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Handle resume in OobNibbleIterator.

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This commit is contained in:
Daniel Nichter
2011-11-16 11:10:34 -07:00
parent 27456d00b7
commit 42bd00c4d6
2 changed files with 61 additions and 17 deletions
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60
lib/NibbleIterator.pm
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@@ -133,21 +133,37 @@ sub new {
my $from = $q->quote(@{$tbl}{qw(db tbl)}) . " FORCE INDEX(`$index`)";
my $order_by = join(', ', map {$q->quote($_)} @{$index_cols});
# These statements are only executed once, so they don't use sths.
my $first_lb_where = $where ? "($where)" : '';
if ( $args{resume} ) {
$first_lb_where .= ($where ? " AND " : '') . $asc->{boundaries}->{'>'};
}
# The real first row in the table. Usually we start nibbling from
# this row. Called once in _get_bounds().
my $first_lb_sql
= "SELECT /*!40001 SQL_NO_CACHE */ "
. join(', ', map { $q->quote($_) } @{$asc->{scols}})
. " FROM $from"
. ($first_lb_where ? " WHERE $first_lb_where" : '')
. ($where ? " WHERE $where" : '')
. " ORDER BY $order_by"
. " LIMIT 1"
. " /*first lower boundary*/";
MKDEBUG && _d('First lower boundary statement:', $first_lb_sql);
# If we're resuming, this fetches the effective first row, which
# should differ from the real first row. Called once in _get_bounds().
my $resume_lb_sql;
if ( $args{resume} ) {
$resume_lb_sql
= "SELECT /*!40001 SQL_NO_CACHE */ "
. join(', ', map { $q->quote($_) } @{$asc->{scols}})
. " FROM $from"
. " WHERE " . $asc->{boundaries}->{'>'}
. ($where ? " AND ($where)" : '')
. " ORDER BY $order_by"
. " LIMIT 1"
. " /*resume lower boundary*/";
MKDEBUG && _d('Resume lower boundary statement:', $resume_lb_sql);
}
# The nibbles are inclusive, so we need to fetch the real last row
# in the table. Saved as boundary last_upper and used as boundary
# upper in some cases. Called once in _get_bounds().
my $last_ub_sql
= "SELECT /*!40001 SQL_NO_CACHE */ "
. join(', ', map { $q->quote($_) } @{$asc->{scols}})
@@ -218,6 +234,7 @@ sub new {
explain_ub_sql => "EXPLAIN $ub_sql",
explain_nibble_sql => $explain_nibble_sql,
resume => $args{resume},
resume_lb_sql => $resume_lb_sql,
sql => {
columns => $asc->{scols},
from => $from,
@@ -534,20 +551,33 @@ sub _get_bounds {
my $dbh = $self->{Cxn}->dbh();
# Get the real first lower boundary.
$self->{first_lower} = $dbh->selectrow_arrayref($self->{first_lb_sql});
MKDEBUG && _d('First lower boundary:', Dumper($self->{first_lower}));
# The next boundary is the first lower boundary. If resuming,
# this should be something > the real first lower boundary.
if ( my $nibble = $self->{resume} ) {
my $sth = $dbh->prepare($self->{first_lb_sql});
my @ub = split ',', $nibble->{upper_boundary};
MKDEBUG && _d($sth->{Statement}, 'params:', @ub);
$sth->execute(@ub);
$self->{first_lower} = $sth->fetchrow_arrayref();
$sth->finish();
if ( defined $nibble->{upper_boundary} ) {
my $sth = $dbh->prepare($self->{resume_lb_sql});
my @ub = split ',', $nibble->{upper_boundary};
MKDEBUG && _d($sth->{Statement}, 'params:', @ub);
$sth->execute(@ub);
$self->{next_lower} = $sth->fetchrow_arrayref();
$sth->finish();
}
else {
MKDEBUG && _d('No more boundaries to resume');
$self->{no_more_boundaries} = 1;
}
}
else {
$self->{first_lower} = $dbh->selectrow_arrayref($self->{first_lb_sql});
$self->{next_lower} = $self->{first_lower};
}
$self->{next_lower} = $self->{first_lower};
MKDEBUG && _d('First lower boundary:', Dumper($self->{next_lower}));
MKDEBUG && _d('Next lower boundary:', Dumper($self->{next_lower}));
# Get the real last upper boundary, i.e. the last row of the table
# at this moment. If rows are inserted after, we won't see them.
$self->{last_upper} = $dbh->selectrow_arrayref($self->{last_ub_sql});
MKDEBUG && _d('Last upper boundary:', Dumper($self->{last_upper}));