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Alzabo

package Alzabo::SQLMaker;

use strict;
use vars qw($VERSION $AUTOLOAD);

use Alzabo::Exceptions;
use Alzabo::Utils;

use Class::Factory::Util;
use Params::Validate qw( :all );
Params::Validate::validation_options( on_fail => sub { Alzabo::Exception::Params->throw( error => join '', @_ ) } );

$VERSION = 2.0;

1;

sub make_function
{
    my $class = caller;

    my %p =
	validate( @_,
		  { function => { type => SCALAR },
		    min => { type => SCALAR, optional => 1 },
		    max => { type => UNDEF | SCALAR, optional => 1 },
		    groups => { type => ARRAYREF },
		    quote => { type => ARRAYREF, optional => 1 },
		    format => { type => SCALAR, optional => 1 },
		    is_modifier => { type => SCALAR, default => 0 },
		    has_spaces => { type => SCALAR, default => 0 },
		    allows_alias => { type => SCALAR, default => 1 },
		    no_parens => { type => SCALAR, default => 0 },
		  } );

    my $valid = '';
    if ( $p{min} || $p{max} )
    {
	$valid .= 'validate_pos( @_, ';
	$valid .= join ', ', ('1') x $p{min};
    }

    if ( defined $p{min} && defined $p{max} && $p{max} > $p{min} )
    {
	$valid .= ', ';
	$valid .= join ', ', ('0') x ( $p{max} - $p{min} );
    }
    elsif ( exists $p{min} && ! defined $p{max} )
    {
	$valid .= ", ('1') x (\@_ - $p{min})";
    }
    $valid .= ' );' if $valid;

    my @args = "function => '$p{function}'";

    if ( ! defined $p{max} || $p{max} > 0 )
    {
	push @args, '                                      args => [@_]';
    }

    if ( $p{format} )
    {
	push @args, "                                      format => '$p{format}'";
    }

    if ( $p{quote} )
    {
	my $quote .= '                                     quote => [';
	$quote .= join ', ', @{ $p{quote} };
	$quote .= ']';
	push @args, $quote;
    }

    for my $k ( qw( is_modifier has_spaces allows_alias no_parens ) )
    {
        if ( $p{$k} )
        {
            push @args, "                                      $k => 1";
        }
    }

    my $args = join ",\n", @args;

    my $code = <<"EOF";
sub ${class}::$p{function}
{
    shift if defined \$_[0] && Alzabo::Utils::safe_isa( \$_[0], 'Alzabo::SQLMaker' );
    $valid
    return Alzabo::SQLMaker::Function->new( $args );
}
EOF

    eval $code;

    {
	no strict 'refs';
	push @{ "$class\::EXPORT_OK" }, $p{function};
	my $exp = \%{ "$class\::EXPORT_TAGS" };
	foreach ( @{ $p{groups} } )
	{
	    push @{ $exp->{$_}  }, $p{function};
	}
	push @{ $exp->{all} }, $p{function};
    }
}

sub load
{
    shift;
    my %p = @_;

    my $class = "Alzabo::SQLMaker::$p{rdbms}";
    eval "use $class";
    Alzabo::Exception::Eval->throw( error => $@ ) if $@;

    $class->init(@_);

    return $class;
}

sub available { __PACKAGE__->subclasses }

sub init
{
    1;
}

use constant NEW_SPEC => { driver => { isa => 'Alzabo::Driver' },
                           quote_identifiers  => { type => BOOLEAN,
                                                   default => 0 },
                         };

sub new
{
    my $class = shift;
    my %p = validate( @_, NEW_SPEC );

    return bless { last_op => undef,
		   expect => undef,
		   type => undef,
		   sql => '',
		   bind => [],
		   placeholders => [],
		   as_id => 'aaaaa10000',
                   alias_in_having => 1,
                   %p,
		 }, $class;
}

# this just needs to be some unique thing that won't ever look like a
# valid bound parameter
my $placeholder = do { my $x = 1; bless \$x, 'Alzabo::SQLMaker::Placeholder' };
sub placeholder { $placeholder }

sub last_op
{
    return shift->{last_op};
}

sub select
{
    my $self = shift;

    Alzabo::Exception::Params->throw( error => "The select method requires at least one parameter" )
	unless @_;

