package DBIx::Custom;

our $VERSION = '0.1618';

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 Encode qw/encode_utf8 decode_utf8/;

__PACKAGE__->attr([qw/data_source dbh default_bind_filter

                      default_fetch_filter password user/]);

__PACKAGE__->attr(cache => 1);

__PACKAGE__->attr(cache_method => sub {

    sub {

        my $self = shift;

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

        if (@_ > 1) {

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

        }

        else {

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

        }

    }

});

__PACKAGE__->dual_attr('filters', default => sub { {} },

                                  inherit => 'hash_copy');

__PACKAGE__->attr(filter_check => 1);

__PACKAGE__->attr(query_builder  => sub {DBIx::Custom::QueryBuilder->new});

__PACKAGE__->attr(result_class => 'DBIx::Custom::Result');

# DBI methods

foreach my $method (qw/begin_work commit rollback/) {

    my $code = sub {

        my $self = shift;

        my $ret = eval {$self->dbh->$method};

        croak $@ if $@;

        return $ret;

    };

    no strict 'refs';

    my $pkg = __PACKAGE__;

    *{"${pkg}::$method"} = $code;

};

# Regster filter

__PACKAGE__->register_filter(

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

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

);

our $AUTOLOAD;

sub AUTOLOAD {

    my $self = shift;

    # Method

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

    # Helper

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

    croak qq/Can't locate object method "$method" via "$package"/

      unless my $helper = $self->{_helpers}->{$method};

    # Run

    return $self->$helper(@_);

}

sub helper {

    my $self = shift;

    # Merge

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

    $self->{_helpers} = {%{$self->{_helpers} || {}}, %$helpers};

    return $self;

}

sub connect {

    my $proto = shift;

    # Create

    my $self = ref $proto ? $proto : $proto->new(@_);

    # Information

    my $data_source = $self->data_source;

    my $user        = $self->user;

    my $password    = $self->password;

    # Connect

    my $dbh = eval {DBI->connect(

        $data_source,

        $user,

        $password,

        {

            RaiseError => 1,

            PrintError => 0,

            AutoCommit => 1,

        }

    )};

    # 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

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

    }

    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})

          if $cache;

    }

    # Prepare statement handle

    my $sth;

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

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

    # Set statement handle

    $query->sth($sth);

    return $query;

}

our %VALID_DELETE_ARGS

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

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} || '';

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

    my $append = $args{append};

    my $filter           = $args{filter};

    my $allow_delete_all = $args{allow_delete_all};

    # Where keys

    my @where_keys = keys %$where;

    # Not exists where keys

    croak qq{"where" argument must be specified and } .

          qq{contains the pairs of column name and value}

      if !@where_keys && !$allow_delete_all;

    # Where clause

    my $where_clause = '';

    if (@where_keys) {

        $where_clause = 'where ';

        $where_clause .= "{= $_} and " for @where_keys;

        $where_clause =~ s/ and $//;

    }

    # Source of SQL

    my $source = "delete from $table $where_clause";

    $source .= " $append" if $append;

    # Execute query

    my $ret_val = $self->execute($source, param  => $where, 

                                 filter => $filter);

    return $ret_val;

}

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

sub DESTROY { }

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

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;

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

    # Create bind value

    my $bind_values = $self->_build_bind_values($query, $params, $filter);

    # Execute

    my $sth      = $query->sth;

    my $affected;

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

    $self->_croak($@) if $@;

    # Return resultset if select statement is executed

    if ($sth->{NUM_OF_FIELDS}) {

        # Create result

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

            sth            => $sth,

            default_filter => $self->default_fetch_filter,

            filters        => $self->filters,

            filter_check   => $self->filter_check

        );

        return $result;

    }

    return $affected;

}

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

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} || '';

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

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

    my $filter = $args{filter};

    # Insert keys

    my @insert_keys = keys %$param;

    # Templte for insert

    my $source = "insert into $table {insert_param "

               . join(' ', @insert_keys) . '}';

    $source .= " $append" if $append;

