SQLite::VirtualTable::Pivot::Cursor - a cursor for a pivot table query

SQLite-VirtualTable-Pivot documentation Contained in the SQLite-VirtualTable-Pivot distribution.

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NAME

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SQLite::VirtualTable::Pivot::Cursor - a cursor for a pivot table query

DESCRIPTION

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Objects in this class represent cursors for queries on pivot tables.

They maintatin a statement handle corresponding to an unpivotted query on the base table. The pivotting operation is done one row at a time, as data is returned; i.e. we order by the id, and group on the fly.

It must be possible for multiple cursors to exist at once on the same pivot table, in case it occurs more than once in a query.

SEE ALSO

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SQLite::VirtualTable::Pivot

SQLite-VirtualTable-Pivot documentation Contained in the SQLite-VirtualTable-Pivot distribution. 
package SQLite::VirtualTable::Pivot::Cursor;

use base 'Class::Accessor::Contextual';
use Data::Dumper;

# State variables (probably could be simplified)
__PACKAGE__->mk_accessors(qw| first last done row_id queued |);
__PACKAGE__->mk_accessors(qw| sth current_row               |);

# list of temp tables
__PACKAGE__->mk_accessors(qw| temp_tables                   |);

# the virtual table to whom we belong
__PACKAGE__->mk_accessors(qw| virtual_table                 |);

sub debug($)  { return unless $ENV{DEBUG}; print STDERR "# $_[0]\n"; }

sub reset {
    my $self = shift;
    $self->set( first       => 1  );
    $self->set( done        => 0  );
    $self->set( queued      => {} );
    $self->set( "last"      => 0  );
    $self->set( current_row => [] );
    $self->set( last_row    => [] );
    $self->set( temp_tables => [] );
    return $self;
}

sub get_next_row {
  my $self = shift;
  $self->{queued}      = {};
  $self->{last_row}    ||= [];
  $self->{current_row} ||= [];
  return if $self->done;
  $self->{row_id}++;
  $self->{done} = $self->{last};
  my $row      = $self->{current_row};
  my $last_row = $self->{last_row};
  my $queued   = $self->{queued};
  $self->{last} = 0;
  while ($self->first || $self->virtual_table->_row_values_are_equal($row->[0],$last_row->[0])) {
    $self->set( first => 0 );
    if (@$row) {
        $queued->{ $row->[1] } = $row->[2];
        $queued->{$self->virtual_table->pivot_row} = $row->[0];
    }
    @$last_row = @$row;
    $self->{last} = !( @$row = $self->sth->fetchrow_array );
    last if $self->{last};
  }
  my $dumped = Dumper($self->queued);
  $dumped =~ s/\n|\s//g;
  debug "called next, queued is now $dumped ";
  @$last_row = @$row;
}

sub column_value {
    my $self = shift;
    my $column_name = shift;
    debug "column $column_name: $self->{queued}->{$column_name}";
    return $self->queued->{$column_name};
}

1;