NAME

DBIx::Recordset::Cookbook - working sample usages of DBIx::Recordset

INTRODUCTION

This document serves several purposes. One, it makes it easy to get started with DBIx::Recordset. Two, it serves as a place for those experienced with recordset to examine the code to discover how to make usage of recordset even simpler. Finally, it serves as a place for me to clarify all the areas in the original docs that were a bit confusing to me.

By working the examples in the order given in this document, you will be able to create a database and manipulate it, all from DBIx::Recordset.

Let the games begin!

CREATE THE DATABASE

Our Generic Connection Script:

#
#   scripts/dbconn.pl
#

use Data::Dumper;
use DBIx::Recordset;

sub dbh {
    *DBIx::Recordset::LOG   = \*STDOUT;
    $DBIx::Recordset::Debug = 2;

#my  $dsn = 'DBI:mysqlPP:database_name=test;host=localhost';
#    my  $dsn = 'DBI:mysqlPP:database=test;host=localhost';
    my  $dsn = 'DBI:mysql:database=test;host=localhost';
    our $dbh;

  my $attr = { RaiseError => 1 };
  my ($user, $pass);

  $dbh = DBI->connect($dsn, $user, $pass, $attr) or die $DBI::errstr;

}

sub conn_dbh {
    ( '!DataSource' => dbh() );
}

sub person_table {
    ( '!Table'      => 'person' );
}



1;

And Now the Script to Create the Tables:

#
#   scripts/create-tables.pl
#

require 'dbconn.pl';
use DBI;

my $person_tbl =<<EOSQL;
CREATE TABLE IF NOT EXISTS person (
id          mediumint unsigned not null primary key auto_increment,
name        varchar(40) not null,
age         varchar(255) not null,
country_id  mediumint unsigned
)
EOSQL

my $country_tbl =<<EOSQL;
CREATE TABLE IF NOT EXISTS country (
id          mediumint unsigned not null primary key auto_increment,
name        varchar(40) not null
)
EOSQL


my $dbh = dbh();


$dbh->do('use test');
$dbh->do($person_tbl);
$dbh->do($country_tbl);

POPULATE THE DATABASE

#
#   scripts/populate-person.pl
#

require 'dbconn.pl';
use DBI;

use Data::Dumper;


my @data = (
	    [qw(bill   25 ru)],
	    [qw(bob    30 de)],
	    [qw(bob    30 ca)],
	    [qw(bob    30 nz)],
	    [qw(jane   18 us)],
	    [qw(jane   48 dk)],
	    [qw(jane   22 nw)],
	    [qw(lazlo  40 hu)],
	    [qw(tony   40 uk)],
	    [qw(tony   21 yg)],
	    [qw(tony   22 ie)]
	    );

### no insert whole array ref huh?

for (@data) {

    my %h = (
	     name      => $_->[0],
	     age       => $_->[1],
	     country   => $_->[2]
	     );

    warn Dumper(\%h);

  DBIx::Recordset -> Insert ({%h,
			      ('!DataSource'   =>  dbh(),
			       '!Table'        =>  'person')});
}

SYNOPSIS

Selecting data with where criteria in a hash (formdata? :))

#
#   scripts/select-using-hash.pl
#

require 'dbconn.pl';
use DBIx::Recordset;

use vars qw(*rs);

*rs =
  DBIx::Recordset -> Search ({

      name => 'bob',
      age  => 30,
      conn_dbh(), person_table()

      });

#print Dumper(\@rs); # results not fetched --- you get nothing!
print Dumper($rs[0]{name});

Selecting data where values are in an arrayref:

#
#   scripts/select-using-aref.pl
#

require 'dbconn.pl';
use DBIx::Recordset;

use vars qw(*rs);

*rs =
  DBIx::Recordset -> Search ({

      '$where'   => 'name = ? and age = ?',
      '$values'  => ['bob',  30],
      conn_dbh(), person_table()

      });

#print Dumper(\@rs); # results not fetched --- you get nothing!
print Dumper($rs[0]{name});

Using Manual Indexing

#
#   scripts/synopsis-manual-indexing.pl
#

require 'dbconn.pl';
use DBIx::Recordset;
use strict;
use vars qw(*set);

my %where = (name => 'jane');

*set =
  DBIx::Recordset -> Search ({

      %where,
      conn_dbh(), person_table()

      });


print "A1: ", $set[0]{age}, $/;
print "A2: ", $set[1]{age}, $/;

