summaryrefslogtreecommitdiffstats
path: root/Bugzilla/Object.pm
blob: 456888b381aa16bedd54d88bf39d19113e4566e4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
# -*- Mode: perl; indent-tabs-mode: nil -*-
#
# The contents of this file are subject to the Mozilla Public
# License Version 1.1 (the "License"); you may not use this file
# except in compliance with the License. You may obtain a copy of
# the License at http://www.mozilla.org/MPL/
#
# Software distributed under the License is distributed on an "AS
# IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
# implied. See the License for the specific language governing
# rights and limitations under the License.
#
# The Original Code is the Bugzilla Bug Tracking System.
#
# The Initial Developer of the Original Code is Everything Solved.
# Portions created by Everything Solved are Copyright (C) 2006 
# Everything Solved. All Rights Reserved.
#
# Contributor(s): Max Kanat-Alexander <mkanat@bugzilla.org>
#                 Frédéric Buclin <LpSolit@gmail.com>

use strict;

package Bugzilla::Object;

use Bugzilla::Constants;
use Bugzilla::Util;
use Bugzilla::Error;

use Date::Parse;

use constant NAME_FIELD => 'name';
use constant ID_FIELD   => 'id';
use constant LIST_ORDER => NAME_FIELD;

use constant UPDATE_VALIDATORS => {};
use constant NUMERIC_COLUMNS   => ();
use constant DATE_COLUMNS      => ();

###############################
####    Initialization     ####
###############################

sub new {
    my $invocant = shift;
    my $class    = ref($invocant) || $invocant;
    my $object   = $class->_init(@_);
    bless($object, $class) if $object;
    return $object;
}


# Note: Because this uses sql_istrcmp, if you make a new object use
# Bugzilla::Object, make sure that you modify bz_setup_database
# in Bugzilla::DB::Pg appropriately, to add the right LOWER
# index. You can see examples already there.
sub _init {
    my $class = shift;
    my ($param) = @_;
    my $dbh = Bugzilla->dbh;
    my $columns = join(',', $class->DB_COLUMNS);
    my $table   = $class->DB_TABLE;
    my $name_field = $class->NAME_FIELD;
    my $id_field   = $class->ID_FIELD;

    my $id = $param;
    if (ref $param eq 'HASH') {
        $id = $param->{id};
    }
    my $object;

    if (defined $id) {
        # We special-case if somebody specifies an ID, so that we can
        # validate it as numeric.
        detaint_natural($id)
          || ThrowCodeError('param_must_be_numeric',
                            {function => $class . '::_init'});

        $object = $dbh->selectrow_hashref(qq{
            SELECT $columns FROM $table
             WHERE $id_field = ?}, undef, $id);
    } else {
        unless (defined $param->{name} || (defined $param->{'condition'} 
                                           && defined $param->{'values'}))
        {
            ThrowCodeError('bad_arg', { argument => 'param',
                                        function => $class . '::new' });
        }

        my ($condition, @values);
        if (defined $param->{name}) {
            $condition = $dbh->sql_istrcmp($name_field, '?');
            push(@values, $param->{name});
        }
        elsif (defined $param->{'condition'} && defined $param->{'values'}) {
            caller->isa('Bugzilla::Object')
                || ThrowCodeError('protection_violation',
                       { caller    => caller, 
                         function  => $class . '::new',
                         argument  => 'condition/values' });
            $condition = $param->{'condition'};
            push(@values, @{$param->{'values'}});
        }

        map { trick_taint($_) } @values;
        $object = $dbh->selectrow_hashref(
            "SELECT $columns FROM $table WHERE $condition", undef, @values);
    }

    return $object;
}

sub check {
    my ($invocant, $param) = @_;
    my $class = ref($invocant) || $invocant;
    # If we were just passed a name, then just use the name.
    if (!ref $param) {
        $param = { name => $param };
    }
    # Don't allow empty names or ids.
    my $check_param = exists $param->{id} ? $param->{id} : $param->{name};
    $check_param = trim($check_param);
    $check_param || ThrowUserError('object_not_specified', { class => $class });
    my $obj = $class->new($param);
    if (!$obj) {
        # We don't want to override the normal template "user" object if
        # "user" is one of the params.
        delete $param->{user};
        ThrowUserError('object_does_not_exist', { %$param, class => $class });
    }
    return $obj;
}

sub new_from_list {
    my $invocant = shift;
    my $class = ref($invocant) || $invocant;
    my ($id_list) = @_;
    my $id_field = $class->ID_FIELD;

    my @detainted_ids;
    foreach my $id (@$id_list) {
        detaint_natural($id) ||
            ThrowCodeError('param_must_be_numeric',
                          {function => $class . '::new_from_list'});
        push(@detainted_ids, $id);
    }
    # We don't do $invocant->match because some classes have
    # their own implementation of match which is not compatible
    # with this one. However, match() still needs to have the right $invocant
    # in order to do $class->DB_TABLE and so on.
    return match($invocant, { $id_field => \@detainted_ids });
}

