NAME¶
Tangram - Store pure objects in standard relational databases
SYNOPSIS¶
See Tangram::Tour
DESCRIPTION¶
Tangram is an
object-relational mapper. It is
orthogonal, meaning
that it does not require anything of the objects stored in it (other than the
common convention that base objects be based upon HASHes; individual columns
can be anything).
It consists of a
schema language that can describe or be built around an
object structure, or so as to closely match an existing SQL schema (with some
limitations). This schema language is rich enough to express such common RDBMS
features as links, foreign keys, and link tables.
It also consists of a
relational database storage engine, which based on
the schema structure, will make Perl structures persist in a relational (SQL
compliant) database. References to other objects (or collections, as
represented with foreign keys and link tables) may be loaded using
on
demand references that `lazily' load data when it is needed.
As of Tangram 2.08, the schema need not describe every single object property,
so that you can map only the columns you intend to query. The rest of the
object is then stored in a column via a serialiser, like Data::Dumper, YAML or
Storable. These structures themselves may contain arbitrary references to
other objects in storage.
Tangram has soundly engineered transaction support, without sacrificing
excellent data caching abilities. The general optimisation strategy of the
code makes it most suited for OLTP (aka application servers) and other
situations where it is better to select and update whole rows than to worry
about which columns to retrieve/update or not retrieve/update.
Once your object are persistent, you can build query expressions to find them in
terms of the schema language that you used to put them in. Therefore, the
schema data structure does not describe a data structure, it describes a
data access pattern.
If you are not picky about which accessor module to use, preferring to specify
the schema once only, then you can use the seperately distributed
Class::Tangram::Generator to make a set of classes from a Tangram schema
structure.
If you are looking for a tool that implements
SQL abstraction only, you
have probably missed the point (of this module, anyway), and a well-supported
module like Class::DBI, or an interactive SQL modeller like Alzabo will likely
suit your needs better.
Tangram is beginning to include preliminary support for aggregation functions,
and currently supports grouping, summing and counting. Joins must currently be
in terms of integer primary key columns, to extend past this would require
extra mapping types to be developed. Basic support for alternative join types
is present, but in its infancy.
Tangram currently contains no support for database-side updates (ie,
"UPDATE foo SET bar = 'baz' where frop = 'blarg'"), but support is
planned.
There is no support for creating views based on existing classes to make new
derived classes; you have to use your database SQL and create corresponding
Tangram classes manually to do that.
Tangram has a web site at <
http://tangram.utsl.gen.nz/>, currently
sponsored by MarketView (New Zealand) Ltd.
DOCUMENTATION INDEX¶
CONTENTS¶
- Tangram::Tour
- The original "Guided Tour" of the features of
Tangram, by Jean-Louis LeRoy.
- Tangram::Intro
- The humble beginnings of a new guided tour, based on the
next-generation features found in Tangram 2.08.
- Tangram::Springfield
- The classes and schema used in the Guided Tour(s).
- Tangram::Storage
- The main database handle class. Includes details on query
syntax.
- Tangram::Cursor
- Return an iterator that retrieves persistent objects in a
result set one by one.
- Tangram::Schema
- The Tangram schema structure - representing your data model
so that Tangram can map it.
- Tangram::Relational::Mappings
- An informative text on exactly how Object Relational
Mapping is accomplished by the Tangram::Relational back-end, what the
different styles of mapping are, and how each is selected.
- Tangram::Type
- What Tangram types are available. This page is an index of
other manual pages that express the data and relationship types available
in Tangram.
- Tangram::Type::Extending
- How to write your own custom types for Tangram.
- Tangram::Dialect
- Database-specific extensions to Tangram, such as
Tangram::mysql and Tangram::Sybase. These extensions only add
functionality, and are not required for core operation of Tangram.
COMPATIBILITY¶
Tangram has been known to run in the following environments, however, Tangram
uses standard SQL and should be usable with any SQL-83 compliant database.
Most of the requirements are simply avoiding the worst bugs.
Note that some functions (e.g. transactions and subselects) may not be available
in some environments. This is reported during the test suite.
- *
- Perl 5.005_03+, 5.6.1+, 5.8.1+ (5.8.0 had a nasty bug and
doesn't work with Tangram)
- *
- Set::Object 1.04 (though the latest version is highly
recommended)
- *
- DBI 1.14
- *
- DBD::mysql 2.0402
- *
- DBD::Oracle 1.06
- *
- DBD::Sybase 0.21
- *
- DBD::SQLite 1.07
- *
- DBD::Pg 0.93
LICENSE & WARRANTY¶
You may use Tangram, free of charge, under the terms of the GPL. This notice
applies to the entire distribution and all of its parts.
You can obtain a commercial license for old (2.04 and earlier) versions of
Tangram from Sound Object Logic, see
http://www.soundobjectlogic.com/tangram/licenses.html.
TANGRAM COMES WITHOUT ANY WARRANTY OF ANY KIND. IT DOES NOT EVEN COME WITH ANY
KIND OF VAGUE IMPLICATION THAT IT DOES ANYTHING MORE THAN GIVE YOUR COMPUTER
HINTS ABOUT HOW TO TRY STIRRING ITS ELECTRONS. THE AUTHORS ARE NOT RESPONSIBLE
FOR THE RESULTANT ELECTRON CONFIGURATION IN ANY WAY INCLUDING TRANSMUTATIONS
OF ELECTRONS INTO OTHER FIELDS SUCH AS MAGNETIC MEDIA OR PUNCH CARDS.
SUPPORT¶
Please send bug reports directly to the Tangram 2 maintainer's mailing list
<t2-users@lists.utsl.gen.nz>, and please CC:
<bug-Tangram@rt.cpan.org> so your fault can be tracked accurately.
Whenever possible, include a short yet complete script demonstrating the
problem. (read: if you want it fixed quicker, demonstrate it)
Questions of general interest should should be posted to the mailing list, but
not sent to rt.cpan.org.
AUTHORS¶
All the code and documentation for versions 2.04 and earlier, as well as some
changes in the 2.05 release, were written by Jean-Louis Leroy
(jll@soundobjectlogic.com) and Sound Object Logic.
Sam Vilain <sam@vilain.net> is the author of the derived work that is
Tangram 2.05 and later.
Andres Kievsky <ank@cpan.org> has contributed to the Tangram code starting
with Tangram 2.08.