# now to use the hash of the current record:

print "N: ", $set{name}, $/;
print "A: ", $set{age}, $/;

Reusing a Set Object to do Another Search:

#
#   scripts/do-another-search.pl
#

require 'dbconn.pl';
use DBIx::Recordset;

use vars qw(*set);

*set =
  DBIx::Recordset -> Search ({

      '$where'   => 'name = ? and age = ?',
      '$values'  => ['bob',  30],
      conn_dbh(), person_table()

      });


print $set[0]{name}, $/;
print $set[1]{name}, $/;

$set->Search({
    name => 'lazlo'
    });

print $set[0]{age}, $/;

Using Next() to Iterate over a Result Set:

#
#   scripts/all-users-with.pl
#

require 'dbconn.pl';
use DBIx::Recordset;
use strict;
use vars qw(*set);

my %where = (name => 'tony');

*set =
  DBIx::Recordset -> Search ({

      %where,
      conn_dbh(), person_table()

      });


while (my $rec = $set->Next) {
    print $rec->{age}, $/;
}

Using Next() but Using the Implicitly Bound Hash:

#
#   scripts/using-hash-of-recordset.pl
#

require 'dbconn.pl';
use Data::Dumper;
use DBIx::Recordset;

use vars qw(*set);

*set =
  DBIx::Recordset -> Search ({

      name => 'jane',
      conn_dbh(), person_table()

      });


while ($set->Next) {
    print Dumper(\%set);
}

DBIx::Recordset is a perl module for abstraction and simplification of database access.

The goal is to make standard database access (select/insert/update/delete) easier to handle and independent of the underlying DBMS. While special attention is paid to web applications, making it possible to handle state-less access and process the posted data of formfields, DBIx::Recordset is not limited to such applications.

DBIx::Recordset uses the DBI API to access the database, so it should work with every database for which a DBD driver is available (see also DBIx::Compat).

Most public functions take a hash reference as parameter, which makes it simple to supply various different arguments to the same function. The parameter hash can also be taken from a hash containing posted formfields like those available with CGI.pm, mod_perl, HTML::Embperl and others.

Before using a recordset it is necessary to setup an object. Of course the setup step can be made with the same function call as the first database access, but it can also be handled separately.

Most functions which set up an object return a typeglob. A typeglob in Perl is an object which holds pointers to all datatypes with the same name. Therefore a typeglob must always have a name and can't be declared with my. You can only use it as global (package) variable or declare it with local. The trick for using a typglob is that setup functions can return a reference to an object, an array and a hash at the same time.

... concerns about package variables and mod_perl ...

The object is used to access the object's methods, the array is used to access the records currently selected in the recordset and the hash is used to access the current record.

If you don't like the idea of using typglobs you can also set up the object, array and hash separately, or just set the ones you need.

ARGUMENTS

Since most methods take a hash reference as argument, here is a description of the valid arguments first.

Setup Parameters

All parameters starting with an '!' are only recognized at setup time. If you specify them in later function calls they will be ignored. Note: You can also preset these parameters with the TableAttr method of DBIx::Database. This allows you to setup most parameters for the whole database once and they will be use every time you create a new DBIx::Recordset object, without specifying it every time.

!DataSource

Specifies the database to which to connect. This information can be given in the following ways:

a DBI database handle

Uses a given database handle.

Driver/DB/Host.

Same as the first parameter to the DBI connect function.

DBIx::Recordset object

Takes the same database handle as the given DBIx::Recordset object.

DBIx::Database object

Takes Driver/DB/Host from the given database object. See DBIx::Database for details about DBIx::Database object. When using more than one Recordset object, this is the most efficient method.

DBIx::Database object name

Takes Driver/DB/Host from the database object which is saved under the given name ($saveas parameter to DBIx::Database -> new)

!Table

Tablename. Multiple tables are comma-separated.

!Username

Username. Same as the second parameter to the DBI connect function.

!Password

Password. Same as the third parameter to the DBI connect function.

!DBIAttr

Reference to a hash which holds the attributes for the DBI connect function. See perldoc DBI for a detailed description.

!Fields

Fields which should be returned by a query. If you have specified multiple tables the fieldnames should be unique. If the names are not unique you must specify them along with the tablename (e.g. tab1.field).

NOTE 1: Fieldnames specified with !Fields can't be overridden. If you plan to use other fields with this object later, use $Fields instead.

NOTE 2: The keys for the returned hash normally don't have a table part. Only the fieldname part forms the key. (See !LongNames for an exception.)

