package DBIx::Custom;

our $VERSION = '0.1643';

use 5.008001;

use strict;

use warnings;

use base 'Object::Simple';

use Carp 'croak';

use DBI;

use DBIx::Custom::Result;

use DBIx::Custom::Query;

use DBIx::Custom::QueryBuilder;

use DBIx::Custom::Where;

use DBIx::Custom::Table;

use DBIx::Custom::Tag;

use Encode qw/encode_utf8 decode_utf8/;

__PACKAGE__->attr(

    [qw/data_source dbh password user/],

    cache => 1,

    dbi_option    => sub { {} },

    query_builder => sub { DBIx::Custom::QueryBuilder->new },

    result_class  => 'DBIx::Custom::Result',

    base_table    => sub { DBIx::Custom::Table->new(dbi => shift) },

    safety_column_name => sub { qr/^[\w\.]*$/ },

    stash => sub { {} }

);

__PACKAGE__->attr(

    cache_method => sub {

        sub {

            my $self = shift;

            $self->{_cached} ||= {};

            if (@_ > 1) {

                $self->{_cached}{$_[0]} = $_[1] 

            }

            else {

                return $self->{_cached}{$_[0]}

            }

        }

    }

);

__PACKAGE__->attr(

    filters => sub {

        {

            encode_utf8 => sub { encode_utf8($_[0]) },

            decode_utf8 => sub { decode_utf8($_[0]) }

        }

    }

);

our $AUTOLOAD;

sub AUTOLOAD {

    my $self = shift;

    # Method name

    my ($package, $mname) = $AUTOLOAD =~ /^([\w\:]+)\:\:(\w+)$/;

    # Method

    $self->{_methods} ||= {};

    my $method = $self->{_methods}->{$mname};

    return $self->$method(@_) if $method;

    # DBI method

    return $self->dbh->$mname(@_);

}

sub apply_filter {

    my ($self, $table, @cinfos) = @_;

    # Initialize filters

    $self->{filter} ||= {};

    $self->{filter}{out} ||= {};

    $self->{filter}{in} ||= {};

    # Create filters

    my $usage = "Usage: \$dbi->apply_filter(" .

                "TABLE, COLUMN1, {in => INFILTER1, out => OUTFILTER1, end => ENDFILTER1}, " .

                "COLUMN2, {in => INFILTER2, out => OUTFILTER2, end => ENDFILTER2}, ...)";

    for (my $i = 0; $i < @cinfos; $i += 2) {

        # Column

        my $column = $cinfos[$i];

        # Filter info

        my $finfo = $cinfos[$i + 1] || {};

        croak $usage unless  ref $finfo eq 'HASH';

        foreach my $ftype (keys %$finfo) {

            croak $usage unless $ftype eq 'in' || $ftype eq 'out'

                             || $ftype eq 'end'; 

        }

        foreach my $way (qw/in out end/) {

            my $filter = $finfo->{$way};

            # State

            my $state = !exists $finfo->{$way} ? 'not_exists'

                      : !defined $filter        ? 'not_defined'

                      : ref $filter eq 'CODE'   ? 'code'

                      : 'name';

            next if $state eq 'not_exists';

            # Check filter

            croak qq{Filter "$filter" is not registered}

              if  $state eq 'name'

               && ! exists $self->filters->{$filter};

            # Filter

            my $f = $state eq 'not_defined' ? undef

                  : $state eq 'code'        ? $filter

                  : $self->filters->{$filter};

            $self->{filter}{$way}{$table}{$column} = $f;

            $self->{filter}{$way}{$table}{"$table.$column"} = $f;

            $self->{filter}{$way}{$table}{"${table}__$column"} = $f;

        }

    }

    return $self;

}

sub method {

    my $self = shift;

    # Merge

    my $methods = ref $_[0] eq 'HASH' ? $_[0] : {@_};

    $self->{_methods} = {%{$self->{_methods} || {}}, %$methods};

    return $self;

}

sub connect {

    my $self = ref $_[0] ? shift : shift->new(@_);;

    # Attributes

    my $data_source = $self->data_source;

    croak qq{"data_source" must be specified to connect()"}

      unless $data_source;

    my $user        = $self->user;

    my $password    = $self->password;

    my $dbi_option = {%{$self->dbi_options}, %{$self->dbi_option}};