    # Execute query

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

                                          filter => $filter);

    return $ret_val;

}

sub register_filter {

    my $invocant = shift;

    # Register filter

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

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

    return $invocant;

}

our %VALID_SELECT_ARGS

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

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 $tables = $args{table} || [];

    $tables = [$tables] unless ref $tables eq 'ARRAY';

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

    my $where    = $args{where};

    my $relation = $args{relation};

    my $append   = $args{append};

    my $filter   = $args{filter};

    # Source of SQL

    my $source = 'select ';

    # Column clause

    if (@$columns) {

        foreach my $column (@$columns) {

            $source .= "$column, ";

        }

        $source =~ s/, $/ /;

    }

    else {

        $source .= '* ';

    }

    # Table

    $source .= 'from ';

    foreach my $table (@$tables) {

        $source .= "$table, ";

    }

    $source =~ s/, $/ /;

    # Where clause

    my $param;

    if (ref $where eq 'HASH') {

        $param = $where;

        $source .= 'where (';

        foreach my $where_key (keys %$where) {

            $source .= "{= $where_key} and ";

        }

        $source =~ s/ and $//;

        $source .= ') ';

    }

    elsif (ref $where eq 'ARRAY') {

        my$where_str = $where->[0] || '';

        $param = $where->[1];

        $source .= "where ($where_str) ";

    }

    # Relation

    if ($relation) {

        $source .= $where ? "and " : "where ";

        foreach my $rkey (keys %$relation) {

            $source .= "$rkey = " . $relation->{$rkey} . " and ";

        }

    }

    $source =~ s/ and $//;

    # Append some statement

    $source .= " $append" if $append;

    # Execute query

    my $result = $self->execute($source, param  => $param, 

                                         filter => $filter);

    return $result;

}

our %VALID_UPDATE_ARGS

  = map { $_ => 1 } qw/table param where append filter allow_update_all/;

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} || '';

    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 @update_keys = keys %$param;

    # Where keys

    my @where_keys = keys %$where;

    # Not exists where keys

    croak qq{"where" argument must be specified and } .

          qq{contains the pairs of column name and value}

      if !@where_keys && !$allow_update_all;

    # Update clause

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

    # Where clause

    my $where_clause = '';

    my $new_where = {};

    if (@where_keys) {

        $where_clause = 'where ';

        $where_clause .= "{= $_} and " for @where_keys;

        $where_clause =~ s/ and $//;

    }

    # Source of SQL

    my $source = "update $table $update_clause $where_clause";

    $source .= " $append" if $append;

    # Rearrange parameters

    foreach my $wkey (@where_keys) {

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

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

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

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

        }

        else {

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

        }

    }

    # Execute query

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

                                 filter => $filter);

    return $ret_val;

}

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

sub _build_bind_values {

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

    # binding values

    my @bind_values;

    # Filter

    $filter ||= {};

    # Parameter

    $params ||= {};

    # Check filter

    $self->_check_filter($self->filters, $filter,

                         $self->default_bind_filter, $params)

      if $self->filter_check;

    # Build bind values

    my $count = {};

    foreach my $column (@{$query->columns}) {

        # Value

        my $value = ref $params->{$column} eq 'ARRAY'

                  ? $params->{$column}->[$count->{$column} || 0]

                  : $params->{$column};

        # Filtering

        my $fname = $filter->{$column} || $self->default_bind_filter || '';

        my $filter_func = $fname ? $self->filters->{$fname} : undef;

        push @bind_values, $filter_func

                         ? $filter_func->($value)

                         : $value;

        # Count up 

        $count->{$column}++;

    }

    return \@bind_values;

}

sub _check_filter {

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

    # Filter name not exists

    foreach my $fname (values %$filter) {

        croak qq{Bind filter "$fname" is not registered}

          unless exists $filters->{$fname};

    }

    # Default filter name not exists

    croak qq{Default bind filter "$default_filter" is not registered}

      if $default_filter && ! exists $filters->{$default_filter};

