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=item Sales_by_user

=item Sales_by_region

=item and so on...

=back

Moreover, you depend on the end users (or programmers) to actually *use*
these tables, instead of the base fact table.

And you know -- users will always query the base fact table, because it
is easier.

=head1 AGGREGATE NAVIGATOR

The solution to this problem is to make the aggregates invisible: we
will create an intermediate layer, above DBI, that will intercept each
query made against the base fact table, and rewrite it so it will use
the best aggregate table available.

For example:

    ----------------------------------------------------------
    User SQL...                 Becomes...
    ----------------------------------------------------------
    SELECT                      SELECT
        month,                      month,
        SUM(sales)                  SUM(sales)
    FROM                        FROM
        Sales                       Sales_by_month
    WHERE                       WHERE
        year=2010                   year=2010
    GROUP BY                    GROUP BY
        month                       month
    ----------------------------------------------------------
    SELECT                      SELECT
        brand,                      brand,
        SUM(sales)                  SUM(sales)
    FROM                        FROM
        Sales                       Sales_by_brand
    WHERE                       WHERE
        year=2010                   year=2010
    GROUP BY                    GROUP BY
        brand                       brand 
    ----------------------------------------------------------
    SELECT                      SELECT
        month,                      month,
        brand,                      brand,
        SUM(sales)                  SUM(sales)
    FROM                        FROM
        Sales                       Sales_by_brand_by_month
    WHERE                       WHERE
        year=2010                   year=2010
    GROUP BY                    GROUP BY
        month,                      month,
        brand                       brand 
    ----------------------------------------------------------

The aggregate navigator, which performs this transformation, will improve
the performance of the data warehouse transparently.

=head1 WARNING

THIS IS ALPHA SOFTWARE. It could drink your beer and eat your hamster!

=head1 AUTHOR

Nelson Ferraz, C<< <nferraz at gmail.com> >>

=head1 BUGS

Please report any bugs or feature requests to C<bug-dw at rt.cpan.org>, or through
the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DataWarehouse>.  I will be notified, and then you'll
automatically be notified of progress on your bug as I make changes.

=head1 SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc DataWarehouse::Fact

You can also look for information at:

=over 4

=item * RT: CPAN's request tracker

L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=DataWarehouse>

=item * AnnoCPAN: Annotated CPAN documentation

L<http://annocpan.org/dist/DataWarehouse>

=item * CPAN Ratings

L<http://cpanratings.perl.org/d/DataWarehouse>

=item * Search CPAN

L<http://search.cpan.org/dist/DataWarehouse/>

=back


=head1 ACKNOWLEDGEMENTS


=head1 LICENSE AND COPYRIGHT

Copyright 2010 Nelson Ferraz.

This program is free software; you can redistribute it and/or modify it
under the terms of either: the GNU General Public License as published
by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.