    # Connect

    my $dbh = eval {DBI->connect(

        $data_source,

        $user,

        $password,

        {

            RaiseError => 1,

            PrintError => 0,

            AutoCommit => 1,

            %$dbi_option

        }

    )};

    # Connect error

    croak $@ if $@;

    # Database handle

    $self->dbh($dbh);

    return $self;

}

sub create_query {

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

    # Cache

    my $cache = $self->cache;

    # Create query

    my $query;

    if ($cache) {

        # Get query

        my $q = $self->cache_method->($self, $source);

        # Create query

        if ($q) {

            $query = DBIx::Custom::Query->new($q);

            $query->filters($self->filters);

        }

    }

    unless ($query) {

        # Create SQL object

        my $builder = $self->query_builder;

        # Create query

        $query = $builder->build_query($source);

        # Cache query

        $self->cache_method->($self, $source,

                             {sql     => $query->sql, 

                              columns => $query->columns,

                              tables  => $query->tables})

          if $cache;

    }

    # Prepare statement handle

    my $sth;

    eval { $sth = $self->dbh->prepare($query->{sql})};

    $self->_croak($@, qq{. Following SQL is executed. "$query->{sql}"}) if $@;

    # Set statement handle

    $query->sth($sth);

    # Set filters

    $query->filters($self->filters);

    return $query;

}

our %VALID_DELETE_ARGS

  = map { $_ => 1 } qw/table where append filter allow_delete_all query/;

sub delete {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_DELETE_ARGS{$name};

    }

    # Arguments

    my $table            = $args{table} || '';

    croak qq{"table" option must be specified} unless $table;

    my $where            = $args{where} || {};

    my $append           = $args{append};

    my $filter           = $args{filter};

    my $allow_delete_all = $args{allow_delete_all};

    # Where

    my $w;

    if (ref $where eq 'HASH') {

        my $clause = ['and'];

        push @$clause, "{= $_}" for keys %$where;

        $w = $self->where;

        $w->clause($clause);

        $w->param($where);

    }

    elsif (ref $where eq 'DBIx::Custom::Where') {

        $w = $where;

        $where = $w->param;

    }    

    croak qq{"where" must be hash refernce or DBIx::Custom::Where object}

      unless ref $w eq 'DBIx::Custom::Where';

    # String where

    my $swhere = "$w";

    croak qq{"where" must be specified}

      if $swhere eq '' && !$allow_delete_all;

    # SQL stack

    my @sql;

    # Delete

    push @sql, "delete from $table $swhere";

    push @sql, $append if $append;

    my $sql = join(' ', @sql);

    # Create query

    my $query = $self->create_query($sql);

    return $query if $args{query};

    # Execute query

    my $ret_val = $self->execute(

        $query, param  => $where, filter => $filter,

        table => $table);

    return $ret_val;

}

sub delete_all { shift->delete(allow_delete_all => 1, @_) }

sub DESTROY { }

our %VALID_EXECUTE_ARGS = map { $_ => 1 } qw/param filter table/;

sub execute{

    my ($self, $query, %args)  = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_EXECUTE_ARGS{$name};

    }

    my $params = $args{param} || {};

    # First argument is the soruce of SQL

    $query = $self->create_query($query)

      unless ref $query;

    # Applied filter

    my $filter = {};

    my $tables = $query->tables;

    my $arg_tables = $args{table} || [];

    $arg_tables = [$arg_tables]

      unless ref $arg_tables eq 'ARRAY';

    push @$tables, @$arg_tables;

    foreach my $table (@$tables) {

        $filter = {

            %$filter,

            %{$self->{filter}{out}->{$table} || {}}

        }

    }

    # Filter argument

    my $f = $args{filter} || $query->filter || {};

    foreach my $column (keys %$f) {

        my $fname = $f->{$column};

        if (!defined $fname) {

            $f->{$column} = undef;

        }

        elsif (ref $fname ne 'CODE') {

          croak qq{Filter "$fname" is not registered"}

            unless exists $self->filters->{$fname};

          $f->{$column} = $self->filters->{$fname};

        }

    }

    $filter = {%$filter, %$f};