# Note: Future extensions to this could be:
#  * Add a MATCH_JOIN constant so that we can join against
#    certain other tables for the WHERE criteria.
sub match {
    my ($invocant, $criteria) = @_;
    my $class = ref($invocant) || $invocant;
    my $dbh   = Bugzilla->dbh;

    return [$class->get_all] if !$criteria;

    my (@terms, @values, $postamble);
    foreach my $field (keys %$criteria) {
        my $value = $criteria->{$field};
        
        # allow for LIMIT and OFFSET expressions via the criteria.
        next if $field eq 'OFFSET';
        if ( $field eq 'LIMIT' ) {
            next unless defined $value;
            detaint_natural($value)
              or ThrowCodeError('param_must_be_numeric', 
                                { param    => 'LIMIT', 
                                  function => "${class}::match" });
            my $offset;
            if (defined $criteria->{OFFSET}) {
                $offset = $criteria->{OFFSET};
                detaint_signed($offset)
                  or ThrowCodeError('param_must_be_numeric', 
                                    { param    => 'OFFSET',
                                      function => "${class}::match" });
            }
            $postamble = $dbh->sql_limit($value, $offset);
            next;
        }
        elsif ( $field eq 'WHERE' ) {
            # the WHERE value is a hashref where the keys are
            # "column_name operator ?" and values are the placeholder's
            # value (either a scalar or an array of values).
            foreach my $k (keys %$value) {
                push(@terms, $k);
                my @this_value = ref($value->{$k}) ? @{ $value->{$k} } 
                                                   : ($value->{$k});
                push(@values, @this_value);
            }            
            next;
        }
        
        $class->_check_field($field, 'match');

        if (ref $value eq 'ARRAY') {
            # IN () is invalid SQL, and if we have an empty list
            # to match against, we're just returning an empty
            # array anyhow.
            return [] if !scalar @$value;

            my @qmarks = ("?") x @$value;
            push(@terms, $dbh->sql_in($field, \@qmarks));
            push(@values, @$value);
        }
        elsif ($value eq NOT_NULL) {
            push(@terms, "$field IS NOT NULL");
        }
        elsif ($value eq IS_NULL) {
            push(@terms, "$field IS NULL");
        }
        else {
            push(@terms, "$field = ?");
            push(@values, $value);
        }
    }

    my $where = join(' AND ', @terms) if scalar @terms;
    return $class->_do_list_select($where, \@values, $postamble);
}

sub _do_list_select {
    my ($class, $where, $values, $postamble) = @_;
    my $table = $class->DB_TABLE;
    my $cols  = join(',', $class->DB_COLUMNS);
    my $order = $class->LIST_ORDER;

    my $sql = "SELECT $cols FROM $table";
    if (defined $where) {
        $sql .= " WHERE $where ";
    }
    $sql .= " ORDER BY $order";
    
    $sql .= " $postamble" if $postamble;
        
    my $dbh = Bugzilla->dbh;
    # Sometimes the values are tainted, but we don't want to untaint them
    # for the caller. So we copy the array. It's safe to untaint because
    # they're only used in placeholders here.
    my @untainted = @{ $values || [] };
    trick_taint($_) foreach @untainted;
    my $objects = $dbh->selectall_arrayref($sql, {Slice=>{}}, @untainted);
    bless ($_, $class) foreach @$objects;
    return $objects
}

###############################
####      Accessors      ######
###############################

sub id   { return $_[0]->{$_[0]->ID_FIELD};   }
sub name { return $_[0]->{$_[0]->NAME_FIELD}; }

###############################
####        Methods        ####
###############################

sub set {
    my ($self, $field, $value) = @_;

