|
0 |
package Class::DBI::Plugin::Pager;
|
|
1 |
use strict;
|
|
2 |
use warnings;
|
|
3 |
use Carp;
|
|
4 |
|
|
5 |
use UNIVERSAL::require;
|
|
6 |
use SQL::Abstract;
|
|
7 |
|
|
8 |
use base qw( Data::Page Class::Data::Inheritable );
|
|
9 |
|
|
10 |
use vars qw( $VERSION );
|
|
11 |
|
|
12 |
$VERSION = 0.561;
|
|
13 |
|
|
14 |
# D::P inherits from Class::Accessor::Chained::Fast
|
|
15 |
__PACKAGE__->mk_accessors( qw( where abstract_attr per_page page order_by _cdbi_app ) );
|
|
16 |
|
|
17 |
__PACKAGE__->mk_classdata( '_syntax' );
|
|
18 |
__PACKAGE__->mk_classdata( '_pager_class' );
|
|
19 |
|
|
20 |
|
|
21 |
=head1 NAME
|
|
22 |
|
|
23 |
Class::DBI::Plugin::Pager - paged queries for CDBI
|
|
24 |
|
|
25 |
=head1 DESCRIPTION
|
|
26 |
|
|
27 |
Adds a pager method to your class that can query using SQL::Abstract where clauses,
|
|
28 |
and limit the number of rows returned to a specific subset.
|
|
29 |
|
|
30 |
=head1 SYNOPSIS
|
|
31 |
|
|
32 |
package CD;
|
|
33 |
use base 'Class::DBI';
|
|
34 |
|
|
35 |
use Class::DBI::Plugin::AbstractCount; # pager needs this
|
|
36 |
use Class::DBI::Plugin::Pager;
|
|
37 |
|
|
38 |
# or to use a different syntax
|
|
39 |
# use Class::DBI::Plugin::Pager::RowsTo;
|
|
40 |
|
|
41 |
__PACKAGE__->set_db(...);
|
|
42 |
|
|
43 |
|
|
44 |
# in a nearby piece of code...
|
|
45 |
|
|
46 |
use CD;
|
|
47 |
|
|
48 |
# see SQL::Abstract for how to specify the query
|
|
49 |
my $where = { ... };
|
|
50 |
|
|
51 |
my $order_by => [ qw( foo bar ) ];
|
|
52 |
|
|
53 |
# bit by bit:
|
|
54 |
my $pager = CD->pager;
|
|
55 |
|
|
56 |
$pager->per_page( 10 );
|
|
57 |
$pager->page( 3 );
|
|
58 |
$pager->where( $where );
|
|
59 |
$pager->order_by( $order_by );
|
|
60 |
|
|
61 |
$pager->set_syntax( 'RowsTo' );
|
|
62 |
|
|
63 |
my @cds = $pager->search_where;
|
|
64 |
|
|
65 |
# or all at once
|
|
66 |
my $pager = CD->pager( $where, $order_by, 10, 3 );
|
|
67 |
|
|
68 |
my @cds = $pager->search_where;
|
|
69 |
|
|
70 |
# or
|
|
71 |
|
|
72 |
my $pager = CD->pager;
|
|
73 |
|
|
74 |
my @cds = $pager->search_where( $where, $order_by, 10, 3 );
|
|
75 |
|
|
76 |
# $pager isa Data::Page
|
|
77 |
# @cds contains the CDs just for the current page
|
|
78 |
|
|
79 |
=head1 METHODS
|
|
80 |
|
|
81 |
=over
|
|
82 |
|
|
83 |
=item import
|
|
84 |
|
|
85 |
Loads the C<pager> method into the CDBI app.