    # Bind

    my $bind = $self->_bind($params, $query->columns, $filter);

    # Execute

    my $sth = $query->sth;

    my $affected;

    eval {$affected = $sth->execute(@$bind)};

    $self->_croak($@, qq{. Following SQL is executed. "$query->{sql}"}) if $@;

    # Return resultset if select statement is executed

    if ($sth->{NUM_OF_FIELDS}) {

        # Result in and end filter

        my $in_filter  = {};

        my $end_filter = {};

        foreach my $table (@$tables) {

            $in_filter = {

                %$in_filter,

                %{$self->{filter}{in}{$table} || {}}

            };

            $end_filter = {

                %$end_filter,

                %{$self->{filter}{end}{$table} || {}}

            };

        }

        # Result

        my $result = $self->result_class->new(

            sth            => $sth,

            filters        => $self->filters,

            filter_check   => $self->filter_check,

            default_filter => $self->{default_in_filter},

            filter         => $in_filter || {},

            end_filter     => $end_filter || {}

        );

        return $result;

    }

    return $affected;

}

our %VALID_INSERT_ARGS = map { $_ => 1 } qw/table param append

                                            filter query/;

sub insert {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_INSERT_ARGS{$name};

    }

    # Arguments

    my $table  = $args{table};

    croak qq{"table" option must be specified} unless $table;

    my $param  = $args{param} || {};

    my $append = $args{append} || '';

    my $filter = $args{filter};

    # Columns

    my @columns;

    my $safety = $self->safety_column_name;

    foreach my $column (keys %$param) {

        croak qq{"$column" is not safety column name}

          unless $column =~ /$safety/;

        push @columns, $column;

    }

    # SQL stack

    my @sql;

    # Insert

    push @sql, "insert into $table {insert_param ". join(' ', @columns) . '}';

    push @sql, $append if $append;

    # SQL

    my $sql = join (' ', @sql);

    # Create query

    my $query = $self->create_query($sql);

    return $query if $args{query};

    # Execute query

    my $ret_val = $self->execute(

        $query,

        param  => $param,

        filter => $filter,

        table => $table

    );

    return $ret_val;

}

sub each_column {

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

    # Iterate all tables

    my $sth_tables = $self->dbh->table_info;

    while (my $table_info = $sth_tables->fetchrow_hashref) {

        # Table

        my $table = $table_info->{TABLE_NAME};

        # Iterate all columns

        my $sth_columns = $self->dbh->column_info(undef, undef, $table, '%');

        while (my $column_info = $sth_columns->fetchrow_hashref) {

            my $column = $column_info->{COLUMN_NAME};

            $self->$cb($table, $column, $column_info);

        }

    }

}

sub new {

    my $self = shift->SUPER::new(@_);

    # Check attribute names

    my @attrs = keys %$self;

    foreach my $attr (@attrs) {

        croak qq{"$attr" is invalid attribute name}

          unless $self->can($attr);

    }

    $self->register_tag(

        '?'     => \&DBIx::Custom::Tag::placeholder,

        '='     => \&DBIx::Custom::Tag::equal,

        '<>'    => \&DBIx::Custom::Tag::not_equal,

        '>'     => \&DBIx::Custom::Tag::greater_than,

        '<'     => \&DBIx::Custom::Tag::lower_than,

        '>='    => \&DBIx::Custom::Tag::greater_than_equal,

        '<='    => \&DBIx::Custom::Tag::lower_than_equal,

        'like'  => \&DBIx::Custom::Tag::like,

        'in'    => \&DBIx::Custom::Tag::in,

        'insert_param' => \&DBIx::Custom::Tag::insert_param,

        'update_param' => \&DBIx::Custom::Tag::update_param

    );

    return $self;

}

sub not_exists { bless {}, 'DBIx::Custom::NotExists' }

sub register_filter {

    my $invocant = shift;

    # Register filter

    my $filters = ref $_[0] eq 'HASH' ? $_[0] : {@_};

    $invocant->filters({%{$invocant->filters}, %$filters});

    return $invocant;

}

sub register_tag { shift->query_builder->register_tag(@_) }

our %VALID_SELECT_ARGS

  = map { $_ => 1 } qw/table column where append relation filter query/;

sub select {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_SELECT_ARGS{$name};

