$pea   = $database_adaptor->get_PredictionExonAdaptor();
  $pexon = $pea->fetch_by_dbID();

  my $slice =
    $database_adaptor->get_SliceAdaptor->fetch_by_region( 'X', 1, 1e6 );

  my @pexons = @{ $pea->fetch_all_by_Slice($slice) };

  my $self = shift;

  return qw( pe.prediction_exon_id
             pe.seq_region_id
             pe.seq_region_start
             pe.seq_region_end
             pe.seq_region_strand
             pe.start_phase
             pe.score
             pe.p_value );
}


# _final_clause
#
#  Arg [1]    : none
#  Example    : none
#  Description: PROTECTED implementation of superclass abstract method
#               returns a default end for the SQL-query (ORDER BY)
#  Returntype : string
#  Exceptions : none
#  Caller     : internal

  return "ORDER BY pe.prediction_transcript_id, pe.exon_rank";

  my ($self, $sth, $mapper, $dest_slice) = @_;

  #
  # This code is ugly because an attempt has been made to remove as many
  # function calls as possible for speed purposes.  Thus many caches and
  # a fair bit of gymnastics is used.
  #
  my $sa = $self->db()->get_SliceAdaptor();

  my @exons;
  my %slice_hash;
  my %sr_name_hash;
  my %sr_cs_hash;

  my($prediction_exon_id,$seq_region_id,
     $seq_region_start, $seq_region_end, $seq_region_strand,
     $start_phase, $score, $p_value);

  $sth->bind_columns(\$prediction_exon_id,\$seq_region_id,\$
     seq_region_start,\$ seq_region_end,\$ seq_region_strand,\$
     start_phase,\$ score,\$ p_value);

  my $asm_cs;
  my $cmp_cs;
  my $asm_cs_vers;
  my $asm_cs_name;
  my $cmp_cs_vers;
  my $cmp_cs_name;
  if($mapper) {
    $asm_cs = $mapper->assembled_CoordSystem();
    $cmp_cs = $mapper->component_CoordSystem();
    $asm_cs_name = $asm_cs->name();
    $asm_cs_vers = $asm_cs->version();
    $cmp_cs_name = $cmp_cs->name();
    $cmp_cs_vers = $cmp_cs->version();
  }

  my $dest_slice_start;
  my $dest_slice_end;
  my $dest_slice_strand;
  my $dest_slice_length;
  my $dest_slice_cs;
  my $asma;
  my $dest_slice_sr_name;
  my $dest_slice_sr_id;
 
  if($dest_slice) {
    $dest_slice_start  = $dest_slice->start();
    $dest_slice_end    = $dest_slice->end();
    $dest_slice_strand = $dest_slice->strand();
    $dest_slice_length = $dest_slice->length();
    $dest_slice_cs = $dest_slice->coord_system;
    $dest_slice_sr_name = $dest_slice->seq_region_name();
    $dest_slice_sr_id =  $dest_slice->get_seq_region_id();
    $asma = $self->db->get_AssemblyMapperAdaptor();
  }

  FEATURE: while($sth->fetch()) {
    #need to get the internal_seq_region, if present
    $seq_region_id = $self->get_seq_region_id_internal($seq_region_id);
    my $slice = $slice_hash{"ID:".$seq_region_id};
    my $dest_mapper = $mapper;


    if(!$slice) {
      $slice = $sa->fetch_by_seq_region_id($seq_region_id);
      $slice_hash{"ID:".$seq_region_id} = $slice;
      $sr_name_hash{$seq_region_id} = $slice->seq_region_name();
      $sr_cs_hash{$seq_region_id} = $slice->coord_system();
    }