|
|
86 |
|
|
87 |
=cut
|
|
88 |
|
|
89 |
sub import {
|
|
90 |
my ( $class ) = @_; # the pager class or subclass
|
|
91 |
|
|
92 |
__PACKAGE__->_pager_class( $class );
|
|
93 |
|
|
94 |
my $caller;
|
|
95 |
|
|
96 |
# find the app - supports subclassing (My::Pager is_a CDBI::P::Pager, not_a CDBI)
|
|
97 |
foreach my $level ( 0 .. 10 )
|
|
98 |
{
|
|
99 |
$caller = caller( $level );
|
|
100 |
last if UNIVERSAL::isa( $caller, 'Class::DBI' )
|
|
101 |
}
|
|
102 |
|
|
103 |
warn( "can't find the CDBI app" ), return unless $caller;
|
|
104 |
#croak( "can't find the CDBI app" ) unless $caller;
|
|
105 |
|
|
106 |
no strict 'refs';
|
|
107 |
*{"$caller\::pager"} = \&pager;
|
|
108 |
}
|
|
109 |
|
|
110 |
=item pager( [$where, [$abstract_attr]], [$order_by], [$per_page], [$page], [$syntax] )
|
|
111 |
|
|
112 |
Also accepts named arguments:
|
|
113 |
|
|
114 |
where => $where,
|
|
115 |
abstract_attr => $attr,
|
|
116 |
order_by => $order_by,
|
|
117 |
per_page => $per_page,
|
|
118 |
page => $page,
|
|
119 |
syntax => $syntax
|
|
120 |
|
|
121 |
Returns a pager object. This subclasses L<Data::Page>.
|
|
122 |
|
|
123 |
Note that for positional arguments, C<$abstract_attr> can only be passed if
|
|
124 |
preceded by a C<$where> argument.
|
|
125 |
|
|
126 |
C<$abstract_attr> can contain the C<$order_by> setting (just as in
|
|
127 |
L<SQL::Abstract|SQL::Abstract>).
|
|
128 |
|
|
129 |
=over 4
|
|
130 |
|
|
131 |
=item configuration
|
|
132 |
|
|
133 |
The named arguments all exist as get/set methods.
|
|
134 |
|
|
135 |
=over 4
|
|
136 |
|
|
137 |
=item where
|
|
138 |
|
|
139 |
A hashref specifying the query. See L<SQL::Abstract|SQL::Abstract>.
|
|
140 |
|
|
141 |
=item abstract_attr
|
|
142 |
|
|
143 |
A hashref specifying extra options to be passed through to the
|
|
144 |
L<SQL::Abstract|SQL::Abstract> constructor.
|
|
145 |
|
|
146 |
=item order_by
|
|
147 |
|
|
148 |
Single column name or arrayref of column names for the ORDER BY clause.
|
|
149 |
Defaults to the primary key(s) if not set.
|
|
150 |
|
|
151 |
=item per_page
|
|
152 |
|
|
153 |
Number of results per page.
|
|
154 |
|
|
155 |
=item page
|
|
156 |
|
|
157 |
The pager will retrieve results just for this page. Defaults to 1.
|
|
158 |
|
|
159 |
=item syntax
|
|
160 |
|
|
161 |
Change the way the 'limit' clause is constructed. See C<set_syntax>. Default
|
|
162 |
is C<LimitOffset>.
|
|
163 |
|
|
164 |
=back
|
|
165 |
|
|
166 |
=back
|
|
167 |
|
|
168 |
=cut
|
|
169 |
|
|
170 |
sub pager {
|
|
171 |
my $cdbi = shift;
|
|
172 |
|
|
173 |
my $class = __PACKAGE__->_pager_class;
|
|
174 |
|
|
175 |
my $self = bless {}, $class;
|
|
176 |
|
|
177 |
$self->_cdbi_app( $cdbi );