    # Column name not exists

    foreach my $column (keys %$filter) {

        croak qq{Column name "$column" in bind filter is not found in paramters}

          unless exists $params->{$column};

    }

}

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";

    }

}

1;

=head1 NAME

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

=head1 SYNOPSYS

Connect to the database.

    use DBIx::Custom;

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

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

Insert, update, and delete

    # Insert 

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

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

                 filter => {title => 'encode_utf8'});

    # Update 

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

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

                 where  => {id => 5},

                 filter => {title => 'encode_utf8'});

    # Update all

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

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

                     filter => {title => 'encode_utf8'});

    # Delete

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

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

                 filter => {title => 'encode_utf8'});

    # Delete all

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

Select

    # Select

    my $result = $dbi->select(table => 'books');

    # Select, more complex

    my $result = $dbi->select(

        table  => 'books',

        column => [qw/author title/],

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

        append => 'order by id limit 5',

        filter => {title => 'encode_utf8'}

    );

    # Select, join table

    my $result = $dbi->select(

        table    => ['books', 'rental'],

        column   => ['books.name as book_name']

        relation => {'books.id' => 'rental.book_id'}

    );

    # Select, more flexible where

    my $result = $dbi->select(

        table  => 'books',

        where  => ['{= author} and {like title}', 

                   {author => 'Ken', title => '%Perl%'}]

    );

Execute SQL

    # Execute SQL

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

    # Execute SQL with hash binding and filtering

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

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

                  filter => {title => 'encode_utf8'});

    # Create query and execute it

    my $query = $dbi->create_query(

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

    );

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

Other features.

    # Default filter

    $dbi->default_bind_filter('encode_utf8');

    $dbi->default_fetch_filter('decode_utf8');

    # Get DBI object

    my $dbh = $dbi->dbh;

Fetch row.

    # Fetch

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

        # ...

    }

    # Fetch hash

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

    }

=head1 DESCRIPTIONS

=head2 1. Features

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<select()>, 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>.

=head2 2. Connect to the database

C<connect()> method create a new L<DBIx::Custom>

object and connect to the database.

    use DBIx::Custom;

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

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

If database is SQLite, use L<DBIx::Custom::SQLite> instead.

you connect database easily.

    use DBIx::Custom::SQLite;

    my $dbi = DBIx::Custom::SQLite->connect(database => 'dbname');

If database is  MySQL, use L<DBIx::Custom::MySQL>.

    use DBIx::Custom::MySQL;

    my $dbi = DBIx::Custom::MySQL->connect(

        database => 'dbname',

        user     => 'ken',

        password => '!LFKD%$&'

    );

=head2 3. Suger methods

L<DBIx::Custom> has suger methods, such as C<insert()>, C<update()>,

C<delete()> or C<select()>. If you want to do small works,

You don't have to create SQL statements.

=head3 insert()

Execute insert statement.

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

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

The following SQL is executed.

    insert into (title, author) values (?, ?);

The values of C<title> and C<author> is embedded into the placeholders.

C<append> and C<filter> argument can be specified.

See also "METHODS" section.

=head3 update()

Execute update statement.

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

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

                 where  => {id => 5});

The following SQL is executed.

    update books set title = ?, author = ?;

The values of C<title> and C<author> is embedded into the placeholders.

C<append> and C<filter> argument can be specified.

See also "METHOD" section.

If you want to update all rows, use C<update_all()> method.

=head3 delete()

Execute delete statement.

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

                 where  => {author => 'Ken'});

The following SQL is executed.

    delete from books where id = ?;

The value of C<id> is embedded into the placehodler.

C<append> and C<filter> argument can be specified.

see also "METHODS" section.

If you want to delete all rows, use C<delete_all()> method.

=head3 select()

Execute select statement, only C<table> argument specified :

    my $result = $dbi->select(table => 'books');

The following SQL is executed.

    select * from books;

the result of C<select()> method is L<DBIx::Custom::Result> object.

You can fetch a row by C<fetch()> method.