    #obtain a mapper if none was defined, but a dest_seq_region was
    if(!$dest_mapper && $dest_slice && 
       !$dest_slice_cs->equals($slice->coord_system)) {
      $dest_mapper = $asma->fetch_by_CoordSystems($dest_slice_cs,
                                                 $slice->coord_system);
      $asm_cs = $dest_mapper->assembled_CoordSystem();
      $cmp_cs = $dest_mapper->component_CoordSystem();
      $asm_cs_name = $asm_cs->name();
      $asm_cs_vers = $asm_cs->version();
      $cmp_cs_name = $cmp_cs->name();
      $cmp_cs_vers = $cmp_cs->version();
    }

    my $sr_name = $sr_name_hash{$seq_region_id};
    my $sr_cs   = $sr_cs_hash{$seq_region_id};
  
    #
    # remap the feature coordinates to another coord system 
    # if a mapper was provided
    #
    if($dest_mapper) {

      ($seq_region_id,$seq_region_start,$seq_region_end,$seq_region_strand) =
        $dest_mapper->fastmap($sr_name, $seq_region_start, $seq_region_end,
                              $seq_region_strand, $sr_cs);

      #skip features that map to gaps or coord system boundaries
      next FEATURE if(!defined($seq_region_id));

      #get a slice in the coord system we just mapped to
#      if($asm_cs == $sr_cs || ($cmp_cs != $sr_cs && $asm_cs->equals($sr_cs))) {
        $slice = $slice_hash{"ID:".$seq_region_id} ||=
          $sa->fetch_by_seq_region_id($seq_region_id);
#      } else {
#        $slice = $slice_hash{"NAME:$sr_name:$asm_cs_name:$asm_cs_vers"} ||=
#          $sa->fetch_by_region($asm_cs_name, $sr_name, undef, undef, undef,
#                               $asm_cs_vers);
#      }
    } 

    #
    # If a destination slice was provided convert the coords
    # If the dest_slice starts at 1 and is foward strand, nothing needs doing
    #
    if($dest_slice) {
      if($dest_slice_start != 1 || $dest_slice_strand != 1) {
	if($dest_slice_strand == 1) {
	  $seq_region_start = $seq_region_start - $dest_slice_start + 1;
	  $seq_region_end   = $seq_region_end   - $dest_slice_start + 1;
	} else {
	  my $tmp_seq_region_start = $seq_region_start;
	  $seq_region_start = $dest_slice_end - $seq_region_end + 1;
	  $seq_region_end   = $dest_slice_end - $tmp_seq_region_start + 1;
	  $seq_region_strand *= -1;
	}
      }

      #throw away features off the end of the requested slice
      if($seq_region_end < 1 || $seq_region_start > $dest_slice_length ||
	 ( $dest_slice_sr_id ne $seq_region_id )) {
	next FEATURE;
      }
      
      $slice = $dest_slice;
    }

    # Finally, create the new PredictionExon.
    push( @exons,
          $self->_create_feature( 'Bio::EnsEMBL::PredictionExon', {
                                    '-start'   => $seq_region_start,
                                    '-end'     => $seq_region_end,
                                    '-strand'  => $seq_region_strand,
                                    '-adaptor' => $self,
                                    '-slice'   => $slice,
                                    '-dbID'    => $prediction_exon_id,
                                    '-phase'   => $start_phase,
                                    '-score'   => $score,
                                    '-p_value' => $p_value
                                  } ) );

  }

  return\@ exons;
}


1;

  return ([ 'prediction_exon', 'pe' ] );
}



#_columns
#
#  Arg [1]    : none
#  Example    : none
#  Description: PROTECTED implementation of superclass abstract method
#               returns a list of columns to use for queries
#  Returntype : list of strings
#  Exceptions : none
#  Caller     : internal

  my ( $self, $transcript ) = @_;
  my $constraint = "pe.prediction_transcript_id = ".$transcript->dbID();

  # use 'keep_all' option to keep exons that are off end of slice

  my $tslice = $transcript->slice();
  my $slice;

  if(!$tslice) {
    throw("Transcript must have attached slice to retrieve exons.");
  }