    # This method is protected. It's used to help implement set_ functions.
    caller->isa('Bugzilla::Object')
        || ThrowCodeError('protection_violation', 
                          { caller     => caller,
                            superclass => __PACKAGE__,
                            function   => 'Bugzilla::Object->set' });

    my %validators = (%{$self->VALIDATORS}, %{$self->UPDATE_VALIDATORS});
    if (exists $validators{$field}) {
        my $validator = $validators{$field};
        $value = $self->$validator($value, $field);
        trick_taint($value) if (defined $value && !ref($value));

        if ($self->can('_set_global_validator')) {
            $self->_set_global_validator($value, $field);
        }
    }

    $self->{$field} = $value;
}

sub set_all {
    my ($self, $params) = @_;
    foreach my $key (keys %$params) {
        my $method = "set_$key";
        $self->$method($params->{$key});
    }
}

sub update {
    my $self = shift;

    my $dbh      = Bugzilla->dbh;
    my $table    = $self->DB_TABLE;
    my $id_field = $self->ID_FIELD;

    $dbh->bz_start_transaction();

    my $old_self = $self->new($self->id);
    
    my %numeric = map { $_ => 1 } $self->NUMERIC_COLUMNS;
    my %date    = map { $_ => 1 } $self->DATE_COLUMNS;
    my (@update_columns, @values, %changes);
    foreach my $column ($self->UPDATE_COLUMNS) {
        my ($old, $new) = ($old_self->{$column}, $self->{$column});
        # This has to be written this way in order to allow us to set a field
        # from undef or to undef, and avoid warnings about comparing an undef
        # with the "eq" operator.
        if (!defined $new || !defined $old) {
            next if !defined $new && !defined $old;
        }
        elsif ( ($numeric{$column} && $old == $new) 
                || ($date{$column} && str2time($old) == str2time($new))
                || $old eq $new ) {
            next;
        }

        trick_taint($new) if defined $new;
        push(@values, $new);
        push(@update_columns, $column);
        # We don't use $new because we don't want to detaint this for
        # the caller.
        $changes{$column} = [$old, $self->{$column}];
    }

    my $columns = join(', ', map {"$_ = ?"} @update_columns);

    $dbh->do("UPDATE $table SET $columns WHERE $id_field = ?", undef, 
             @values, $self->id) if @values;

    $dbh->bz_commit_transaction();

    if (wantarray) {
        return (\%changes, $old_self);
    }

    return \%changes;
}

sub remove_from_db {
    my $self = shift;
    my $table = $self->DB_TABLE;
    my $id_field = $self->ID_FIELD;
    Bugzilla->dbh->do("DELETE FROM $table WHERE $id_field = ?",
                      undef, $self->id);
    undef $self;
}

###############################
####      Subroutines    ######
###############################

sub any_exist {
    my $class = shift;
    my $table = $class->DB_TABLE;
    my $dbh = Bugzilla->dbh;
    my $any_exist = $dbh->selectrow_array(
        "SELECT 1 FROM $table " . $dbh->sql_limit(1));
    return $any_exist ? 1 : 0;
}

sub create {
    my ($class, $params) = @_;
    my $dbh = Bugzilla->dbh;

    $dbh->bz_start_transaction();
    $class->check_required_create_fields($params);
    my $field_values = $class->run_create_validators($params);
    my $object = $class->insert_create_data($field_values);
    $dbh->bz_commit_transaction();

    return $object;
}

# Used to validate that a field name is in fact a valid column in the
# current table before inserting it into SQL.
sub _check_field {
    my ($invocant, $field, $function) = @_;
    my $class = ref($invocant) || $invocant;
    if (!Bugzilla->dbh->bz_column_info($class->DB_TABLE, $field)) {
        ThrowCodeError('param_invalid', { param    => $field,
                                          function => "${class}::$function" });
    }
}

sub check_required_create_fields {
    my ($class, $params) = @_;

    foreach my $field ($class->REQUIRED_CREATE_FIELDS) {
        ThrowCodeError('param_required',
            { function => "${class}->create", param => $field })
            if !exists $params->{$field};
    }
}

sub run_create_validators {
    my ($class, $params) = @_;

    my $validators = $class->VALIDATORS;

    my %field_values;
    # We do the sort just to make sure that validation always
    # happens in a consistent order.
    foreach my $field (sort keys %$params) {
        my $value;
        if (exists $validators->{$field}) {
            my $validator = $validators->{$field};
            $value = $class->$validator($params->{$field}, $field);
        }
        else {
            $value = $params->{$field};
        }
        # We want people to be able to explicitly set fields to NULL,
        # and that means they can be set to undef.
        trick_taint($value) if defined $value && !ref($value);
        $field_values{$field} = $value;
    }

