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MLDBM::TinyDB - create and mainpulate structured MLDBM tied hash references 

=head1 SYNOPSIS

	use MLDBM::TinyDB;
	## or
	use MLDBM::TinyDB qw/db add_common/;

	@common = qw/created updated/; ## optional

	$tree = [TABLE, FIELDS_LIST,
			[TABLE1, FIELDS_LIST1,
				[TABLE2, FIELDS_LIST2],
				...
			],
			...
		]; 

	MLDBM::TinyDB::add_common($tree,\@common); ## optional
	## or
	add_common($tree,\@common);

	%obj = ();
	$obj{TABLE} = MLDBM::TinyDB->init(TABLE, $tree);
	## or
	$obj{TABLE} = 
		MLDBM::TinyDB->init(TABLE, $tree, undef, $mode, $perms);
	## or 
	$obj{TABLE} = MLDBM::TinyDB->init(TABLE); ## NEVER FIRST TIME

	@down = $obj{TABLE}->down; ## TABLE1

	$obj{TABLE1} = MLDBM::TinyDB::db(TABLE1);
	## or
	$obj{TABLE1} = db(TABLE1);

	$table = $obj{TABLE}->table; ## TABLE

	@down = $obj{TABLE1}->down; ## TABLE2

	$obj{TABLE2} = MLDBM::TinyDB::db(TABLE2);
	## or
	$obj{TABLE2} = db(TABLE2);

	@set_recs_indices = 
		$obj{TABLEn}->set_recs(ARRAYREF_TO_HASHREF,[LIST]);

	$up = $obj{TABLE2}->up; ## TABLE1
	
	$aref_of_href = $obj{TABLE}->get_ext_recs; 
	## or
	($aref_of_href, @get_recs_indices) = $obj{TABLE}->get_ext_recs;

	$aref_of_href1 = $obj{TABLE}->get_recs; ## NOT THE SAME AS ABOVE
	## or
	($aref_of_href1, @get_recs_indices1) =  $obj{TABLE}->get_recs;

	@indices_of_recs_found = $obj{TABLE}->search($criteria, [$limit]);
	@indices_of_recs_found = $obj{TABLE}->lsearch($criteria, [$limit]);
	
	@indices_and_sort_field_values = $obj{TABLE}->sort($sort_formula_string);
	@indices_and_sort_field_values = $obj{TABLE}->lsort($sort_formula_string);
	
	$obj{TABLEn}->delete([LIST]); 
	$obj{TABLEn}->last;


=head1 DESCRIPTION

MLDBM::TinyDB is MLDBM based module. It allows to create/manipulate data structure 
of related tables = more-then-flatfile-database. The main idea is to create array 
reference which will reflect database structure. The first scalar value in the array 
is table name, next ones are fields names - if the array contains array reference 
it denotes interior (related) table where first scalar value is that table name 
(in that case the record will contain the field of the same name as interior table) 
and the next ones are fields names and so on... If database structure isn't written on disk 
then that structure is fetched from the array reference and written to disk. 
Object is always built from disk structures. To define record you may use any field 
name except "nodes" which is restricted field name and shouldn't be specified 
explicitly. C<created> and C<updated> fields are handled 
internally - if they are specified then: 1)on I<append record> operation C<time> 
function value is set to C<created> record field 2)on I<write to existing record> 
operation C<time> function value is set to C<updated> record field. Data I<get from> 
and I<set to> records are in form of I<array reference to hash references> where hash 
keys are fields names. The fields names that are interior tables names contain array 
references. That array store indices (similar to array indices) identifying particular 
records. Those fields MUST be set to proper values before write records C<set_recs> operation. 

=head2 UTILITY

=over 4

=item MLDBM::TinyDB::add_common

=item add_common

Utility sub - allow to arbitrary fields names set (except C<nodes>) i.e. 
C<created, updated, blahblah> to be added just after first element (name of table) to all 
(sub-)arrays pointed by C<$tree> data structure. It's not exported by deafult. 

=back
 
=head2 CONSTRUCTOR(S) 

=over 4

=item init

This method creates database structure according to passed array reference C<$tree> 
(which defines hierarchical structure of related tables) if the structure doesn't exist 
on disk - in that case you may change default mode C<O_CREAT|O_RDWR> or perms C<0666> 
if you specify them. Afterwards C<init> read these structures and builds object from them.

=item MLDBM::TinyDB::db

=item db

Returns object reference of interior TABLE. If underlying database structure
doesn't exist on disk then it's created. Returns C<undef> on failure. Must be invoked 
after C<init>. It's not exported by default. 