    $self->{sql} .= 'SELECT ';

    if ( lc $_[0] eq 'distinct' )
    {
	$self->{sql} .= ' DISTINCT ';
	shift;
    }

    my @sql;
    foreach my $elt (@_)
    {
	if ( Alzabo::Utils::safe_can( $elt, 'table' ) )
	{
            my $table = $elt->table;

	    $self->{column_tables}{"$table"} = 1;

            my $sql =
                ( $self->{quote_identifiers} ?
                  $self->{driver}->quote_identifier
                      ( $table->alias_name, $elt->name ) :
                  $table->alias_name . '.' . $elt->name );

            $sql .= ' AS ' .
                ( $self->{quote_identifiers} ?
                  $self->{driver}->quote_identifier( $elt->alias_name ) :
                  $elt->alias_name );

	    push @sql, $sql;
	}

lib/Alzabo/SQLMaker.pm view on Meta::CPAN

                my $sql =
                    ( $self->{quote_identifiers} ?
                      $self->{driver}->quote_identifier
                      ( $elt->alias_name, $col->name ) :
                      $elt->alias_name . '.' . $col->name );

                $sql .= ' AS ' .
                    ( $self->{quote_identifiers} ?
                      $self->{driver}->quote_identifier( $elt->alias_name ) :
                      $elt->alias_name );

                push @cols, $sql;
            }

	    push @sql, join ', ', @cols;
	}
	elsif ( Alzabo::Utils::safe_isa( $elt, 'Alzabo::SQLMaker::Function' ) )
	{
	    my $string = $elt->as_string( $self->{driver}, $self->{quote_identifiers} );

	    if ( $elt->allows_alias )
	    {
		push @sql, " $string AS " . $self->{as_id};
		$self->{functions}{$string} = $self->{as_id};
		++$self->{as_id};
	    }
	    else
	    {
		push @sql, $string;
	    }
	}
	elsif ( ! ref $elt )
	{
	    push @sql, $elt;
	}
	else
	{
	    Alzabo::Exception::SQL->throw
                    ( error => 'Arguments to select must be either column objects,' .
                               ' table objects, function objects, or plain scalars' );
	}
    }

    $self->{sql} .= join ', ', @sql;

    $self->{type} = 'select';
    $self->{last_op} = 'select';

    return $self;
}

sub from
{
    my $self = shift;

    $self->_assert_last_op( qw( select delete function ) );

    my $spec =
        $self->{last_op} eq 'select' ? { type => OBJECT | ARRAYREF } : { can => 'alias_name' };

    validate_pos( @_, ( $spec ) x @_ );

    $self->{sql} .= ' FROM ';

    if ( $self->{last_op} eq 'delete' )
    {
	$self->{sql} .=
	    join ', ', map { ( $self->{quote_identifiers} ?
                               $self->{driver}->quote_identifier( $_->name ) :
                               $_->name ) } @_;

	$self->{tables} = { map { $_ => 1 } @_ };
    }
    else
    {
        my $sql;

	$self->{tables} = {};

        my @plain;
	foreach my $elt (@_)
	{
	    if ( Alzabo::Utils::is_arrayref($elt) )
	    {
		$sql .= ' ' if $sql;

                $sql .= $self->_outer_join(@$elt);
	    }
            else
            {
                push @plain, $elt;
            }
        }

        foreach my $elt ( grep { ! exists $self->{tables}{$_ } } @plain )
        {
            $sql .= ', ' if $sql;

            if ( $self->{quote_identifiers} )
            {
                $sql .=
                    ( $self->{driver}->quote_identifier( $elt->name ) .
                      ' AS ' .
                      $self->{driver}->quote_identifier( $elt->alias_name ) );
            }
            else
            {
                $sql .= $elt->name . ' AS ' . $elt->alias_name;
            }

            $self->{tables}{$elt} = 1;
	}

        $self->{sql} .= $sql;
    }

    if ($self->{type} eq 'select')
    {
        foreach my $t ( keys %{ $self->{column_tables} } )
        {
	    unless ( $self->{tables}{$t} )
	    {
		my $err = 'Cannot select column ';
		$err .= 'unless its table is included in the FROM clause';
		Alzabo::Exception::SQL->throw( error => $err );
	    }
	}
    }