    }

    # Arguments

    my $table = $args{table};

    my $tables = ref $table eq 'ARRAY' ? $table

               : defined $table ? [$table]

               : [];

    croak qq{"table" option must be specified} unless @$tables;

    my $columns  = $args{column} || [];

    my $where    = $args{where} || {};

    my $relation = $args{relation};

    my $append   = $args{append};

    my $filter   = $args{filter};

    # SQL stack

    my @sql;

    push @sql, 'select';

    # Column clause

    if (@$columns) {

        foreach my $column (@$columns) {

            push @sql, ($column, ',');

        }

        pop @sql if $sql[-1] eq ',';

    }

    else { push @sql, '*' }

    # Table

    push @sql, 'from';

    foreach my $table (@$tables) {

        push @sql, ($table, ',');

    }

    pop @sql if $sql[-1] eq ',';

    # Where

    my $w;

    if (ref $where eq 'HASH') {

        my $clause = ['and'];

        push @$clause, "{= $_}" for keys %$where;

        $w = $self->where;

        $w->clause($clause);

        $w->param($where);

    }

    elsif (ref $where eq 'DBIx::Custom::Where') {

        $w = $where;

        $where = $w->param;

    }

    croak qq{"where" must be hash reference or DBIx::Custom::Where object}

      unless ref $w eq 'DBIx::Custom::Where';

    # String where

    my $swhere = "$w";

    push @sql, $swhere;

    # Relation

    if ($relation) {

        push @sql, $swhere eq '' ? 'where' : 'and';

        foreach my $rcolumn (keys %$relation) {

            push @sql, ("$rcolumn = " . $relation->{$rcolumn},  'and');

        }

    }

    pop @sql if $sql[-1] eq 'and';

    # Append statement

    push @sql, $append if $append;

    # SQL

    my $sql = join (' ', @sql);

    # Create query

    my $query = $self->create_query($sql);

    return $query if $args{query};

    # Execute query

    my $result = $self->execute(

        $query, param  => $where, filter => $filter,

        table => $tables);

    return $result;

}

sub table {

    my $self = shift;

    my $name = shift;

    # Create table

    $self->{_tables} ||= {};

    unless (defined $self->{_tables}->{$name}) {

        # Base table

        my $base_table = $self->base_table;

        # Base methods

        my $bmethods = ref $base_table->{_methods} eq 'HASH'

                     ? $base_table->{_methods}

                     : {};

        # Copy Methods

        my $methods = {};

        $methods->{$_} = $bmethods->{$_} for keys %$bmethods;

        $methods->{"base_$_"} = $bmethods->{$_} for keys %$bmethods;

        # Create table

        my $table = $base_table->new(

            dbi      => $self,

            name     => $name,

        );

        $table->method($methods);

        $self->{_tables}->{$name} = $table;

    }

    return $self->{_tables}{$name};

}

our %VALID_UPDATE_ARGS

  = map { $_ => 1 } qw/table param

                       where append filter allow_update_all query/;

sub update {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_UPDATE_ARGS{$name};

    }

    # Arguments

    my $table            = $args{table} || '';

    croak qq{"table" option must be specified} unless $table;

    my $param            = $args{param} || {};

    my $where            = $args{where} || {};

    my $append           = $args{append} || '';

    my $filter           = $args{filter};

    my $allow_update_all = $args{allow_update_all};

    # Update keys

    my @clumns = keys %$param;

    # Columns

    my @columns;

    my $safety = $self->safety_column_name;

    foreach my $column (keys %$param) {

        croak qq{"$column" is not safety column name}

          unless $column =~ /$safety/;

        push @columns, $column;

    }

    # Update clause

    my $update_clause = '{update_param ' . join(' ', @clumns) . '}';

    # Where

    my $w;

    if (ref $where eq 'HASH') {

        my $clause = ['and'];

        push @$clause, "{= $_}" for keys %$where;

        $w = $self->where;

        $w->clause($clause);

        $w->param($where);

    }

    elsif (ref $where eq 'DBIx::Custom::Where') {

        $w = $where;

        $where = $w->param;

    }  

    croak qq{"where" must be hash refernce or DBIx::Custom::Where object}

      unless ref $w eq 'DBIx::Custom::Where';