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

        my $title  = $row->[0];

        my $author = $row->[1];

    }

L<DBIx::Custom::Result> has various methods to fetch row.

See "4. Fetch row".

C<column> and C<where> arguments specified.

    my $result = $dbi->select(

        table  => 'books',

        column => [qw/author title/],

        where  => {author => 'Ken'}

    );

The following SQL is executed.

    select author, title from books where author = ?;

the value of C<author> is embdded into the placeholder.

If you want to join tables, specify C<relation> argument. 

    my $result = $dbi->select(

        table    => ['books', 'rental'],

        column   => ['books.name as book_name']

        relation => {'books.id' => 'rental.book_id'}

    );

The following SQL is executed.

    select books.name as book_name from books, rental

    where books.id = rental.book_id;

If you want to add some string to the end of SQL statement,

use C<append> argument.

    my $result = $dbi->select(

        table  => 'books',

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

        append => 'order by price limit 5',

    );

The following SQL is executed.

    select * books where author = ? order by price limit 5;

C<filter> argument can be specified.

see also "METHODS" section.

=head2 4. Fetch row

C<select()> method return L<DBIx::Custom::Result> object.

You can fetch row by various methods.

Note that in this section, array means array reference,

and hash meanse hash reference.

Fetch row into array.

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

        my $author = $row->[0];

        my $title  = $row->[1];

    }

Fetch only a first row into array.

    my $row = $result->fetch_first;

Fetch multiple rows into array of array.

    while (my $rows = $result->fetch_multi(5)) {

        my $first_author  = $rows->[0][0];

        my $first_title   = $rows->[0][1];

        my $second_author = $rows->[1][0];

        my $second_value  = $rows->[1][1];

    }

Fetch all rows into array of array.

    my $rows = $result->fetch_all;

Fetch row into hash.

    # Fetch a row into hash

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

        my $title  = $row->{title};

        my $author = $row->{author};

    }

Fetch only a first row into hash

    my $row = $result->fetch_hash_first;

Fetch multiple rows into array of hash

    while (my $rows = $result->fetch_hash_multi(5)) {

        my $first_title   = $rows->[0]{title};

        my $first_author  = $rows->[0]{author};

        my $second_title  = $rows->[1]{title};

        my $second_author = $rows->[1]{author};

    }

Fetch all rows into array of hash

    my $rows = $result->fetch_hash_all;

If you want to access statement handle of L<DBI>, use C<sth> attribute.

    my $sth = $result->sth;

=head2 5. Hash parameter binding

L<DBIx::Custom> provides hash parameter binding.

At frist, I show normal parameter binding.

    use DBI;

    my $dbh = DBI->connect(...);

    my $sth = $dbh->prepare(

        "select * from books where author = ? and title like ?;"

    );

    $sth->execute('Ken', '%Perl%');

This is very good way because database system can enable SQL caching,

and parameter is quoted automatically. this is secure.

L<DBIx::Custom> hash parameter binding system improve

normal parameter binding to use hash parameter.

    my $result = $dbi->execute(

        "select * from books where {= author} and {like title};"

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

    );

This is same as the normal way, execpt that the parameter is hash.

{= author} and {like title} is called C<tag>.

tag is expand to placeholder string internally.

    select * from books where {= author} and {like title}

      -> select * from books where author = ? and title like ?;

The following tags is available.

    [TAG]                       [REPLACED]

    {? NAME}               ->   ?

    {= NAME}               ->   NAME = ?

    {<> NAME}              ->   NAME <> ?

    {< NAME}               ->   NAME < ?

    {> NAME}               ->   NAME > ?

    {>= NAME}              ->   NAME >= ?

    {<= NAME}              ->   NAME <= ?

    {like NAME}            ->   NAME like ?

    {in NAME COUNT}        ->   NAME in [?, ?, ..]

    {insert_param NAME1 NAME2}   ->   (NAME1, NAME2) values (?, ?)

    {update_param NAME1 NAME2}   ->   set NAME1 = ?, NAME2 = ?

See also L<DBIx::Custom::QueryBuilder>.