|
|
178 |
|
|
179 |
# This has to come before _init, so the caller can choose to set the syntax
|
|
180 |
# instead. But don't auto-set if we're a subclass.
|
|
181 |
$self->auto_set_syntax if $class eq __PACKAGE__;
|
|
182 |
|
|
183 |
$self->_init( @_ );
|
|
184 |
|
|
185 |
return $self;
|
|
186 |
}
|
|
187 |
|
|
188 |
# _init is also called by results, so preserve any existing settings if
|
|
189 |
# new settings are not provided
|
|
190 |
sub _init {
|
|
191 |
my $self = shift;
|
|
192 |
|
|
193 |
return unless @_;
|
|
194 |
|
|
195 |
my ( $where, $abstract_attr, $order_by, $per_page, $page, $syntax );
|
|
196 |
|
|
197 |
if ( ref( $_[0] ) or $_[0] =~ /^\d+$/ )
|
|
198 |
{
|
|
199 |
$where = shift if ref $_[0]; # SQL::Abstract accepts a hashref or an arrayref
|
|
200 |
$abstract_attr = shift if ref $_[0] eq 'HASH';
|
|
201 |
# $order_by = shift unless $_[0] =~ /^\d+$/;
|
|
202 |
# $per_page = shift if $_[0] =~ /^\d+$/;
|
|
203 |
# $page = shift if $_[0] =~ /^\d+$/;
|
|
204 |
$order_by = shift unless $_[0] and $_[0] =~ /^\d+$/;
|
|
205 |
$per_page = shift if $_[0] and $_[0] =~ /^\d+$/;
|
|
206 |
$page = shift if $_[0] and $_[0] =~ /^\d+$/;
|
|
207 |
$syntax = shift;
|
|
208 |
}
|
|
209 |
else
|
|
210 |
{
|
|
211 |
my %args = @_;
|
|
212 |
|
|
213 |
$where = $args{where};
|
|
214 |
$abstract_attr = $args{abstract_attr};
|
|
215 |
$order_by = $args{order_by};
|
|
216 |
$per_page = $args{per_page};
|
|
217 |
$page = $args{page};
|
|
218 |
$syntax = $args{syntax};
|
|
219 |
}
|
|
220 |
|
|
221 |
# Emulate AbstractSearch's search_where ordering -VV 20041209
|
|
222 |
$order_by = delete $$abstract_attr{order_by} if ($abstract_attr and !$order_by);
|
|
223 |
|
|
224 |
$self->per_page( $per_page ) if $per_page;
|
|
225 |
$self->set_syntax( $syntax ) if $syntax;
|
|
226 |
$self->abstract_attr( $abstract_attr )if $abstract_attr;
|
|
227 |
$self->where( $where ) if $where;
|
|
228 |
$self->order_by( $order_by ) if $order_by;
|
|
229 |
$self->page( $page ) if $page;
|
|
230 |
}
|
|
231 |
|
|
232 |
=item search_where
|
|
233 |
|
|
234 |
Retrieves results from the pager. Accepts the same arguments as the C<pager>
|
|
235 |
method.
|
|
236 |
|
|
237 |
=cut
|
|
238 |
|
|
239 |
# like CDBI::AbstractSearch::search_where, with extra limitations
|
|
240 |
sub search_where {
|
|
241 |
my $self = shift;
|
|
242 |
|
|
243 |
$self->_init( @_ );
|
|
244 |
|
|
245 |
$self->_setup_pager;
|
|
246 |
|
|
247 |
my $cdbi = $self->_cdbi_app;
|
|
248 |
|
|
249 |
my $order_by = $self->order_by || [ $cdbi->primary_columns ];
|
|
250 |
my $where = $self->where;
|
|
251 |
my $syntax = $self->_syntax || $self->set_syntax;
|
|
252 |
my $limit_phrase = $self->$syntax;
|
|
253 |
my $sql = SQL::Abstract->new( %{ $self->abstract_attr || {} } );
|
|
254 |
|
|
255 |
$order_by = [ $order_by ] unless ref $order_by;
|
|
256 |
my ( $phrase, @bind ) = $sql->where( $where, $order_by );
|
|
257 |
|
|
258 |
# If the phrase starts with the ORDER clause (i.e. no WHERE spec), then we are
|
|
259 |
# emulating a { 1 => 1 } search, but avoiding the bug in Class::DBI::Plugin::AbstractCount 0.04,
|
|
260 |
# so we need to replace the spec - patch from Will Hawes
|
|
261 |
if ( $phrase =~ /^\s*ORDER\s*/i )
|
|
262 |
{
|
|
263 |
$phrase = ' 1=1' . $phrase;
|
|
264 |
}
|
|
265 |
|
|
266 |
|
|
267 |
$phrase .= ' ' . $limit_phrase;
|
|
268 |
$phrase =~ s/^\s*WHERE\s*//i;
|
|
269 |
|
|
270 |
return $cdbi->retrieve_from_sql( $phrase, @bind );
|
|
271 |
}
|
|
272 |
|
|
273 |
=item retrieve_all
|
|
274 |
|
|
275 |
Convenience method, generates a WHERE clause that matches all rows from the table.
|
|
276 |
|
|
277 |
Accepts the same arguments as the C<pager> or C<search_where> methods, except that no
|
|
278 |
WHERE clause should be specified.
|
|
279 |
|
|
280 |
Note that the argument parsing routine called by the C<pager> method cannot cope with
|
|
281 |
positional arguments that lack a WHERE clause, so either use named arguments, or the
|
|
282 |
'bit by bit' approach, or pass the arguments directly to C<retrieve_all>.