=back

lib/MLDBM/TinyDB.pm  view on Meta::CPAN

Returns array of all fields names of record on which operate object.

=item last

Returns last record's index or -1 if there are no records.

=item down

Returns fields names that are also interior tables names or empty array otherwise.

=item up

Returns field name of superior table or C<undef> otherwise.

=item set_recs

Takes as first argument array reference to hash references and writes it as data records 
according to indices list if supplied or at the end of table otherwise. 
Each array element represents record data. If LIST is supplied then method 
writes at most as much array elements as LIST counts. If LIST is NOT supplied 
then it writes all array elements. May cause autovivification effect 
- it will add records if there is a gap between last record's index (see:C<last>) 
and supplied index of unexisted record. i.e. while last index (1) if supplied (3) 
then it will add (2, 3) records. Returns array of written records indices.

=item get_ext_recs

Gets record's data specified by indices list (or all records if list is not supplied)
and returns array reference to hash references plus got records indices list. If record 
field name is the same as interior table name then corresponding hash value will contain 
array reference - first element of the array will be other array reference to hash 
refrences (if one of that hash keys contain name of interior table then that hash 
value will be appropriate array reference and so on) and the rest of elements will be 
list of corresponding external records indices.

=item get_recs

Gets data records specified by indices list or all records if list is not supplied and 
returns array reference to hash references plus got records indices list. If any 
record field name is the same as interior table then corresponding hash value will contain 
array reference - the array will contain external records indices.

=item search

=item lsearch

Searches records in table in order to find ones that match supplied criteria,
returns array of indices of those records. The criteria is a string which may contain something like i.e. 
C<< field_name  > 1000 && (field_name1 =~ /PATTERN/ || field_name2 lt $string) >> or i.e.
C<defined(field_name)> meaning you can construct criteria string similar to
perl expressions. IMPORTANT: The use of fields names that are interior tables names  
(SEE: C<down> method) will take no effect. Second (optional) argument is $limit, 
which defines what number of record indices matching the criteria should be at most returned.
C<lsearch> differs from C<search> method in one way - it uses C<locale> pragma -
it uses system locale settings in string comparison/matching operations.

=item sort 

=item lsort

Sort the all records of table associated with object according to C<$sort_formula_string> which
must be specified. Returns array of array references, where each pointed array contains 
as first element index of record followed by sorted fields values in order they appear in 
C<$sort_formula_string>. Sort formula string is similar to perl sort function BLOCK 
i.e. C<< a(field_name) <=> b(field_name) >> - in this case C<field_name> value will be 
second element of each pointed array C<< a(field_name1) cmp b(field_name1)||length a(field_test2) <=> length b(field_test2) >>
- in this case C<field_name1> and C<field_name2> value will be second and third
element of each pointed array. If empty array is returned then something went wrong.
C<lsort> differs from C<sort> method in one way - it uses C<locale> pragma - it sorts
lexically in system locale sorting order.

=item delete

Deletes records of specified indices or all records if no arguments. If for record to
be deleted exists field C<nodes> and it contains array of numeric values then those values 
are indices identifying particular external table records and data in these external records 
pointing to that deleting record will be deleted too. 
 
=item table 

Returns TABLE associated with object.

=item name

Sets/gets name of object.

=head1 EXAMPLE1

	## DEFINE
	perl -e"use MLDBM::TinyDB;$tree=[qw/f a b/];$it=MLDBM::TinyDB->init(q/f/,$tree);"
	## ADD
	perl -e"use MLDBM::TinyDB;$it=MLDBM::TinyDB->init(q/f/);$it->set_recs([{a=>11,b=>12},{a=>12,b=>13}]);"
	## GET
	perl -e"use MLDBM::TinyDB;$it=MLDBM::TinyDB->init(q/f/);$g=$it->get_recs;for(@$g){print qq/@{[%$_]}\n/}"

=head1 EXAMPLE2

	use MLDBM::TinyDB qw/db add_common/;

	@common = qw/created updated/; ## option

	$tree = [qw/table1 field1/,
			[qw/table2 field2/,[qw/table3 field31 field32/]]
		]; 

	add_common($tree,\@common); ## option

	%obj = ();
	$obj{table1} = MLDBM::TinyDB->init("table1", $tree);
	$obj{table2} = db("table2");
	$obj{table3} = db("table3");

	@x = qw/green blue yellow black red/;
	@y = (1, undef, 3, 5, 2);
	for(my $i = 0; $i<@x; $i++) {
		my $href;
		$href->{field31} = $x[$i];
		$href->{field32} = $y[$i];
		push(@$aref, $href);
	}

	## NOTE: order of follownig statements is crucial to set all information 
	## needed about relations between these records