    $self->{last_op} = 'from';

    return $self;
}

use constant _OUTER_JOIN_SPEC => ( { type => SCALAR },
                                   ( { can => 'alias_name' } ) x 2,
                                   { type => UNDEF | ARRAYREF | OBJECT, optional => 1 },
                                   { type => UNDEF | ARRAYREF, optional => 1 },
                                 );

sub _outer_join
{
    my $self = shift;

    my $tables = @_ - 1;
    validate_pos( @_, _OUTER_JOIN_SPEC );

    my $type = uc shift;

    my $join_from = shift;
    my $join_on = shift;
    my $fk;
    $fk = shift if $_[0] && Alzabo::Utils::safe_isa( $_[0], 'Alzabo::ForeignKey' );
    my $where = shift;

    unless ($fk)
    {
	my @fk = $join_from->foreign_keys_by_table($join_on);

	Alzabo::Exception::Params->throw( error => "The " . $join_from->name . " table has no foreign keys to the " . $join_on->name . " table" )
	    unless @fk;

	Alzabo::Exception::Params->throw( error => "The " . $join_from->name . " table has more than 1 foreign key to the " . $join_on->name . " table" )
	    if @fk > 1;

	$fk = $fk[0];
    }

    my $sql;
    unless ( $self->{tables}{$join_from} )
    {
        $sql .=
            ( $self->{quote_identifiers} ?
              $self->{driver}->quote_identifier( $join_from->name ) :
              $join_from->name );

        $sql .= ' AS ';
        $sql .=
            ( $self->{quote_identifiers} ?
              $self->{driver}->quote_identifier( $join_from->alias_name ) :
              $join_from->alias_name );
    }

    $sql .= " $type OUTER JOIN ";

    $sql .= ( $self->{quote_identifiers} ?
              $self->{driver}->quote_identifier( $join_on->name ) :
              $join_on->name );

    $sql .= ' AS ';

    $sql .=
        ( $self->{quote_identifiers} ?
          $self->{driver}->quote_identifier( $join_on->alias_name ) :
          $join_on->alias_name );

    $sql .= ' ON ';

    if ( $self->{quote_identifiers} )
    {
        $sql .=
            ( join ' AND ',
              map { $self->{driver}->quote_identifier
                        ( $join_from->alias_name, $_->[0]->name ) .
                    ' = ' .
                    $self->{driver}->quote_identifier

lib/Alzabo/SQLMaker.pm view on Meta::CPAN


sub or
{
    my $self = shift;

    $self->_assert_last_op( qw( subgroup_end condition ) );

    return $self->_and_or( 'or', @_ );
}

sub _and_or
{
    my $self = shift;
    my $op = shift;

    $self->{sql} .= " \U$op ";

    $self->{last_op} = $op;

    $self->condition(@_) if @_;

    return $self;
}

sub subgroup_start
{
    my $self = shift;

    $self->_assert_last_op( qw( where having and or subgroup_start ) );

    $self->{sql} .= ' (';
    $self->{subgroup} ||= 0;
    $self->{subgroup}++;

    $self->{last_op} = 'subgroup_start';

    return $self;
}

sub subgroup_end
{
    my $self = shift;

    $self->_assert_last_op( qw( condition subgroup_end ) );

    Alzabo::Exception::SQL->throw( error => "Can't end a subgroup unless one has been started already" )
	unless $self->{subgroup};

    $self->{sql} .= ' )';
    $self->{subgroup}--;

    $self->{last_op} = $self->{subgroup} ? 'subgroup_end' : 'condition';

    return $self;
}

sub condition
{
    my $self = shift;

    validate_pos( @_,
		  { type => OBJECT },
		  { type => SCALAR },
		  { type => UNDEF | SCALAR | OBJECT },
		  ( { type => UNDEF | SCALAR | OBJECT, optional => 1 } ) x (@_ - 3) );

    my $lhs = shift;
    my $comp = uc shift;
    my $rhs = shift;

    my $in_having = $self->{last_op} eq 'having' ? 1 : 0;

    $self->{last_op} = 'condition';

    if ( $lhs->can('table') && $lhs->can('name') )
    {
	unless ( $self->{tables}{ $lhs->table } )
	{
	    my $err = 'Cannot use column (';
	    $err .= join '.', $lhs->table->name, $lhs->name;
	    $err .= ") in $self->{type} unless its table is included in the ";
	    $err .= $self->{type} eq 'update' ? 'UPDATE' : 'FROM';
	    $err .= ' clause';
	    Alzabo::Exception::SQL->throw( error => $err );
	}