|
|
283 |
|
|
284 |
=cut
|
|
285 |
|
|
286 |
sub retrieve_all
|
|
287 |
{
|
|
288 |
my $self = shift;
|
|
289 |
|
|
290 |
my $get_all = {}; # { 1 => 1 };
|
|
291 |
|
|
292 |
unless ( @_ )
|
|
293 |
{ # already set pager up via method calls
|
|
294 |
$self->where( $get_all );
|
|
295 |
return $self->search_where;
|
|
296 |
}
|
|
297 |
|
|
298 |
my @args = ( ref( $_[0] ) or $_[0] =~ /^\d+$/ ) ?
|
|
299 |
( $get_all, @_ ) : # send an array
|
|
300 |
( where => $get_all, @_ ); # send a hash
|
|
301 |
|
|
302 |
return $self->search_where( @args );
|
|
303 |
}
|
|
304 |
|
|
305 |
sub _setup_pager
|
|
306 |
{
|
|
307 |
my ( $self ) = @_;
|
|
308 |
|
|
309 |
my $where = $self->where || {};
|
|
310 |
|
|
311 |
# fix { 1 => 1 } as a special case - Class::DBI::Plugin::AbstractCount 0.04 has a bug in
|
|
312 |
# its column-checking code
|
|
313 |
if ( ref( $where ) eq 'HASH' and $where->{1} )
|
|
314 |
{
|
|
315 |
$where = {};
|
|
316 |
$self->where( {} );
|
|
317 |
}
|
|
318 |
|
|
319 |
my $per_page = $self->per_page || croak( 'no. of entries per page not specified' );
|
|
320 |
my $cdbi = $self->_cdbi_app;
|
|
321 |
my $count = $cdbi->count_search_where( $where, $self->abstract_attr );
|
|
322 |
my $page = $self->page || 1;
|
|
323 |
|
|
324 |
$self->total_entries( $count );
|
|
325 |
$self->entries_per_page( $per_page );
|
|
326 |
$self->current_page( $page );
|
|
327 |
|
|
328 |
croak( 'Fewer than one entry per page!' ) if $self->entries_per_page < 1;
|
|
329 |
|
|
330 |
$self->current_page( $self->first_page ) unless defined $self->current_page;
|
|
331 |
$self->current_page( $self->first_page ) if $self->current_page < $self->first_page;
|
|
332 |
$self->current_page( $self->last_page ) if $self->current_page > $self->last_page;
|
|
333 |
}
|
|
334 |
|
|
335 |
# SQL::Abstract::_recurse_where eats the WHERE clause
|
|
336 |
#sub where {
|
|
337 |
# my ( $self, $where_ref ) = @_;
|
|
338 |
#
|
|
339 |
# return $self->_where unless $where_ref;
|
|
340 |
#
|
|
341 |
# my $where_copy;
|
|
342 |
#
|
|
343 |
# if ( ref( $where_ref ) eq 'HASH' ) {
|
|
344 |
# $where_copy = { %$where_ref };
|
|
345 |
# }
|
|
346 |
# elsif ( ref( $where_ref ) eq 'ARRAY' )
|
|
347 |
# {
|
|
348 |
# $where_copy = [ @$where_ref ];
|
|
349 |
# }
|
|
350 |
# else
|
|
351 |
# {
|
|
352 |
# die "WHERE clause [$where_ref] must be specified as an ARRAYREF or HASHREF";
|
|
353 |
# }
|
|
354 |
#
|
|
355 |
# # this will get eaten, but the caller's value is now protected
|
|
356 |
# $self->_where( $where_copy );
|
|
357 |
#}
|
|
358 |
|
|
359 |
=item set_syntax( [ $name || $class || $coderef ] )
|
|
360 |
|
|
361 |
Changes the syntax used to generate the C<limit> or other phrase that restricts
|
|
362 |
the results set to the required page.
|
|
363 |
|
|
364 |
The syntax is implemented as a method called on the pager, which can be
|
|
365 |
queried to provide the C<$rows> and C<$offset> parameters (see the subclasses
|
|
366 |
included in this distribution).
|
|
367 |
|
|
368 |
=over 4
|
|
369 |
|
|
370 |
=item $class
|
|
371 |
|
|
372 |
A class with a C<make_limit> method.
