1 package Data::Query::Renderer::SQL::Slice::FetchFirst;
3 use List::Util qw(reduce);
4 use Data::Query::ExprHelpers;
7 sub _render_slice_limit {
10 ($dq->{from} ? $self->_render($dq->{from}) : ()),
11 $self->_format_keyword('FETCH FIRST'),
12 sprintf("%i", $dq->{limit}{value}),
13 $self->_format_keyword('ROWS ONLY')
17 sub _slice_type { 'FetchFirst' }
21 unless ($dq->{offset}) {
22 return $self->_render_slice_limit($dq);
24 unless ($dq->{order_is_stable}) {
25 die $self->_slice_type." limit style requires a stable order";
27 die "Slice's inner is not a Select"
28 unless is_Select my $orig_select = $dq->{from};
31 my (@inside_select_list, @outside_select_list);
32 my $default_inside_alias;
33 SELECT: foreach my $s (@{$orig_select->{select}}) {
40 if (is_Identifier $s) {
41 if (!$name and @{$s->{elements}} == 2) {
42 $default_inside_alias ||= $s->{elements}[0];
43 if ($s->{elements}[0] eq $default_inside_alias) {
44 $alias_map{join('.',@{$s->{elements}})} = $s;
45 push @inside_select_list, $s;
46 push @outside_select_list, $s;
50 $name ||= join('__', @{$s->{elements}});
51 $key = join('.', @{$s->{elements}});
53 die "XXX not implemented yet" unless $name;
56 $name ||= sprintf("GENSYM__%03i",++$gensym_count);
57 push @inside_select_list, Alias($name, $s);
58 push @outside_select_list, $alias_map{$key} = Identifier($name);
60 my $order = $orig_select->{from};
61 my $order_gensym_count;
62 die "Slice's Select not followed by Order but order_is_stable set"
63 unless is_Order $order;
64 my (@order_nodes, %order_map);
65 while (is_Order $order) {
66 my $by = $order->{by};
67 if (is_Identifier $by) {
68 $default_inside_alias ||= $by->{elements}[0]
69 if @{$by->{elements}} == 2;
71 = $alias_map{join('.', @{$by->{elements}})}
74 @{$by->{elements}} == 2
75 and $by->{elements}[0] eq $default_inside_alias
79 my $name = sprintf("ORDER__BY__%03i",++$order_gensym_count);
80 push @inside_select_list, Alias($name, $by);
85 die "XXX not implemented yet";
87 push @order_nodes, $order;
88 $order = $order->{from};
90 my $inside_order = reduce {
91 Order($b->{by}, $b->{reverse}, $a)
92 } $order, reverse @order_nodes;
93 my $inside_select = Select(\@inside_select_list, $inside_order);
94 my $limit_plus_offset = +{
95 %{$dq->{limit}}, value => $dq->{limit}{value} + $dq->{offset}{value}
97 $default_inside_alias ||= 'me';
98 my $bridge_from = Alias(
99 $default_inside_alias,
100 Slice(undef, $limit_plus_offset, $inside_select)
102 my $outside_order = reduce {
103 Order($order_map{$b->{by}}, !$b->{reverse}, $a)
104 } $bridge_from, reverse @order_nodes;
105 my $outside_select = Select(
107 $dq->{preserve_order}
109 @outside_select_list,
110 grep @{$_->{elements}} == 1, @order_map{map $_->{by}, @order_nodes}
112 : \@outside_select_list,
116 my $final = Slice(undef, $dq->{limit}, $outside_select);
117 if ($dq->{preserve_order}) {
119 \@outside_select_list,
121 Order($order_map{$b->{by}}, $b->{reverse}, $a)
122 } Alias($default_inside_alias, $final), reverse @order_nodes
125 return $self->_render($final);