  # use a small slice the same size as the prediction transcript
  $slice = $self->db->get_SliceAdaptor->fetch_by_Feature($transcript);

  my $exons = $self->fetch_all_by_Slice_constraint($slice, $constraint);

  # remap exon coordinates if necessary
  if($slice->name() ne $tslice->name()) {
    my @out;
    foreach my $ex (@$exons) {
      push @out, $ex->transfer($tslice);
    }
    $exons =\@ out;
  }

  return $exons;

   my ($self,$ordered) = @_;

   return $self->_list_dbIDs("prediction_exon",undef, $ordered);
}



#_objs_from_sth

#  Arg [1]    : Hashreference $hashref
#  Example    : none 
#  Description: PROTECTED implementation of abstract superclass method.
#               responsible for the creation of Genes 
#  Returntype : listref of Bio::EnsEMBL::Genes in target coordinate system
#  Exceptions : none
#  Caller     : internal
#

  my $self = shift;
  my $pexon = shift;

  my $db = $self->db();

  if(!$pexon->is_stored($db)) {
    warning('PredictionExon is not in this DB - not removing');
    return undef;
  }

  my $sth = $self->prepare(
            "DELETE FROM prediction_exon WHERE prediction_exon_id = ?");
  $sth->bind_param( 1, $pexon->dbID, SQL_INTEGER );
  $sth->execute();

  $pexon->dbID(undef);
  $pexon->adaptor(undef);

  my ( $self, $pexon, $pt_id, $rank ) = @_;

  if(!ref($pexon) || !$pexon->isa('Bio::EnsEMBL::PredictionExon') ) {
    throw("Expected PredictionExon argument");
  }

  throw("Expected PredictionTranscript id argument.") if(!$pt_id);
  throw("Expected rank argument.") if(!$rank);

  my $db = $self->db();

  if($pexon->is_stored($db)) {
    warning('PredictionExon is already stored in this DB.');
    return $pexon->dbID();
  }

  if( ! $pexon->start || ! $pexon->end ||
      ! $pexon->strand || ! defined $pexon->phase ) {
    throw("PredictionExon does not have all attributes to store.\n" .
         "start, end, strand and phase attributes must be set.");
  }

  #maintain reference to original passed-in prediction exon
  my $original = $pexon;
  my $seq_region_id;
  ($pexon, $seq_region_id) = $self->_pre_store($pexon);

  my $sth = $db->dbc->prepare
    ("INSERT into prediction_exon (prediction_transcript_id, exon_rank, " .
                       "seq_region_id, seq_region_start, seq_region_end, " .
                       "seq_region_strand, start_phase, score, p_value) " .
      "VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ? )");

  $sth->bind_param(1,$pt_id,SQL_INTEGER);
  $sth->bind_param(2,$rank,SQL_SMALLINT);
  $sth->bind_param(3,$seq_region_id,SQL_INTEGER);
  $sth->bind_param(4,$pexon->start,SQL_INTEGER);
  $sth->bind_param(5,$pexon->end,SQL_INTEGER);
  $sth->bind_param(6,$pexon->strand,SQL_TINYINT);
  $sth->bind_param(7,$pexon->phase,SQL_TINYINT);
  $sth->bind_param(8,$pexon->score,SQL_DOUBLE);
  $sth->bind_param(9,$pexon->p_value,SQL_DOUBLE);

  $sth->execute();

  my $dbID = $sth->{'mysql_insertid'};

  #set the adaptor and dbID of the object they passed in
  $original->dbID($dbID);
  $original->adaptor($self);

  return $dbID;

  Copyright (c) 1999-2009 The European Bioinformatics Institute and
  Genome Research Limited.  All rights reserved.

  This software is distributed under a modified Apache license.
  For license details, please see

    /info/about/code_licence.html

  Please email comments or questions to the public Ensembl
  developers list at <ensembl-dev@ebi.ac.uk>.

  Questions may also be sent to the Ensembl help desk at
  <helpdesk@ensembl.org>.