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עידו פרלמוטר (Ido Perlmuter)

NAME

MQUL - General purpose, MongoDB-style query and update language

SYNOPSIS

        use MQUL qw/doc_matches update_doc/;

        my $doc = {
                title => 'Freaks and Geeks',
                genres => [qw/comedy drama/],
                imdb_score => 9.4,
                seasons => 1,
                starring => ['Linda Cardellini', 'James Franco', 'Jason Segel'],
                likes => { up => 45, down => 11 }
        };

        if (doc_matches($doc, {
                title => qr/geeks/i,
                genres => 'comedy',
                imdb_score => { '$gte' => 5, '$lte' => 9.5 },
                starring => { '$type' => 'array', '$size' => 3 },
                'likes.up' => { '$gt' => 40 }
        })) {
                # will be true in this example
        }

        update_doc($doc, {
                '$set' => { title => 'Greeks and Feaks' },
                '$pop' => { genres => 1 },
                '$inc' => { imdb_score => 0.6 },
                '$unset' => { seasons => 1 },
                '$push' => { starring => 'John Francis Daley' },
        });

        # $doc will now be:
        {
                title => 'Greeks and Feaks',
                genres => ['comedy'],
                imdb_score => 10,
                starring => ['Linda Cardellini', 'James Franco', 'Jason Segel', 'John Francis Daley'],
                likes => { up => 45, down => 11 }
        }

DESCRIPTION

MQUL (for MongoDB-style Query & Update Language; pronounced "umm, cool"; yeah, I know, that's the dumbest thing ever), is a general purpose implementation of MongoDB's query and update language. The implementation is not 100% compatible, but it only slightly deviates from MongoDB's behavior, actually extending it a bit.

The module exports two subroutines: doc_matches() and update_doc(). The first subroutine takes a document, which is really just a hash-ref (of whatever complexity), and a query hash-ref built in the MQUL query language. It returns a true value if the document matches the query, and a false value otherwise. The second subroutine takes a document and an update hash-ref built in the MQUL update language. The subroutine modifies the document (in-place) according to the update hash-ref.

You can use this module for whatever purpose you see fit. It was actually written for Giddy, my Git-database, and was extracted from its original code. Outside of the database world, I plan to use it in an application that performs tests (such as process monitoring for example), and uses the query language to determine whether the results are valid or not (in our monitoring example, that could be CPU usage above a certain threshold and stuff like that). It is also used by MorboDB, an in-memory clone of MongoDB.

UPGRADE NOTES

My distributions follow the semantic versioning scheme, so whenever the major version changes, that means that API changes incompatible with previous versions have been made. Always read the Changes file before upgrading.

THE LANGUAGE

The language itself is described in MQUL::Reference. This document only describes the interface of this module.

The reference document also details MQUL's current differences from the original MongoDB language.

INTERFACE

doc_matches( \%document, [ \%query, \@defs ] )

Receives a document hash-ref and possibly a query hash-ref, and returns true if the document matches the query, false otherwise. If no query is given (or an empty hash-ref is given), true will be returned (every document will match an empty query - in accordance with MongoDB).

See "QUERY STRUCTURE" in MQUL::Reference to learn about the structure of query hash-refs.

Optionally, an even-numbered array reference of dynamically calculated attribute definitions can be provided. For example:

        [ min_val => { '$min' => ['attr1', 'attr2', 'attr3' ] },
          max_val => { '$max' => ['attr1', 'attr2', 'attr3' ] },
          difference => { '$diff' => ['max_val', 'min_val'] } ]

This defines three dynamic attributes: min_val, max_val and difference, which is made up of the first two.

See "DYNAMICALLY CALCULATED ATTRIBUTES" in MQUL::Reference for more information about dynamic attributes.

update_doc( \%document, \%update )

Receives a document hash-ref and an update hash-ref, and updates the document in-place according to the update hash-ref. Also returns the document after the update. If the update hash-ref doesn't have any of the update modifiers described by the language, then the update hash-ref is considered as what the document should now be, and so will simply replace the document hash-ref (once again, in accordance with MongoDB).

See "UPDATE STRUCTURE" in MQUL::Reference to learn about the structure of update hash-refs.

DIAGNOSTICS

MQUL::doc_matches() requires a document hash-ref.

This error means that you've either haven't passed the doc_matches() subroutine any parameters, or given it a non-hash-ref document.

MQUL::doc_matches() expects a query hash-ref.

This error means that you've passed the doc_matches() attribute a non-hash-ref query variable. While you don't actually have to pass a query variable, if you do, it has to be a hash-ref.

MQUL::update_doc() requires a document hash-ref.

This error means that you've either haven't passed the update_doc() subroutine any parameters, or given it a non-hash-ref document.

MQUL::update_doc() requires an update hash-ref.

This error means that you've passed the update_doc() subroutine a non-hash-ref update variable.

The %s attribute is not an array in the doc.

This error means that your update hash-ref tries to modify an array attribute (with $push, $pushAll, $addToSet, $pull, $pullAll, $pop, $shift and $splice), but the attribute in the document provided to the update_doc() subroutine is not an array.

CONFIGURATION AND ENVIRONMENT

MQUL requires no configuration files or environment variables.

DEPENDENCIES

MQUL depends on the following modules:

INCOMPATIBILITIES

None reported.

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests to bug-MQUL@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=MQUL.

AUTHOR

Ido Perlmuter <ido at ido50 dot net>

LICENSE AND COPYRIGHT

Copyright (c) 2011-2015, Ido Perlmuter ido at ido50 dot net.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either version 5.8.1 or any later version. See perlartistic and perlgpl.

The full text of the license can be found in the LICENSE file included with this module.

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.