	$self->{sql} .=
	    ( $self->{quote_identifiers} ?
              $self->{driver}->quote_identifier( $lhs->table->alias_name, $lhs->name ) :
              $lhs->table->alias_name . '.' . $lhs->name );
    }
    elsif ( $lhs->isa('Alzabo::SQLMaker::Function') )
    {
	my $string = $lhs->as_string( $self->{driver}, $self->{quote_identifiers} );

        if ( exists $self->{functions}{$string} &&
             ( ! $in_having || $self->{alias_in_having} ) )
        {
            $self->{sql} .= $self->{functions}{$string};
        }
        else
        {
            $self->{sql} .= $string;
        }
    }
    else
    {
        Alzabo::Exception::SQL->throw
            ( error => "Cannot use " . (ref $lhs) . " object as part of condition" );
    }

    if ( $comp eq 'BETWEEN' )
    {
	Alzabo::Exception::SQL->throw
	    ( error => "The BETWEEN comparison operator requires an additional argument" )
		unless @_ == 1;

	my $rhs2 = shift;

	Alzabo::Exception::SQL->throw
	    ( error => "The BETWEEN comparison operator cannot accept a subselect" )

lib/Alzabo/SQLMaker.pm view on Meta::CPAN

	if( $rhs->isa('Alzabo::SQLMaker') )
	{
	    $self->{sql} .= '(';
	    $self->{sql} .= $self->_subselect($rhs);
	    $self->{sql} .= ')';
	}
	else
	{
	    $self->{sql} .= $self->_rhs($rhs);
	}
    }
}

sub _rhs
{
    my $self = shift;
    my $rhs = shift;

    if ( Alzabo::Utils::safe_can( $rhs, 'table' ) )
    {
	unless ( $self->{tables}{ $rhs->table } )
	{
	    my $err = 'Cannot use column (';
	    $err .= join '.', $rhs->table->name, $rhs->name;
	    $err .= ") in $self->{type} unless its table is included in the ";
	    $err .= $self->{type} eq 'update' ? 'UPDATE' : 'FROM';
	    $err .= ' clause';
	    Alzabo::Exception::SQL->throw( error => $err );
	}

	return ( $self->{quote_identifiers} ?
                 $self->{driver}->quote_identifier( $rhs->table->alias_name, $rhs->name ) :
                 $rhs->table->alias_name . '.' . $rhs->name );
    }
    else
    {
	return $self->_bind_val($rhs);
    }
}

sub _subselect
{
    my $self = shift;
    my $sql = shift;

    push @{ $self->{bind} }, @{ $sql->bind };

    return $sql->sql;
}

sub order_by
{
    my $self = shift;

    $self->_assert_last_op( qw( select from condition group_by ) );

    Alzabo::Exception::SQL->throw
	( error => "Cannot use order by in a '$self->{type}' statement" )
	    unless $self->{type} eq 'select';

    validate_pos( @_, ( { type => SCALAR | OBJECT,
			  callbacks =>
			  { 'column_or_function_or_sort' =>
			    sub { Alzabo::Utils::safe_can( $_[0], 'table' ) ||
				  Alzabo::Utils::safe_isa( $_[0], 'Alzabo::SQLMaker::Function' ) ||
				  $_[0] =~ /^(?:ASC|DESC)$/i } } }
		      ) x @_ );

    $self->{sql} .= ' ORDER BY ';

    my $x = 0;
    my $last = '';
    foreach my $i (@_)
    {
	if ( Alzabo::Utils::safe_can( $i, 'table' ) )
	{
	    unless ( $self->{tables}{ $i->table } )
	    {
		my $err = 'Cannot use column (';
		$err .= join '.', $i->table->name, $i->name;
		$err .= ") in $self->{type} unless its table is included in the FROM clause";
		Alzabo::Exception::SQL->throw( error => $err );
	    }

	    # no comma needed for first column
	    $self->{sql} .= ', ', if $x++;
	    $self->{sql} .=
		( $self->{quote_identifiers} ?
                  $self->{driver}->quote_identifier( $i->table->alias_name, $i->alias_name ) :
                  $i->table->alias_name . '.' . $i->alias_name );

	    $last = 'column';
	}
	elsif ( Alzabo::Utils::safe_isa( $i, 'Alzabo::SQLMaker::Function' ) )
	{
	    my $string = $i->as_string( $self->{driver}, $self->{quote_identifiers} );
	    if ( exists $self->{functions}{$string} )
	    {
		$self->{sql} .= ', ', if $x++;
		$self->{sql} .= $self->{functions}{$string};
	    }
	    else
	    {
		$self->{sql} .= ', ', if $x++;
		$self->{sql} .= $string;
	    }