    return \%field_values;
}

sub insert_create_data {
    my ($class, $field_values) = @_;
    my $dbh = Bugzilla->dbh;

    my (@field_names, @values);
    while (my ($field, $value) = each %$field_values) {
        $class->_check_field($field, 'create');
        push(@field_names, $field);
        push(@values, $value);
    }

    my $qmarks = '?,' x @field_names;
    chop($qmarks);
    my $table = $class->DB_TABLE;
    $dbh->do("INSERT INTO $table (" . join(', ', @field_names)
             . ") VALUES ($qmarks)", undef, @values);
    my $id = $dbh->bz_last_key($table, $class->ID_FIELD);
    return $class->new($id);
}

sub get_all {
    my $class = shift;
    return @{$class->_do_list_select()};
}

###############################
####      Validators     ######
###############################

sub check_boolean { return $_[1] ? 1 : 0 }

1;

__END__

=head1 NAME

Bugzilla::Object - A base class for objects in Bugzilla.

=head1 SYNOPSIS

 my $object = new Bugzilla::Object(1);
 my $object = new Bugzilla::Object({name => 'TestProduct'});

 my $id          = $object->id;
 my $name        = $object->name;

=head1 DESCRIPTION

Bugzilla::Object is a base class for Bugzilla objects. You never actually
create a Bugzilla::Object directly, you only make subclasses of it.

Basically, Bugzilla::Object exists to allow developers to create objects
more easily. All you have to do is define C<DB_TABLE>, C<DB_COLUMNS>,
and sometimes C<LIST_ORDER> and you have a whole new object.

You should also define accessors for any columns other than C<name>
or C<id>.

=head1 CONSTANTS

Frequently, these will be the only things you have to define in your
subclass in order to have a fully-functioning object. C<DB_TABLE>
and C<DB_COLUMNS> are required.

=over

=item C<DB_TABLE>

The name of the table that these objects are stored in. For example,
for C<Bugzilla::Keyword> this would be C<keyworddefs>.

=item C<DB_COLUMNS>

The names of the columns that you want to read out of the database
and into this object. This should be an array.

=item C<NAME_FIELD>

The name of the column that should be considered to be the unique
"name" of this object. The 'name' is a B<string> that uniquely identifies
this Object in the database. Defaults to 'name'. When you specify 
C<{name => $name}> to C<new()>, this is the column that will be 
matched against in the DB.

=item C<ID_FIELD>

The name of the column that represents the unique B<integer> ID
of this object in the database. Defaults to 'id'.

=item C<LIST_ORDER>

The order that C<new_from_list> and C<get_all> should return objects
in. This should be the name of a database column. Defaults to
L</NAME_FIELD>.

=item C<REQUIRED_CREATE_FIELDS>

The list of fields that B<must> be specified when the user calls
C<create()>. This should be an array.

=item C<VALIDATORS>

A hashref that points to a function that will validate each param to
L</create>. 

Validators are called both by L</create> and L</set>. When
they are called by L</create>, the first argument will be the name
of the class (what we normally call C<$class>).

When they are called by L</set>, the first argument will be
a reference to the current object (what we normally call C<$self>).

The second argument will be the value passed to L</create> or 
L</set>for that field. 

The third argument will be the name of the field being validated.
This may be required by validators which validate several distinct fields.

These functions should call L<Bugzilla::Error/ThrowUserError> if they fail.

The validator must return the validated value.

=item C<UPDATE_VALIDATORS>

This is just like L</VALIDATORS>, but these validators are called only
when updating an object, not when creating it. Any validator that appears
here must not appear in L</VALIDATORS>.

L<Bugzilla::Bug> has good examples in its code of when to use this.

=item C<UPDATE_COLUMNS>

A list of columns to update when L</update> is called.
If a field can't be changed, it shouldn't be listed here. (For example,
the L</ID_FIELD> usually can't be updated.)

=item C<NUMERIC_COLUMNS>

When L</update> is called, it compares each column in the object to its
current value in the database. It only updates columns that have changed.

Any column listed in NUMERIC_COLUMNS is treated as a number, not as a string,
during these comparisons.

=item C<DATE_COLUMNS>

This is much like L</NUMERIC_COLUMNS>, except that it treats strings as
dates when being compared. So, for example, C<2007-01-01> would be
equal to C<2007-01-01 00:00:00>.