    # String where

    my $swhere = "$w";

    croak qq{"where" must be specified}

      if "$swhere" eq '' && !$allow_update_all;

    # SQL stack

    my @sql;

    # Update

    push @sql, "update $table $update_clause $swhere";

    push @sql, $append if $append;

    # Rearrange parameters

    foreach my $wkey (keys %$where) {

        if (exists $param->{$wkey}) {

            $param->{$wkey} = [$param->{$wkey}]

              unless ref $param->{$wkey} eq 'ARRAY';

            push @{$param->{$wkey}}, $where->{$wkey};

        }

        else {

            $param->{$wkey} = $where->{$wkey};

        }

    }

    # SQL

    my $sql = join(' ', @sql);

    # Create query

    my $query = $self->create_query($sql);

    return $query if $args{query};

    # Execute query

    my $ret_val = $self->execute($query, param  => $param, 

                                 filter => $filter,

                                 table => $table);

    return $ret_val;

}

sub update_all { shift->update(allow_update_all => 1, @_) };

sub where {

    my $self = shift;

    return DBIx::Custom::Where->new(

        query_builder => $self->query_builder,

        safety_column_name => $self->safety_column_name

    );

}

sub _bind {

    my ($self, $params, $columns, $filter) = @_;

    # bind values

    my @bind;

    # Build bind values

    my $count = {};

    my $not_exists = {};

    foreach my $column (@$columns) {

        # Value

        my $value;

        if(ref $params->{$column} eq 'ARRAY') {

            my $i = $count->{$column} || 0;

            $i += $not_exists->{$column} || 0;

            my $found;

            for (my $k = $i; $i < @{$params->{$column}}; $k++) {

                if (ref $params->{$column}->[$k] eq 'DBIx::Custom::NotExists') {

                    $not_exists->{$column}++;

                }

                else  {

                    $value = $params->{$column}->[$k];

                    $found = 1;

                    last

                }

            }

            next unless $found;

        }

        else { $value = $params->{$column} }

        # Filter

        my $f = $filter->{$column} || $self->{default_out_filter} || '';

        push @bind, $f ? $f->($value) : $value;

        # Count up 

        $count->{$column}++;

    }

    return \@bind;

}

sub _croak {

    my ($self, $error, $append) = @_;

    $append ||= "";

    # Verbose

    if ($Carp::Verbose) { croak $error }

    # Not verbose

    else {

        # Remove line and module infromation

        my $at_pos = rindex($error, ' at ');

        $error = substr($error, 0, $at_pos);

        $error =~ s/\s+$//;

        croak "$error$append";

    }

}

# DEPRECATED!

__PACKAGE__->attr(

    dbi_options => sub { {} },

    filter_check  => 1

);

# DEPRECATED!

sub default_bind_filter {

    my $self = shift;

    if (@_) {

        my $fname = $_[0];

        if (@_ && !$fname) {

            $self->{default_out_filter} = undef;

        }

        else {

            croak qq{Filter "$fname" is not registered}

              unless exists $self->filters->{$fname};

            $self->{default_out_filter} = $self->filters->{$fname};

        }

        return $self;

    }

    return $self->{default_out_filter};

}

# DEPRECATED!

sub default_fetch_filter {

    my $self = shift;

    if (@_) {

        my $fname = $_[0];

        if (@_ && !$fname) {

            $self->{default_in_filter} = undef;

        }

        else {

            croak qq{Filter "$fname" is not registered}

              unless exists $self->filters->{$fname};

            $self->{default_in_filter} = $self->filters->{$fname};

        }

        return $self;

    }

    return $self->{default_in_filter};

}

# DEPRECATED!

sub register_tag_processor {

    return shift->query_builder->register_tag_processor(@_);

}

1;

=head1 NAME

DBIx::Custom - DBI interface, having hash parameter binding and filtering system

=head1 SYNOPSYS

    use DBIx::Custom;

    my $dbi = DBIx::Custom->connect(data_source => "dbi:mysql:database=dbname",

                                    user => 'ken', password => '!LFKD%$&',

                                    dbi_option => {mysql_enable_utf8 => 1});

    # Insert 

    $dbi->insert(table  => 'book',

                 param  => {title => 'Perl', author => 'Ken'},

                 filter => {title => 'to_something'});