NOTE 3: Because the query result is returned in a hash, there can only be one out of multiple fields with the same name fetched at once. If you specify multiple fields with the same name, only one is returned from a query. Which one this actually is depends on the DBD driver. (See !LongNames for an exception.)

NOTE 4: Some databases (e.g. mSQL) require you to always qualify a fieldname with a tablename if more than one table is accessed in one query.

!TableFilter

The TableFilter parameter specifies which tables should be honoured when DBIx::Recordset searches for links between tables (see below). When given as parameter to DBIx::Database it filters for which tables DBIx::Database retrieves metadata. Only thoses tables are used which starts with prefix given by !TableFilter. Also the DBIx::Recordset link detection tries to use this value as a prefix of table names, so you can leave out this prefix when you write a fieldname that should be detected as a link to another table.

!LongNames

When set to 1, the keys of the hash returned for each record not only consist of the fieldnames, but are built in the form table.field.

!Order

Fields which should be used for ordering any query. If you have specified multiple tables the fieldnames should be unique. If the names are not unique you must specify them among with the tablename (e.g. tab1.field).

NOTE 1: Fieldnames specified with !Order can't be overridden. If you plan to use other fields with this object later, use $order instead.

... of course the question being how to do ascending and descending

!TabRelation

Condition which describes the relation between the given tables (e.g. tab1.id = tab2.id) (See also !TabJoin.)

Example

'!Table'       => 'tab1, tab2',
'!TabRelation' => 'tab1.id=tab2.id',
'name'         => 'foo'

This will generate the following SQL statement:

SELECT * FROM tab1, tab2 WHERE name = 'foo' and tab1.id=tab2.id ;

!TabJoin

!TabJoin allows you to specify an INNER/RIGHT/LEFT JOIN which is used in a SELECT statement. (See also !TabRelation.)

Example

'!Table'   => 'tab1, tab2',
'!TabJoin' => 'tab1 LEFT JOIN tab2 ON	(tab1.id=tab2.id)',
'name'     => 'foo'

This will generate the following SQL statement:

SELECT * FROM tab1 LEFT JOIN tab2 ON	(tab1.id=tab2.id) WHERE name = 
'foo' ;

!PrimKey

Name of the primary key. When this key appears in a WHERE parameter list (see below), DBIx::Recordset will ignore all other keys in the list, speeding up WHERE expression preparation and execution.

... oh I think I see. He means that the primary key alone should be enough to find your records, so why bother with anything else. So, if you set this up beforehand, then when formdata came piling in, you could search on primary key only if it happened to be in the formdata.

Note that this key does NOT have to correspond to a field tagged as PRIMARY KEY in a CREATE TABLE statement.

!Serial

Name of the primary key. In contrast to !PrimKey this field is treated as an autoincrement field. If the database does not support autoincrement fields, but sequences the field is set to the next value of a sequence (see !Sequence and !SeqClass) upon each insert. If a !SeqClass is given the values are always retrived from the sequence class regardless if the DBMS supports autoincrement or not. The value from this field from the last insert could be retrieved by the function LastSerial.

... aha! an how-to! ...

!Sequence

Name of the sequence to use for this table when inserting a new record and !Serial is defind. Defaults to <tablename>_seq.

... a feature related to DBMS which use sequences

!SeqClass

Name and Parameter for a class that can generate unique sequence values. This is a string that holds comma separated values. The first value is the class name and the following parameters are given to the new constructor. See also DBIx::Recordset::FileSeq and DBIx::Recordset::DBSeq.

Example:

'!SeqClass' => 'DBIx::Recordset::FileSeq, /tmp/seq'

... another sequence-related feature

!WriteMode

!WriteMode specifies which write operations to the database are allowed and which are disabled. You may want to set !WriteMode to zero if you only need to query data, to avoid accidentally changing the content of the database.

NOTE: The !WriteMode only works for the DBIx::Recordset methods. If you disable !WriteMode, it is still possible to use do to send normal SQL statements to the database engine to write/delete any data.

!WriteMode consists of some flags, which may be added together:

DBIx::Recordset::wmNONE (0)

Allow no write access to the table(s)

DBIx::Recordset::wmINSERT (1)

Allow INSERT

DBIx::Recordset::wmUPDATE (2)

Allow UPDATE

DBIx::Recordset::wmDELETE (4)

Allow DELETE

DBIx::Recordset::wmCLEAR (8)

To allow DELETE for the whole table, wmDELETE must be also specified. This is necessary for assigning a hash to a hash which is tied to a table. (Perl will first erase the whole table, then insert the new data.)