=back

=head1 METHODS

=head2 Constructors

=over

=item C<new>

=over

=item B<Description>

The constructor is used to load an existing object from the database,
by id or by name.

=item B<Params>

If you pass an integer, the integer is the id of the object, 
from the database, that we  want to read in. (id is defined
as the value in the L</ID_FIELD> column).

If you pass in a hashref, you can pass a C<name> key. The 
value of the C<name> key is the case-insensitive name of the object 
(from L</NAME_FIELD>) in the DB. You can also pass in an C<id> key
which will be interpreted as the id of the object you want (overriding the 
C<name> key).

B<Additional Parameters Available for Subclasses>

If you are a subclass of C<Bugzilla::Object>, you can pass
C<condition> and C<values> as hash keys, instead of the above.

C<condition> is a set of SQL conditions for the WHERE clause, which contain
placeholders.

C<values> is a reference to an array. The array contains the values
for each placeholder in C<condition>, in order.

This is to allow subclasses to have complex parameters, and then to
translate those parameters into C<condition> and C<values> when they
call C<$self->SUPER::new> (which is this function, usually).

If you try to call C<new> outside of a subclass with the C<condition>
and C<values> parameters, Bugzilla will throw an error. These parameters
are intended B<only> for use by subclasses.

=item B<Returns>

A fully-initialized object, or C<undef> if there is no object in the
database matching the parameters you passed in.

=back

=item C<check>

=over

=item B<Description>

Checks if there is an object in the database with the specified name, and
throws an error if you specified an empty name, or if there is no object
in the database with that name.

=item B<Params>

The parameters are the same as for L</new>, except that if you don't pass
a hashref, the single argument is the I<name> of the object, not the id.

=item B<Returns>

A fully initialized object, guaranteed.

=item B<Notes For Implementors>

If you implement this in your subclass, make sure that you also update
the C<object_name> block at the bottom of the F<global/user-error.html.tmpl>
template.

=back

=item C<new_from_list(\@id_list)>

 Description: Creates an array of objects, given an array of ids.

 Params:      \@id_list - A reference to an array of numbers, database ids.
                          If any of these are not numeric, the function
                          will throw an error. If any of these are not
                          valid ids in the database, they will simply 
                          be skipped.

 Returns:     A reference to an array of objects.

=item C<match>

=over

=item B<Description>

Gets a list of objects from the database based on certain criteria.

Basically, a simple way of doing a sort of "SELECT" statement (like SQL)
to get objects.

All criteria are joined by C<AND>, so adding more criteria will give you
a smaller set of results, not a larger set.

=item B<Params>

A hashref, where the keys are column names of the table, pointing to the 
value that you want to match against for that column. 

There are two special values, the constants C<NULL> and C<NOT_NULL>,
which means "give me objects where this field is NULL or NOT NULL,
respectively."

In addition to the column keys, there are a few special keys that
can be used to rig the underlying database queries. These are 
C<LIMIT>, C<OFFSET>, and C<WHERE>.

The value for the C<LIMIT> key is expected to be an integer defining 
the number of objects to return, while the value for C<OFFSET> defines
the position, relative to the number of objects the query would normally 
return, at which to begin the result set. If C<OFFSET> is defined without 
a corresponding C<LIMIT> it is silently ignored.

The C<WHERE> key provides a mechanism for adding arbitrary WHERE
clauses to the underlying query. Its value is expected to a hash 
reference whose keys are the columns, operators and placeholders, and the 
values are the placeholders' bind value. For example:

 WHERE => { 'some_column >= ?' => $some_value }

would constrain the query to only those objects in the table whose
'some_column' column has a value greater than or equal to $some_value.

If you don't specify any criteria, calling this function is the same
as doing C<[$class-E<gt>get_all]>.

=item B<Returns>

An arrayref of objects, or an empty arrayref if there are no matches.

=back

=back

=head2 Database Manipulation

=over

=item C<create>

Description: Creates a new item in the database.
             Throws a User Error if any of the passed-in params
             are invalid.

Params:      C<$params> - hashref - A value to put in each database
               field for this object. Certain values must be set (the 
               ones specified in L</REQUIRED_CREATE_FIELDS>), and
               the function will throw a Code Error if you don't set
               them.

Returns:     The Object just created in the database.

