DBD::TreeData

# NAME

DBD::TreeData - DBI driver for any abstract hash/array tree

# SYNOPSIS

        use DBI;
        use JSON::Any;
        use LWP::Simple;

        # Example JSON object
        my $json = get 'http://maps.googleapis.com/maps/api/geocode/json?address=1600+Pennsylvania+Ave+NW,+20500&region=us&language=en&sensor=false';
        my $obj = JSON::Any->jsonToObj($json);

        my $dbh = DBI->connect('dbi:TreeData:', '', '', {
           tree_table_name => 'geocode',
           tree_data       => $obj,
        });

        # Informational dump
        use Data::Dump;
        dd ($dbh->table_info->fetchall_arrayref);
        dd (map { [ @{$_}[2 .. 6] ] } @{
           $dbh->column_info('','','','')->fetchall_arrayref
        });

        # DBIC dump
        use DBIx::Class::Schema::Loader 'make_schema_at';
        make_schema_at(
           'My::Schema', {
              debug => 1,
              dump_directory  => './lib',
           },
           [ 'dbi:TreeData:geocode', '', '', { tree_data => $obj } ],
        );

# DESCRIPTION

DBD::TreeData provides a DBI driver to translate any sort of tree-based data set (encapsulated in a Perl object) into a flat set of tables, complete with real SQL functionality. This module utilizes DBD::AnyData to create the new tables, which uses SQL::Statement to support the SQL parsing. (Any caveats with those modules likely applies here.)

This module can be handy to translate JSON, XML, YAML, and many other tree formats to be used in class sets like DBIx::Class. Unlike DBD::AnyData, the format of the data doesn't have to be pre-flattened, and will be spread out into multiple tables.

Also, this driver fully supports all of the `*_info` methods, making it ideal to shove into modules like DBIx::Class::Schema::Loader. (The `table_info` and `column_info` filters use REs with begin/end bounds pre-set.)

# CONNECT ATTRIBUTES

## tree_data

The actual tree object. Of course, this attribute is required.

## tree_table_name

The name of the starting table. Not required, but recommended. If not specified, defaults to 'tree_data', or the value of the driver DSN string (after the `dbi:TreeData:` part).

## tree_debug

Boolean. Print debug information while translating the tree.

## tree_rename_tables

Hashref of table names. If you don't like the name of an auto-created table, you can rename them while the database is being built. Within the hashref, the keys/values are the old/new names, respectively.

# TRANSLATION BEHAVIOR

The tree translation into flat tables is done using a recursive descent algorithm. It starts with a check of the current node's reference type, which dictates how it interprets the children. The goal is to create a fully 4NF database from the tree.

Arrays are interpreted as a list of rows, and typically get rolled up into "group" tables. Hashes are interpreted as a list of column names and values. Non-references are considered values. Scalar refs and VStrings are de-referenced first. Other types of refs are processed as best as possible, but the driver will complain. (Code ref blocks are currently NOT executed and discarded.)

Nested arrays will create nested group tables with different suffixes, like `matrix`, `cube`, and `hypercube`. If it has to go beyond that (and you really shouldn't have structures like that), it'll start complaining (sarcastically).

In almost all cases, the table name is derived from a previous key. Table names also use Lingua::EN::Inflect::Phrase to create pluralized names. Primary IDs will have singular names with a `_id` suffix.

For example, this tree:

        address_components => [
           {
              long_name  => 1600,
              short_name => 1600,
              types      => [ "street_number" ]
           },
           {
              long_name  => "President's Park",
              short_name => "President's Park",
              types      => [ "establishment" ]
           },
           {
              long_name  => "Pennsylvania Avenue Northwest",
              short_name => "Pennsylvania Ave NW",
              types      => [ "route" ]
           },
           {
              long_name  => "Washington",
              short_name => "Washington",
              types      => [ "locality", "political" ]
           },
           ... etc ...,
        ],

Would create the following tables:

        <main_table>
           address_component_groups
              address_components
                 type_groups
                    types

In this case, `address_components` has most of the columns and data, but it also has a tie to an ID of `address_component_groups`.

Since `types` points to an array, it will have its own dedicated table. That table would have data like:

        type_id │ type
        ════════╪════════════════
              1 │ street_number
              2 │ establishment
              3 │ route
              4 │ locality
              5 │ political
            ... │ ...

Most of the `type_groups` table would be a 1:1 match. However, the last component entry has more than one value in the `types` array, so the `type_group_id` associated to that component would have multiple entries (4 & 5). Duplicate values are also tracked, so that IDs are reused.

# CAVEATS

## DBI / DBD::AnyData Conflict

As of the time of this writing, the latest version of DBI (1.623) and the latest version of DBD::AnyData (0.110) do not work together. Since TreeData relies on DBD::AnyData for table creation, you will need to downgrade to DBI 1.622 to use this driver, until a new version of DBD::AnyData comes out.

# AVAILABILITY

The project homepage is https://github.com/SineSwiper/DBD-TreeData/wiki.

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit http://www.perl.com/CPAN/ to find a CPAN site near you, or see https://metacpan.org/module/DBD::TreeData/.

# SUPPORT

## Internet Relay Chat

You can get live help by using IRC ( Internet Relay Chat ). If you don't know what IRC is, please read this excellent guide: http://en.wikipedia.org/wiki/Internet_Relay_Chat. Please be courteous and patient when talking to us, as we might be busy or sleeping! You can join those networks/channels and get help:

- irc.perl.org

  You can connect to the server at 'irc.perl.org' and join this channel: #dbi then talk to this person for help: SineSwiper.

## Bugs / Feature Requests

Please report any bugs or feature requests via https://github.com/SineSwiper/DBD-TreeData/issues.

# AUTHOR

Brendan Byrd <BBYRD@CPAN.org>

# COPYRIGHT AND LICENSE

This software is Copyright (c) 2013 by Brendan Byrd.

This is free software, licensed under:

      The Artistic License 2.0 (GPL Compatible)