C<{> and C<}> is reserved. If you use these charactors,

you must escape them using '\'. Note that '\' is

already perl escaped charactor, so you must write '\\'. 

    'select * from books \\{ something statement \\}'

=head2 6. Filtering

Usually, Perl string is kept as internal string.

If you want to save the string to database, You must encode the string.

Filtering system help you to convert a data to another data

when you save to the data and get the data form database.

If you want to register filter, use C<register_filter()> method.

    $dbi->register_filter(

        to_upper_case => sub {

            my $value = shift;

            return uc $value;

        }

    );

C<encode_utf8> and C<decode_utf8> filter is registerd by default.

You can specify these filters to C<filter> argument of C<execute()> method.

    my $result = $dbi->execute(

        "select * from books where {= author} and {like title};"

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

        filter => {author => 'to_upper_case, title => 'encode_utf8'}

    );

C<filter> argument can be specified to suger methods, such as

C<insert()>, C<update()>, C<update_all()>,

C<delete()>, C<delete_all()>, C<select()>.

    # insert(), having filter argument

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

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

                 filter => {title => 'encode_utf8'});

    # select(), having filter argument

    my $result = $dbi->select(

        table  => 'books',

        column => [qw/author title/],

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

        append => 'order by id limit 1',

        filter => {title => 'encode_utf8'}

    );

Filter works each parmeter, but you prepare default filter for all parameters.

    $dbi->default_bind_filter('encode_utf8');

C<filter()> argument overwrites this default filter.

    $dbi->default_bind_filter('encode_utf8');

    $dbi->insert(

        table  => 'books',

        param  => {title => 'Perl', author => 'Ken', price => 1000},

        filter => {author => 'to_upper_case', price => undef}

    );

This is same as the following example.

    $dbi->insert(

        table  => 'books',

        param  => {title => 'Perl', author => 'Ken', price => 1000},

        filter => {title => 'encode_uft8' author => 'to_upper_case'}

    );

You can also specify filter when the row is fetched. This is reverse of bind filter.

    my $result = $dbi->select(table => 'books');

    $result->filter({title => 'decode_utf8', author => 'to_upper_case'});

Filter works each column value, but you prepare a default filter

for all clumn value.

    $dbi->default_fetch_filter('decode_utf8');

C<filter()> method of L<DBIx::Custom::Result>

overwrites this default filter.

    $dbi->default_fetch_filter('decode_utf8');

    my $result = $dbi->select(

        table => 'books',

        columns => ['title', 'author', 'price']

    );

    $result->filter({author => 'to_upper_case', price => undef});

This is same as the following one.

    my $result = $dbi->select(

        table => 'books',

        columns => ['title', 'author', 'price']

    );

    $result->filter({title => 'decode_utf8', author => 'to_upper_case'});

Note that in fetch filter, column names must be lower case

even if the column name conatains upper case charactors.

This is requirment not to depend database systems.

=head2 7. Get high performance

=head3 Disable filter checking

Filter checking is executed by default.

This is done to check right filter name is specified,

but sometimes damage performance.

If you disable this filter checking,

Set C<filter_check> attribute to 0.

    $dbi->filter_check(0);

=head3 Use execute() method instead suger methods

If you execute insert statement by C<insert()> method,

you sometimes can't get required performance.

C<insert()> method is a little slow because SQL statement and statement handle

is created every time.

In that case, you can prepare a query by C<create_query()> method.

    my $query = $dbi->create_query(

        "insert into books {insert_param title author};"

    );

Return value of C<create_query()> is L<DBIx::Custom::Query> object.

This keep the information of SQL and column names.

    {

        sql     => 'insert into books (title, author) values (?, ?);',

        columns => ['title', 'author']

    }

Execute query repeatedly.

    my $inputs = [

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

        {title => 'Good days', author => 'Mike'}

    ];

    foreach my $input (@$inputs) {

        $dbi->execute($query, $input);

    }

This is faster than C<insert()> method.

=head3 caching

C<execute()> method caches the parsed result of the source of SQL.