            $last = 'function';
	}
	else
	{
	    Alzabo::Exception::Params->throw
		( error => 'A sort specifier cannot follow another sort specifier in an ORDER BY clause' )
		    if $last eq 'sort';

	    $self->{sql} .= " \U$i";

	    $last = 'sort';
	}
    }

    $self->{last_op} = 'order_by';

    return $self;
}

sub group_by
{
    my $self = shift;

    $self->_assert_last_op( qw( select from condition ) );

    Alzabo::Exception::SQL->throw
	( error => "Cannot use group by in a '$self->{type}' statement" )
	    unless $self->{type} eq 'select';

    validate_pos( @_, ( { can => 'table' } ) x @_ );

    foreach my $c (@_)
    {
	unless ( $self->{tables}{ $c->table } )
	{
	    my $err = 'Cannot use column (';
	    $err .= join '.', $c->table->name, $c->name;
	    $err .= ") in $self->{type} unless its table is included in the FROM clause";
	    Alzabo::Exception::SQL->throw( error => $err );
	}
    }

    $self->{sql} .= ' GROUP BY ';
    $self->{sql} .=
	( join ', ',
	  map { ( $self->{quote_identifiers} ?
                  $self->{driver}->quote_identifier( $_->table->alias_name, $_->alias_name ) :
                  $_->table->alias_name . '.' . $_->alias_name ) }
	  @_ );

    $self->{last_op} = 'group_by';

    return $self;
}

sub insert
{
    my $self = shift;

    $self->{sql} .= 'INSERT ';

    $self->{type} = 'insert';
    $self->{last_op} = 'insert';

    return $self;
}

sub into
{
    my $self = shift;

    $self->_assert_last_op( qw( insert ) );

    validate_pos( @_, { can => 'alias_name' }, ( { can => 'table' } ) x (@_ - 1) );

    my $table = shift;
    $self->{tables} = { $table => 1 };

    foreach my $c (@_)
    {
	unless ( $c->table eq $table )
	{
	    my $err = 'Cannot into column (';
	    $err .= join '.', $c->table->name, $c->name;
	    $err .= ') because its table was not the one specified in the INTO clause';
	    Alzabo::Exception::SQL->throw( error => $err );
	}
    }

    $self->{columns} = [ @_ ? @_ : $table->columns ];

    $self->{sql} .= 'INTO ';

    $self->{sql} .= ( $self->{quote_identifiers} ?
                      $self->{driver}->quote_identifier( $table->name ) :
                      $table->name );

    $self->{sql} .= ' (';

    $self->{sql} .=
	( join ', ',
	  map { ( $self->{quote_identifiers} ?
                  $self->{driver}->quote_identifier( $_->name ) :
                  $_->name ) }
	  @{ $self->{columns} } );

    $self->{sql} .= ') ';

    $self->{last_op} = 'into';

    return $self;
}

sub values
{
    my $self = shift;

    $self->_assert_last_op( qw( into ) );

    validate_pos( @_, ( { type => UNDEF | SCALAR | OBJECT } ) x @_ );

    if ( ref $_[0] && $_[0]->isa('Alzabo::SQLMaker') )
    {
	$self->{sql} = $_[0]->sql;
	push @{ $self->{bind} }, $_[0]->bind;
    }
    else
    {
	my @vals = @_;

	Alzabo::Exception::Params->throw
	    ( error => "'values' method expects key/value pairs of column objects and values'" )
		if !@vals || @vals % 2;

	my %vals = map { ref $_ && $_->can('table') ? $_->name : $_ } @vals;
	foreach my $c ( @vals[ map { $_ * 2 } 0 .. int($#vals/2) ] )
	{
	    Alzabo::Exception::SQL->throw
		( error => $c->name . " column was not specified in the into method call" )
		    unless grep { $c eq $_ } @{ $self->{columns} };
	}

	foreach my $c ( @{ $self->{columns } } )
	{
	    Alzabo::Exception::SQL->throw
		( error => $c->name . " was specified in the into method call but no value was provided" )
		    unless exists $vals{ $c->name };
	}

	$self->{sql} .= 'VALUES (';
	$self->{sql} .=
            join ', ', ( map { $self->_bind_val_for_insert( $_, $vals{ $_->name } ) }
                         @{ $self->{columns} }
                       );
	$self->{sql} .= ')';
    }

    if ( @{ $self->{placeholders} } && @{ $self->{bind} } )
    {
        Alzabo::Exception::SQL->throw
	    ( error => "Cannot mix actual bound values and placeholders in call to values()" );
    }