DBIx::Recordset::wmALL (15)

Allow every access to the table(s)

Default is wmINSERT + wmUPDATE + wmDELETE

!StoreAll

If present, this will cause DBIx::Recordset to store all rows which will be fetched between consecutive accesses, so it's possible to access data in a random order. (e.g. row 5, 2, 7, 1 etc.) If not specified, rows will only be fetched into memory if requested, which means that you will have to access rows in ascending order. (e.g. 1,2,3 if you try 3,2,4 you will get an undef for row 2 while 3 and 4 is ok) see also DATA ACCESS below.

!HashAsRowKey

By default, the hash returned by the setup function is tied to the current record.

... this is already confusing. by "Setup Function" I presume he means the function SetupObject and only this function? Or does he mean any function which calls SetupObject. Such as Search(), Insert(), Update(), Delete().

Also, the hash is not "returned" because the last sentence below says that this whole discussion relates to functions which return a typeglob... therefore I think he means functions which bind a hash with data of the current record.>

You can use it to access the fields of the current record. If you set this parameter to true, the hash will by tied to the whole database. This means that the key of the hash will be used as the primary key in the table to select one row.

... cool can we get an example of this?

(This parameter only has an effect on functions which return a typglob.)

... "typglob" should be spelled "typeglob"

!IgnoreEmpty

This parameter defines how empty and undefined values are handled. The values 1 and 2 may be helpful when using DBIx::Recordset inside a CGI script, because browsers send empty formfields as empty strings.

0 (default)

An undefined value is treated as SQL NULL: an empty string remains an empty string.

1

All fields with an undefined value are ignored when building the WHERE expression.

2

All fields with an undefined value or an empty string are ignored when building the WHERE expression.

NOTE: The default for versions before 0.18 was 2.

!Filter

Filters can be used to pre/post-process the data which is read from/written to the database. The !Filter parameter takes a hash reference which contains the filter functions. If the key is numeric, it is treated as a type value and the filter is applied to all fields of that type. If the key if alphanumeric, the filter is applied to the named field. Every filter description consists of an array with at least two elements. The first element must contain the input function, and the second element must contain the output function. Either may be undef, if only one of them are necessary. The data is passed to the input function before it is written to the database. The input function must return the value in the correct format for the database. The output function is applied to data read from the database before it is returned to the user.

 Example:

     '!Filter'   => 
	{
	DBI::SQL_DATE     => 
	    [ 
		sub { shift =~ /(\d\d)\.(\d\d)\.(\d\d)/ ; "19$3$2$1"},
		sub { shift =~ /\d\d(\d\d)(\d\d)(\d\d)/ ; "$3.$2.$1"}
	    ],

	'datefield' =>
	    [ 
		sub { shift =~ /(\d\d)\.(\d\d)\.(\d\d)/ ; "19$3$2$1"},
		sub { shift =~ /\d\d(\d\d)(\d\d)(\d\d)/ ; "$3.$2.$1"}
	    ],

	}

Both filters convert a date in the format dd.mm.yy to the database format 19yymmdd and vice versa. The first one does this for all fields of the type SQL_DATE, the second one does this for the fields with the name datefield.

The !Filter parameter can also be passed to the function TableAttr of the DBIx::Database object. In this case it applies to all DBIx::Recordset objects which use these tables.

... aha! so this is the second place so far that we have a means of globally affecting all recordset object using tables. This means less needs be done in pure OOP and more can be done by Recordset, for better or worse

A third parameter can be optionally specified. It could be set to DBIx::Recordset::rqINSERT, DBIx::Recordset::rqUPDATE, or the sum of both. If set, the InputFunction (which is called during UPDATE or INSERT) is always called for this field in updates and/or inserts depending on the value.

... what InputFunction is he talking about?

If there is no data specified for this field as an argument to a function which causes an UPDATE/INSERT, the InputFunction is called with an argument of undef.

During UPDATE and INSERT the input function gets either the string 'insert' or 'update' passed as second parameter.

!LinkName

This allows you to get a clear text description of a linked table, instead of (or in addition to) the !LinkField. For example, if you have a record with all your bills, and each record contains a customer number, setting !LinkName DBIx::Recordset can automatically retrieve the name of the customer instead of (or in addition to) the bill record itself.

1 select additional fields

This will additionally select all fields given in !NameField of the Link or the table attributes (see TableAttr).