|
|
373 |
|
|
374 |
=item $name
|
|
375 |
|
|
376 |
Name of a class in the C<Class::DBI::Plugin::Pager::> namespace, which has a
|
|
377 |
C<make_limit> method.
|
|
378 |
|
|
379 |
=item $coderef
|
|
380 |
|
|
381 |
Will be called as a method on the pager object, so receives the pager as its
|
|
382 |
argument.
|
|
383 |
|
|
384 |
=item (no args)
|
|
385 |
|
|
386 |
Called without args, will default to C<LimitOffset>, which causes
|
|
387 |
L<Class::DBI::Plugin::Pager::LimitOffset|Class::DBI::Plugin::Pager::LimitOffset>
|
|
388 |
to be used.
|
|
389 |
|
|
390 |
=back
|
|
391 |
|
|
392 |
=cut
|
|
393 |
|
|
394 |
sub set_syntax {
|
|
395 |
my ( $proto, $syntax ) = @_;
|
|
396 |
|
|
397 |
# pick up default from subclass, or load from LimitOffset
|
|
398 |
$syntax ||= $proto->can( 'make_limit' );
|
|
399 |
$syntax ||= 'LimitOffset';
|
|
400 |
|
|
401 |
if ( ref( $syntax ) eq 'CODE' )
|
|
402 |
{
|
|
403 |
$proto->_syntax( $syntax );
|
|
404 |
return $syntax;
|
|
405 |
}
|
|
406 |
|
|
407 |
my $format_class = $syntax =~ '::' ? $syntax : "Class::DBI::Plugin::Pager::$syntax";
|
|
408 |
|
|
409 |
$format_class->require || croak "error loading $format_class: $UNIVERSAL::require::ERROR";
|
|
410 |
|
|
411 |
my $formatter = $format_class->can( 'make_limit' ) || croak "no make_limit method in $format_class";
|
|
412 |
|
|
413 |
$proto->_syntax( $formatter );
|
|
414 |
|
|
415 |
return $formatter;
|
|
416 |
}
|
|
417 |
|
|
418 |
=item auto_set_syntax
|
|
419 |
|
|
420 |
This is called automatically when you call C<pager>, and attempts to set the
|
|
421 |
syntax automatically.
|
|
422 |
|
|
423 |
If you are using a subclass of the pager, this method will not be called.
|
|
424 |
|
|
425 |
Will C<die> if using Oracle or DB2, since there is no simple syntax for limiting
|
|
426 |
the results set. DB2 has a C<FETCH> keyword, but that seems to apply to a
|
|
427 |
cursor and I don't know if there is a cursor available to the pager. There
|
|
428 |
should probably be others to add to the unsupported list.
|
|
429 |
|
|
430 |
Supports the following drivers:
|
|
431 |
|
|
432 |
DRIVER CDBI::P::Pager subclass
|
|
433 |
my %supported = ( pg => 'LimitOffset',
|
|
434 |
mysql => 'LimitOffset', # older versions need LimitXY
|
|
435 |
sqlite => 'LimitOffset', # or LimitYX
|
|
436 |
sqlite2 => 'LimitOffset', # or LimitYX
|
|
437 |
interbase => 'RowsTo',
|
|
438 |
firebird => 'RowsTo',
|
|
439 |
);
|
|
440 |
|
|
441 |
Older versions of MySQL should use the LimitXY syntax. You'll need to set it
|
|
442 |
manually, either by C<use CDBI::P::Pager::LimitXY>, or by passing
|
|
443 |
C<syntax =E<gt> 'LimitXY'> to a method call, or call C<set_syntax> directly.
|
|
444 |
|
|
445 |
Any driver not in the supported or unsupported lists defaults to LimitOffset.
|
|
446 |
|
|
447 |
Any additions to the supported and unsupported lists gratefully received.
