . $asc->{boundaries}->{'<='} . ")" # upper boundary
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. ($args{where} ? " AND ($args{where})" : '')
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. " $order_by"
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. " /*nibble*/";
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MKDEBUG && _d('Nibble statement:', $nibble_sql);
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my $self = {
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%args,
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asc => $asc,
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first_lb_sql => $first_lb_sql,
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ub_sql => $ub_sql,
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nibble_sql => $nibble_sql,
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nibbleno => 0,
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have_rows => 0,
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rowno => 0,
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};
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return bless $self, $class;
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}
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sub next {
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my ($self) = @_;
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# First call, init everything. This could be done in new(), but
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# all work is delayed until actually needed.
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if ($self->{nibbleno} == 0) {
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$self->_prepare_sths();
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$self->_get_first_lb();
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# $self->_check_index_usage();
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}
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# Return rows in nibble. sth->{Active} is always true with DBD::mysql v3,
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# so we track the status manually. have_rows will be true if a previous
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# call got a nibble with rows. When there's no more rows in this nibble,
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# try to get the next nibble.
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if ( $self->{have_rows} ) {
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my $row = $self->{nibble_sth}->fetchrow_arrayref();
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if ( $row ) {
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$self->{rowno}++;
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MKDEBUG && _d('Row', $self->{rowno}, 'in nibble', $self->{nibbleno});
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# fetchrow_arraryref re-uses its internal arrayref, so we must copy.
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return [ @$row ];
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}
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MKDEBUG && _d('No more rowso in nibble', $self->{nibbleno});
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$self->{rowno} = 0;
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$self->{have_rows} = 0;
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}
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# If there's another boundary, fetch the rows within it.
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if ( $self->_next_boundaries() ) {
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MKDEBUG && _d($self->{nibble_sth}->{Statement}, 'params:',
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join(', ', (@{$self->{lb}}, @{$self->{ub}})));
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$self->{nibble_sth}->execute(@{$self->{lb}}, @{$self->{ub}});
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$self->{have_rows} = $self->{nibble_sth}->rows();
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if ( $self->{have_rows} ) {
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$self->{nibbleno}++;
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MKDEBUG && _d($self->{have_rows}, 'rows in nibble', $self->{nibbleno});
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return $self->next();
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}
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}
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MKDEBUG && _d('Done nibbling');
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return;
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}
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sub _prepare_sths {
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my ($self) = @_;
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MKDEBUG && _d('Preparing statement handles');
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$self->{ub_sth} = $self->{dbh}->prepare($self->{ub_sql});
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$self->{nibble_sth} = $self->{dbh}->prepare($self->{nibble_sql});
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}
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sub _get_first_lb {
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my ($self) = @_;
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$self->{next_lb} = $self->{dbh}->selectrow_arrayref($self->{first_lb_sql});
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MKDEBUG && _d('First lower boundary:', Dumper($self->{lb}));
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return;
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}
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sub _check_index_usage {
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my ($self) = @_;
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my ($dbh, $tbl, $q) = @{$self}{qw(dbh tbl Quoter)};
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my $table_status;
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eval {
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my $sql = "SHOW TABLE STATUS FROM " . $q->quote($tbl->{db})
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. " LIKE " . $q->literal_like($tbl->{tbl});
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MKDEBUG && _d($sql);
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$table_status = $dbh->selectrow_hashref($sql);
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};
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MKDEBUG && $EVAL_ERROR && _d($EVAL_ERROR);
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my $small_table;
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if ( $table_status ) {
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my $n_rows = defined $table_status->{Rows} ? $table_status->{Rows}
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: defined $table_status->{rows} ? $table_status->{rows}
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: undef;
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$small_table = 1 if defined $n_rows && $n_rows <= 100;
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}
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MKDEBUG && _d('Small table:', $small_table);
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if ( !$small_table ) {
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my $explain;
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eval {
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$explain = $dbh->selectall_arrayref("", {Slice => {}});
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};
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if ( $EVAL_ERROR ) {
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MKDEBUG && _d($EVAL_ERROR);
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return;
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}
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MKDEBUG && _d('EXPLAIN key:', $explain->[0]->{key});
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my $explain_index = lc($explain->[0]->{key} || '');
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if ( $explain_index ne lc($self->{asc}->{index}) ) {
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die "Cannot nibble table $tbl->{db}.$tbl->{tbl} because MySQL chose "
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. ($explain_index ? "the `$explain_index`" : 'no') . ' index'
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. " instead of the `$self->{asc}->{index}` index";
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}
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}
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return;
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}
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sub _next_boundaries {
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my ($self) = @_;
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if ( $self->{no_more_boundaries} ) {
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MKDEBUG && _d('No more boundaries');
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return;
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}
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$self->{lb} = $self->{next_lb};
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MKDEBUG && _d($self->{ub_sth}->{Statement}, 'params:',
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join(', ', @{$self->{lb}}));
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$self->{ub_sth}->execute(@{$self->{lb}});
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my $boundary = $self->{ub_sth}->fetchall_arrayref();
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if ( $boundary && @$boundary ) {
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$self->{ub} = $boundary->[0]; # this nibble
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$self->{next_lb} = $boundary->[1]; # next nibble
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$self->{ub_sth}->finish();
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MKDEBUG && _d('Next upper boundary:', Dumper($self->{ub}));
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}
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else {
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$self->{no_more_boundaries} = 1; # for next call
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$self->{ub} = $self->{lb};
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MKDEBUG && _d('Last upper boundary:', Dumper($self->{ub}));
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}
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return 1; # have boundaries
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}
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sub _d {
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my ($package, undef, $line) = caller 0;
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@_ = map { (my $temp = $_) =~ s/\n/\n# /g; $temp; }
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map { defined $_ ? $_ : 'undef' }
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@_;
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print STDERR "# $package:$line $PID ", join(' ', @_), "\n";
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}
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1;
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}
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# ###########################################################################
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# End NibbleIterator package
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# ###########################################################################
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