phpman > perldoc > SQL::Statement::Roadmap(3pm)

NAME
    SQL::Statement::Roadmap - Planned Enhancements for SQL::Statement and SQL::Parser

    Jens Rehsack - June 2010

SYNOPSIS
    This document gives a high level overview of the future of SQL::Statement, SQL::Parser and its
    impact.

    The planned enhancements cover testing, performance, reliability, extensibility and more.

CHANGES AND ENHANCEMENTS
  Enhancements in SQL::Statement 1.xx
    SQL::Statement 1.xx will not receive big changes, but a few enhancements may help us to design
    SQL::Statement 2.xx much better.

   CREATE and DROP of FUNCTION, KEYWORD, OPERATOR, TYPE
    SQL::Statement is missing some functions, types, operators etc. It's supported to add missing
    functionality - but the implementation was not picked up during the modernizing of column
    evaluation. See RT#52397 for some more information.

    This should be done before SQL::Statement 1.xx reaches the end of its road.

   Parser improvements
    The SQL::Parser is implemented based on a lot of regular expressions and some manually developed
    logic. This creates some issues like RT#53416 or RT#55190. Further, trailing ";" causes
    SQL::Parser to croak. We need to decide what can be fixed without internal design changes and
    what has to wait.

   Performance
    There is no intention to work on performance improvements in SQL::Statement 1.xx. The
    performance is good as it is and improvement requires design changes.

   Reliability
    Bugs will be fixed - where possible. SQL::Statement 1.28 is much more reliable than
    SQL::Statement 1.15. Even if a bug cannot be fixed all issues are gratefully received as they
    will be considered in the design process for SQL::Statement 2.xx better.

   Extensibility
    SQL::Statement 1.xx is highly extensible, even if a more object oriented design would improve
    that. The 1.xx branch will not be redesigned for greater extensibility on a coding level.

  Enhancements in SQL::Statement 2.xx
    Concerning the procedural design of SQL::Statement 1.xx a rewrite of the basic components is
    required.

   SQL::Parser rewrite
    The SQL::Parser needs to be modified to be able to use a Backus Naur Form
    <http://en.wikipedia.org/wiki/Backus_Naur_Form>. This would allow users and developers to rely
    on many different SQL dialects. This will allow better extensibility from a feature point of
    view without losing ANSI SQL compatibility.

   SQL::Statement rewrite
    SQL::Statement should be reduced to a simple coordinating engine. The executing tasks should be
    organized into separated commands. This will reduce side effects and will open the door for
    higher level optimizations, reliability improvements or sub-selects (or other calculated
    tables).

   Features
    There is a large list of missing features but not all table backends will be able to support
    each new feature. The most popular requested features need additional discussion and everyone is
    welcome to do it on the mailto:dbi-dev AT perl.org.

   LOCK TABLE
    Locking table within SQL scripts to manually control table consistence over several operations.
    The current locking support is restricted to one statement.

   Transaction support
    Executing statements on a temporary copy of the table data.

    The easiest way to implement this would be to create a SQL::Statement::RAM on "BEGIN
    TRANSACTION" and write the entire table back on "COMMIT" or discard on "ROLLBACK".

    Better performance could be achieved in cases where the implementation is enabled to memorize
    pending modifications and apply them at "COMMIT". On the other hand there are already
    capabilities to improve some operations, which might create confusion in case of transactions.

    This needs more discussion.

   ALTER TABLE
    Adding, removing or modifying columns is not supported for created tables. A generic "ALTER
    TABLE" seems to rely on the implementation of the transaction support - until better ideas are
    provided.

   Indices
    Currently some table backends have implicit support to access specified rows quicker than
    fetching each row and evaluating the where clause against the row data.

    An interface would be required to configure fetching to return only rows matching a restricted
    where clause. Another (probably better) way to support indices would be to fetch index entries
    at first and have an interface to the table fetching lines based on an index key.

   Sub-Selects
    In most cases queries can be re-expressed without using sub-selects. But in any case, there are
    circumstances where sub-selects are required.

    The first implementation will do the sub-select before the primary statement is executed without
    any further optimization. Hopefully a later version will provide better Performance with some
    optimization.

   Query based variables
    Currently the only variable I can imagine is "ROWNUM". More suggestions are very welcome.

   Better SQL Script support
    In SQL::Statement 1.xx the function "RUN ()" provides SQL script execution. This function may
    have limitations and side effects (at least when the executed SQL touched the same tables as the
    primary statement).

    I plan to improve the SQL script support to remove the side effects on the one hand and have a
    more flexible and easier way to execute them.

    Finally it should be possible to execute a script via:

        $dbh->do( join( ";", @script ) );

   Trigger support
    Most important when doing complicated things is having callback functions for several events.
    While real triggers will not be possible for SQL::Statement and underlying pseudo-databases,
    callbacks could be provided via triggers.

   Performance
    There are several performance optimizations required for SQL::Statement 2.xx.

    The first one should be done on a very high level (query optimization) by implementing algebraic
    evaluation of queries and clean implementation of typical database algorithms. With respect to
    the basic optimization rule *premature optimization is the root of all evil*, it is primarily
    targeted to have an adequately fast, reliable implementation of many algorithms (e.g. early
    incomplete evaluation to reduce amount of rows, transpose where clause to evaluate constants
    first) and a clever controller choosing the right algorithm for a specific query.

    The second optimization goal means: implementing most expensive methods in XS. This requires a
    good performance test suite as well as some real world usage cases.

   Reliability
    This is one of the primary goals of SQL::Statement. I hope to reach it using test driven
    development and I hope I get some more todo's from the users for this.

   Extensibility
    The currently high level of extensibility should be increased on a coding level. This will be
    done by redesigning the entire parser and execution engine using object oriented techniques and
    design patterns.

   Testing
    Many tests in SQL::Statement are not well organized. The tests should be reorganized into
    several parts:

    Basic API
        This part should test the entire basic API of SQL::Statement, SQL::Parser and probably the
        entire engine command classes.

    DBI / Table API
        This part should test if the API to DBI drivers work (maybe an empty test driver will be
        needed for that).

    Functionality
        This part should test the functionality of the SQL::Parser and the SQL::Statement engine.

    Performance
        This part should be used to implement full usage cases (ideally from real world projects) to
        allow for testing optimizations.

PRIORITIES
    Our priorities are localized to our current issues and proof of concept fixes for upcoming
    SQL::Statement 2.xx.

    Any additional priorities (as missing features, the SQL::Statement rewrite) will come later and
    can be modified by (paying) users.

RESOURCES AND CONTRIBUTIONS
    See <http://dbi.perl.org/contributing> for *how you can help*.

    If your company has benefited from the DBI or SQL::Statement, please consider if it could make a
    donation to The Perl Foundation "DBI Development" or "SQL::Statement Development" fund at
    <http://dbi.perl.org/donate> to secure future development.

    Alternatively, if your company would benefit from a specific new DBI or SQL::Statement feature,
    please consider sponsoring its development through the options listed in the section "Commercial
    Support from the Author" on <http://dbi.perl.org/support/>.

    Using such targeted financing allows you to contribute to DBI development (including
    SQL::Statement and PurePerl DBI drivers) and rapidly get something specific and directly
    valuable to you in return.

    Thank you.