    # Update 

    $dbi->update(table  => 'book', 

                 param  => {title => 'Perl', author => 'Ken'}, 

                 where  => {id => 5},

                 filter => {title => 'to_something'});

    # Update all

    $dbi->update_all(table  => 'book',

                     param  => {title => 'Perl'},

                     filter => {title => 'to_something'});

    # Delete

    $dbi->delete(table  => 'book',

                 where  => {author => 'Ken'},

                 filter => {title => 'to_something'});

    # Delete all

    $dbi->delete_all(table => 'book');

    # Select

    my $result = $dbi->select(

        table  => 'book',

        column => [qw/author title/],

        where  => {author => 'Ken'},

        relation => {'book.id' => 'rental.book_id'},

        append => 'order by id limit 5',

        filter => {title => 'to_something'}

    );

    # Execute SQL

    $dbi->execute("select title from book");

    # Execute SQL with hash binding and filtering

    $dbi->execute("select id from book where {= author} and {like title}",

                  param  => {author => 'ken', title => '%Perl%'},

                  filter => {title => 'to_something'});

    # Create query and execute it

    my $query = $dbi->create_query(

        "select id from book where {= author} and {like title}"

    );

    $dbi->execute($query, param => {author => 'Ken', title => '%Perl%'})

    # Get DBI object

    my $dbh = $dbi->dbh;

    # Fetch

    while (my $row = $result->fetch) {

        # ...

    }

    # Fetch hash

    while (my $row = $result->fetch_hash) {

    }

=head1 DESCRIPTIONS

L<DBIx::Custom> is one of L<DBI> interface modules,

such as L<DBIx::Class>, L<DBIx::Simple>.

This module is not O/R mapper. O/R mapper is useful,

but you must learn many syntax of the O/R mapper,

which is almost another language.

Created SQL statement is offten not effcient and damage SQL performance.

so you have to execute raw SQL in the end.

L<DBIx::Custom> is middle area between L<DBI> and O/R mapper.

L<DBIx::Custom> provide flexible hash parameter binding and filtering system,

and suger methods, such as C<insert()>, C<update()>, C<delete()>, C<select()>

to execute SQL easily.

L<DBIx::Custom> respects SQL. SQL is very complex and not beautiful,

but de-facto standard,

so all people learing database know it.

If you already know SQL,

you learn a little thing to use L<DBIx::Custom>.

See L<DBIx::Custom::Guide> for more details.

=head1 GUIDE

L<DBIx::Custom::Guide> - L<DBIx::Custom> complete guide

=head1 EXAMPLES

L<DBIx::Custom Wiki|https://github.com/yuki-kimoto/DBIx-Custom/wiki> - Many useful examples

=head1 ATTRIBUTES

=head2 C<cache>

    my $cache = $dbi->cache;

    $dbi      = $dbi->cache(1);

Enable parsed L<DBIx::Custom::Query> object caching.

Default to 1.

=head2 C<data_source>

    my $data_source = $dbi->data_source;

    $dbi            = $dbi->data_source("DBI:mysql:database=dbname");

Data source.

C<connect()> method use this value to connect the database.

=head2 C<dbh>

    my $dbh = $dbi->dbh;

    $dbi    = $dbi->dbh($dbh);

L<DBI> object. You can call all methods of L<DBI>.

=head2 C<dbi_option>

    my $dbi_option = $dbi->dbi_option;

    $dbi            = $dbi->dbi_option($dbi_option);

DBI options.

C<connect()> method use this value to connect the database.

Default filter when row is fetched.

=head2 C<filters>

    my $filters = $dbi->filters;

    $dbi        = $dbi->filters(\%filters);

=head2 C<password>

    my $password = $dbi->password;

    $dbi         = $dbi->password('lkj&le`@s');

Password.

C<connect()> method use this value to connect the database.

=head2 C<query_builder>

    my $sql_class = $dbi->query_builder;

    $dbi          = $dbi->query_builder(DBIx::Custom::QueryBuilder->new);

SQL builder. C<query_builder()> must be 

the instance of L<DBIx::Custom::QueryBuilder> subclass.

Default to L<DBIx::Custom::QueryBuilder> object.

=head2 C<result_class>