Notes:       In order for this function to work in your subclass,
             your subclass's L</ID_FIELD> must be of C<SERIAL>
             type in the database. Your subclass also must
             define L</REQUIRED_CREATE_FIELDS> and L</VALIDATORS>.

             Subclass Implementors: This function basically just
             calls L</check_required_create_fields>, then
             L</run_create_validators>, and then finally
             L</insert_create_data>. So if you have a complex system that
             you need to implement, you can do it by calling these
             three functions instead of C<SUPER::create>.

=item C<check_required_create_fields>

=over

=item B<Description>

Part of L</create>. Throws an error if any of the L</REQUIRED_CREATE_FIELDS>
have not been specified in C<$params>

=item B<Params>

=over

=item C<$params> - The same as C<$params> from L</create>.

=back

=item B<Returns> (nothing)

=back

=item C<run_create_validators>

Description: Runs the validation of input parameters for L</create>.
             This subroutine exists so that it can be overridden
             by subclasses who need to do special validations
             of their input parameters. This method is B<only> called
             by L</create>.

Params:      The same as L</create>.

Returns:     A hash, in a similar format as C<$params>, except that
             these are the values to be inserted into the database,
             not the values that were input to L</create>.

=item C<insert_create_data>

Part of L</create>.

Takes the return value from L</run_create_validators> and inserts the
data into the database. Returns a newly created object. 

=item C<update>

=over

=item B<Description>

Saves the values currently in this object to the database.
Only the fields specified in L</UPDATE_COLUMNS> will be
updated, and they will only be updated if their values have changed.

=item B<Params> (none)

=item B<Returns>

B<In scalar context:>

A hashref showing what changed during the update. The keys are the column
names from L</UPDATE_COLUMNS>. If a field was not changed, it will not be
in the hash at all. If the field was changed, the key will point to an arrayref.
The first item of the arrayref will be the old value, and the second item
will be the new value.

If there were no changes, we return a reference to an empty hash.

B<In array context:>

Returns a list, where the first item is the above hashref. The second item
is the object as it was in the database before update() was called. (This
is mostly useful to subclasses of C<Bugzilla::Object> that are implementing
C<update>.)

=back

=item C<remove_from_db>

Removes this object from the database. Will throw an error if you can't
remove it for some reason. The object will then be destroyed, as it is
not safe to use the object after it has been removed from the database.

=back

=head2 Mutators

These are used for updating the values in objects, before calling
C<update>.

=over

=item C<set>

=over

=item B<Description>

Sets a certain hash member of this class to a certain value.
Used for updating fields. Calls the validator for this field,
if it exists. Subclasses should use this function
to implement the various C<set_> mutators for their different
fields.

If your class defines a method called C<_set_global_validator>,
C<set> will call it with C<($value, $field)> as arguments, after running
the validator for this particular field. C<_set_global_validator> does not
return anything.

See L</VALIDATORS> for more information.

B<NOTE>: This function is intended only for use by subclasses. If
you call it from anywhere else, it will throw a C<CodeError>.

=item B<Params>

=over

=item C<$field> - The name of the hash member to update. This should
be the same as the name of the field in L</VALIDATORS>, if it exists there.

=item C<$value> - The value that you're setting the field to.

=back

=item B<Returns> (nothing)

=back


=item C<set_all>

=over

=item B<Description>

This is a convenience function which is simpler than calling many different
C<set_> functions in a row. You pass a hashref of parameters and it calls
C<set_$key($value)> for every item in the hashref.

=item B<Params>

Takes a hashref of the fields that need to be set, pointing to the value
that should be passed to the C<set_> function that is called.

=item B<Returns> (nothing)

=back


=back

=head2 Simple Validators

You can use these in your subclass L</VALIDATORS> or L</UPDATE_VALIDATORS>.
Note that you have to reference them like C<\&Bugzilla::Object::check_boolean>,
you can't just write C<\&check_boolean>.

=over

=item C<check_boolean>

Returns C<1> if the passed-in value is true, C<0> otherwise.

=back

=head1 CLASS FUNCTIONS

=over

=item C<any_exist>

Returns C<1> if there are any of these objects in the database,
C<0> otherwise.

=item C<get_all>

 Description: Returns all objects in this table from the database.

 Params:      none.

 Returns:     A list of objects, or an empty list if there are none.

 Notes:       Note that you must call this as C<$class->get_all>. For 
              example, C<Bugzilla::Keyword->get_all>. 
              C<Bugzilla::Keyword::get_all> will not work.

=back

=cut