|
|
448 |
|
|
449 |
=cut
|
|
450 |
|
|
451 |
sub auto_set_syntax {
|
|
452 |
my ( $self ) = @_;
|
|
453 |
|
|
454 |
# not an exhaustive list
|
|
455 |
my %not_supported = ( oracle => 'Oracle',
|
|
456 |
db2 => 'DB2',
|
|
457 |
);
|
|
458 |
|
|
459 |
# additions welcome
|
|
460 |
my %supported = ( pg => 'LimitOffset',
|
|
461 |
mysql => 'LimitOffset', # older versions need LimitXY
|
|
462 |
sqlite => 'LimitOffset', # or LimitYX
|
|
463 |
sqlite2 => 'LimitOffset', # or LimitYX
|
|
464 |
interbase => 'RowsTo',
|
|
465 |
firebird => 'RowsTo',
|
|
466 |
);
|
|
467 |
|
|
468 |
my $cdbi = $self->_cdbi_app;
|
|
469 |
|
|
470 |
my $driver = lc( $cdbi->__driver );
|
|
471 |
|
|
472 |
die __PACKAGE__ . " can't build limit clauses for $not_supported{ $driver }"
|
|
473 |
if $not_supported{ $driver };
|
|
474 |
|
|
475 |
#warn sprintf "Setting syntax to %s for $driver", $supported{ $driver } || 'LimitOffset';
|
|
476 |
|
|
477 |
$self->set_syntax( $supported{ $driver } || 'LimitOffset' );
|
|
478 |
}
|
|
479 |
|
|
480 |
1;
|
|
481 |
|
|
482 |
__END__
|
|
483 |
|
|
484 |
#=for notes
|
|
485 |
#
|
|
486 |
#Would this work?
|
|
487 |
#
|
|
488 |
#with $limit and $offset defined.
|
|
489 |
#
|
|
490 |
#my $last = $limit + $offset
|
|
491 |
#
|
|
492 |
#my $order_by_str = join( ', ', @$order_by )
|
|
493 |
#
|
|
494 |
#$cdbi->set_sql( emulate_limit => <<'');
|
|
495 |
# SELECT * FROM (
|
|
496 |
# SELECT TOP $limit * FROM (
|
|
497 |
# SELECT TOP $last __ESSENTIAL__
|
|
498 |
# FROM __TABLE__
|
|
499 |
# ORDER BY $order_by_str ASC
|
|
500 |
# ) AS foo ORDER BY $order_by_str DESC
|
|
501 |
# ) AS bar ORDER BY $order_by_str ASC
|
|
502 |
#
|
|
503 |
#
|
|
504 |
#e.g. MS Access (thanks Emanuele Zeppieri)
|
|
505 |
#
|
|
506 |
#to add LIMIT/OFFSET to this query:
|
|
507 |
#
|
|
508 |
#SELECT my_column
|
|
509 |
#FROM my_table
|
|
510 |
#ORDER BY my_column ASC
|
|
511 |
#
|
|
512 |
#say with the values LIMIT=5 OFFSET=10, you have to resort to the TOP
|
|
513 |
#clause and re-write it this way:
|
|
514 |
#
|
|
515 |
#SELECT * FROM (
|
|
516 |
# SELECT TOP 5 * FROM (
|
|
517 |
# SELECT TOP 15 my_column
|
|
518 |
# FROM my_table
|
|
519 |
# ORDER BY my_column ASC
|
|
520 |
# ) AS foo ORDER BY my_column DESC
|
|
521 |
#) AS bar ORDER BY my_column ASC
|
|
522 |
#
|
|
523 |
#=cut
|
|
524 |
|
|
525 |
=back
|
|
526 |
|
|
527 |
=head2 SUBCLASSING
|
|
528 |
|
|
529 |
The 'limit' syntax can be set by using a subclass, e.g.
|
|
530 |
|
|
531 |
use Class::DBI::Plugin::Pager::RowsTo;
|
|
532 |
|
|
533 |
instead of setting at runtime. A subclass looks like this:
|
|
534 |
|
|
535 |
package Class::DBI::Plugin::Pager::RowsTo;
|
|
536 |
use base 'Class::DBI::Plugin::Pager';
|
|
537 |
|
|
538 |
sub make_limit {
|
|
539 |
my ( $self ) = @_;
|
|
540 |
|
|
541 |
my $offset = $self->skipped;
|
|
542 |
my $rows = $self->entries_per_page;
|
|
543 |
|
|
544 |
my $last = $rows + $offset;
|
|
545 |
|
|
546 |
return "ROWS $offset TO $last";
|
|
547 |
}
|
|
548 |
|
|
549 |
1;
|
|
550 |
|
|
551 |
You can omit the C<use base> and switch syntax by calling
|
|
552 |
C<$pager-E<gt>set_syntax( 'RowsTo' )>. Or you can leave in the C<use base> and
|
|
553 |
still say C<$pager-E<gt>set_syntax( 'RowsTo' )>, because in this case the class is
|
|
554 |
C<require>d and the C<import> in the base class doesn't get called. Or something.