    $self->{last_op} = 'values';

    return $self;
}

use constant UPDATE_SPEC => { can => 'alias_name' };

sub update
{
    my $self = shift;

    validate_pos( @_, UPDATE_SPEC );

    my $table = shift;

    $self->{sql} = 'UPDATE ';

    $self->{sql} .= ( $self->{quote_identifiers} ?
                      $self->{driver}->quote_identifier( $table->name ) :
                      $table->name );

    $self->{tables} = { $table => 1 };

    $self->{type} = 'update';
    $self->{last_op} = 'update';

    return $self;
}

sub set
{
    my $self = shift;
    my @vals = @_;

    $self->_assert_last_op('update');

    Alzabo::Exception::Params->throw
	( error => "'set' method expects key/value pairs of column objects and values'" )
	    if !@vals || @vals % 2;

    validate_pos( @_, ( { can => 'table' },
			{ type => UNDEF | SCALAR | OBJECT } ) x (@vals / 2) );

    $self->{sql} .= ' SET ';

    my @set;
    my $table = ( keys %{ $self->{tables} } )[0];
    while ( my ($col, $val) = splice @vals, 0, 2 )
    {
	unless ( $table eq $col->table )
	{
	    my $err = 'Cannot set column (';
	    $err .= join '.', $col->table->name, $col->name;
	    $err .= ') unless its table is included in the UPDATE clause';
	    Alzabo::Exception::SQL->throw( error => $err );
	}

	push @set,
	    ( $self->{quote_identifiers} ?
              $self->{driver}->quote_identifier( $col->name ) :
              $col->name ) .
            ' = ' . $self->_bind_val($val);
    }
    $self->{sql} .= join ', ', @set;

    $self->{last_op} = 'set';

    return $self;
}

sub delete
{
    my $self = shift;

    $self->{sql} .= 'DELETE ';

    $self->{type} = 'delete';
    $self->{last_op} = 'delete';

    return $self;
}

sub _assert_last_op
{
    my $self = shift;

    unless ( grep { $self->{last_op} eq $_ } @_ )
    {
	my $op = (caller(1))[3];
	$op =~ s/.*::(.*?)$/$1/;
	Alzabo::Exception::SQL->throw( error => "Cannot follow $self->{last_op} with $op" );
    }
}

use constant _BIND_VAL_FOR_INSERT_SPEC => ( { isa => 'Alzabo::Runtime::Column' },
                                            { type => UNDEF | SCALAR | OBJECT }
                                          );


sub _bind_val_for_insert
{
    my $self = shift;

    my ( $col, $val ) =
        validate_pos( @_, _BIND_VAL_FOR_INSERT_SPEC );

    if ( defined $val && $val eq $placeholder )
    {
        push @{ $self->{placeholders} }, $col->name;
        return '?';
    }
    else
    {
        return $self->_bind_val($val);
    }
}

use constant _BIND_VAL_SPEC => { type => UNDEF | SCALAR | OBJECT };

sub _bind_val
{
    my $self = shift;

    validate_pos( @_, _BIND_VAL_SPEC );

    return $_[0]->as_string( $self->{driver}, $self->{quote_identifiers} )
        if Alzabo::Utils::safe_isa( $_[0], 'Alzabo::SQLMaker::Function' );

    push @{ $self->{bind} }, $_[0];
    return '?';
}

sub sql
{
    my $self = shift;

    Alzabo::Exception::SQL->throw( error => "SQL contains unbalanced parentheses subgrouping: $self->{sql}" )
	if $self->{subgroup};

    return $self->{sql};
}

sub bind
{
    my $self = shift;
    return $self->{bind};
}

sub placeholders
{
    my $self = shift;

    my $x = 0;

    return map { $_ => $x++ } @{ $self->{placeholders} };
}

sub limit
{
    shift()->_virtual;
}

sub get_limit
{
    shift()->_virtual;
}

sub sqlmaker_id
{
    shift()->_virtual;
}

sub distinct_requires_order_by_in_select { 0 }

sub _virtual
{
    my $self = shift;

    my $sub = (caller(1))[3];
    $sub =~ s/.*::(.*?)$/$1/;
    Alzabo::Exception::VirtualMethod->throw( error =>
					     "$sub is a virtual method and must be subclassed in " . ref $self );
}

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