2 build name in uppercase of !MainField

This takes the values of !NameField of the Link or the table attributes (see TableAttr) and joins the content of these fields together into a new field, which has the same name as the !MainField, but in uppercase.

2 replace !MainField with the contents of !NameField

Same as 2, but the !MainField is replaced with "name" of the linked record.

See also !Links and WORKING WITH MULTIPLE TABLES below

!Links

This parameter can be used to link multiple tables together. It takes a reference to a hash, which has - as keys, names for a special "linkfield" and - as value, a parameter hash. The parameter hash can contain all the Setup parameters. The setup parameters are taken to construct a new recordset object to access the linked table. If !DataSource is omitted (as it normally should be), the same DataSource (and database handle), as the main object is taken. There are special parameters which can only occur in a link definition (see next paragraph). For a detailed description of how links are handled, see WORKING WITH MULTIPLE TABLES below.

Link Parameters

!MainField

The !MailField parameter holds a fieldname which is used to retrieve a key value for the search in the linked table from the main table. If omitted, it is set to the same value as !LinkedField.

!LinkedField

The fieldname which holds the key value in the linked table. If omitted, it is set to the same value as !MainField.

!NameField

This specifies the field or fields which will be used as a "name" for the destination table. It may be a string or a reference to an array of strings. For example, if you link to an address table, you may specify the field "nickname" as the name field for that table, or you may use ['name', 'street', 'city'].

Look at !LinkName for more information.

... this is very confusing... there is some stuff in test.pl in the Recorset distribution which does this... but boy is it confusing!

!DoOnConnect

You can give an SQL Statement (or an array reference of SQL statements), that will be executed every time, just after an connect to the db. As third possibilty you can give an hash reference. After every successful connect, DBIx::Recordset excutes the statements, in the element which corresponds to the name of the driver. '*' is executed for all drivers.

!Default

Specifies default values for new rows that are inserted via hash or array access. The Insert method ignores this parameter.

!TieRow

Setting this parameter to zero will cause DBIx::Recordset to not tie the returned rows to an DBIx::Recordset::Row object and instead returns an simple hash. The benefit of this is that it will speed up things, but you aren't able to write to such an row, nor can you use the link feature with such a row.

!Debug

Set the debug level. See DEBUGGING.

!PreFetch

Only for tieing a hash! Gives an where expression (either as string or as hashref) that is used to prefetch records from that database. All following accesses to the tied hash only access this prefetched data and don't execute any database queries. See !Expires how to force a refetch. Giving a '*' as value to !PreFetch fetches the whole table into memory.

The following example prefetches all record with id < 7:

tie %dbhash, 'DBIx::Recordset::Hash', {'!DataSource'   =>  $DSN,
                                       '!Username'     =>  $User,
                                       '!Password'     =>  $Password,
                                       '!Table'        =>  'foo',
                                       '!PreFetch'     =>  {
                                                            '*id' => '<',
                                                            'id' => 7
                                                           },
                                       '!PrimKey'      =>  'id'} ;

The following example prefetches all records:

tie %dbhash, 'DBIx::Recordset::Hash', {'!DataSource'   =>  $DSN,
                                       '!Username'     =>  $User,
                                       '!Password'     =>  $Password,
                                       '!Table'        =>  'bar',
                                       '!PreFetch'     =>  '*',
                                       '!PrimKey'      =>  'id'} ;

!Expires

Only for tieing a hash! If the values is numeric, the prefetched data will be refetched is it is older then the given number of seconds. If the values is a CODEREF the function is called and the data is refetched is the function returns true.

!MergeFunc

Only for tieing a hash! Gives an reference to an function that is called when more then one record for a given hash key is found to merge the records into one. The function receives a refence to both records a arguments. If more the two records are found, the function is called again for each following record, which is already merged data as first parameter.

The following example sets up a hash, that, when more then one record with the same id is
found, the field C<sum> is added and the first record is returned, where the C<sum> field
contains the sum of B<all> found records:

tie %dbhash, 'DBIx::Recordset::Hash', {'!DataSource'   =>  $DSN,
                                       '!Username'     =>  $User,
                                       '!Password'     =>  $Password,
                                       '!Table'        =>  'bar',
                                       '!MergeFunc'    =>  sub { my ($a, $b) = @_ ; $a->{sum} += $b->{sum} ; },
                                       '!PrimKey'      =>  'id'} ;

AUTHOR

T. M. Brannon, <tbone@cpan.org>

cpanm DBIx::Recordset::Cookbook

perl -MCPAN -e shell
install DBIx::Recordset::Cookbook