|
|
555 |
At any rate, It Works.
|
|
556 |
|
|
557 |
The subclasses implement the following LIMIT syntaxes:
|
|
558 |
|
|
559 |
=over
|
|
560 |
|
|
561 |
=item Class::DBI::Plugin::Pager::LimitOffset
|
|
562 |
|
|
563 |
LIMIT $rows OFFSET $offset
|
|
564 |
|
|
565 |
This is the default if your driver is not in the list of known drivers.
|
|
566 |
|
|
567 |
This should work for PostgreSQL, more recent MySQL, SQLite, and maybe some
|
|
568 |
others.
|
|
569 |
|
|
570 |
=item Class::DBI::Plugin::LimitXY
|
|
571 |
|
|
572 |
LIMIT $offset, $rows
|
|
573 |
|
|
574 |
Older versions of MySQL.
|
|
575 |
|
|
576 |
=item Class::DBI::Plugin::LimitYX
|
|
577 |
|
|
578 |
LIMIT $rows, $offset
|
|
579 |
|
|
580 |
SQLite.
|
|
581 |
|
|
582 |
=item Class::DBI::Plugin::RowsTo
|
|
583 |
|
|
584 |
ROWS $offset TO $offset + $rows
|
|
585 |
|
|
586 |
InterBase, also FireBird, maybe others?
|
|
587 |
|
|
588 |
=back
|
|
589 |
|
|
590 |
=head1 TODO
|
|
591 |
|
|
592 |
I've only used this on an older version of MySQL. Reports of this thing
|
|
593 |
working (or not) elsewhere would be useful.
|
|
594 |
|
|
595 |
It should be possible to use C<set_sql> to build the complex queries
|
|
596 |
required by some databases to emulate LIMIT (see notes in source).
|
|
597 |
|
|
598 |
=head1 CAVEATS
|
|
599 |
|
|
600 |
This class can't implement the subselect mechanism required by some databases
|
|
601 |
to emulate the LIMIT phrase, because it only has access to the WHERE clause,
|
|
602 |
not the whole SQL statement. At the moment.
|
|
603 |
|
|
604 |
Each query issues two requests to the database - the first to count the entire
|
|
605 |
result set, the second to retrieve the required subset of results. If your
|
|
606 |
tables are small it may be quicker to use L<Class::DBI::Pager|Class::DBI::Pager>.
|
|
607 |
|
|
608 |
The C<order_by> clause means the database has to retrieve (internally) and sort
|
|
609 |
the entire results set, before chopping out the requested subset. It's probably
|
|
610 |
a good idea to have an index on the column(s) used to order the results. For
|
|
611 |
huge tables, this approach to paging may be too inefficient.
|
|
612 |
|
|
613 |
=head1 DEPENDENCIES
|
|
614 |
|
|
615 |
L<SQL::Abstract|SQL::Abstract>,
|
|
616 |
L<Data::Page|Data::Page>,
|
|
617 |
L<Class::DBI::Plugin::AbstractCount|Class::DBI::Plugin::AbstractCount>,
|
|
618 |
L<Class::Accessor|Class::Accessor>,
|
|
619 |
L<Class::Data::Inheritable|Class::Data::Inheritable>,
|
|
620 |
L<Carp|Carp>.
|
|
621 |
|
|
622 |
=head1 SEE ALSO
|
|
623 |
|
|
624 |
L<Class::DBI::Pager|Class::DBI::Pager> does a similar job, but retrieves
|
|
625 |
the entire results set into memory before chopping out the page you want.
|
|
626 |
|
|
627 |
=head1 BUGS
|
|
628 |
|
|
629 |
Please report all bugs via the CPAN Request Tracker at
|
|
630 |
L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Class-DBI-Plugin-Pager>.
|
|
631 |
|
|
632 |
=head1 COPYRIGHT AND LICENSE
|
|
633 |
|
|
634 |
Copyright 2004 by David Baird.
|
|
635 |
|
|
636 |
This library is free software; you can redistribute it and/or modify
|
|
637 |
it under the same terms as Perl itself.
|
|
638 |
|
|
639 |
=head1 AUTHOR
|
|
640 |
|
|
641 |
David Baird, C<cpan@riverside-cms.co.uk>
|
|
642 |
|