NAME
    SHARYANTO::SQL::Schema - Routine and convention to create/update your
    application's DB schema

VERSION
    version 0.08

DESCRIPTION
    This module uses Log::Any for logging.

    To use this module, you typically run the create_or_update_db_schema()
    routine at the start of your program/script, e.g.:

     use DBI;
     use SHARYANTO::SQL::Schema qw(create_or_update_db_schema);
     my $spec = {...}; # the schema specification
     my $dbh = DBI->connect(...);
     my $res = create_or_update_db_schema(dbh=>$dbh, spec=>$spec);
     die "Cannot run the application: cannot create/upgrade database schema: $res->[1]"
         unless $res->[0] == 200;

    This way, your program automatically creates/updates database schema
    when run. Users need not know anything.

FAQ
  Why the name SHARYANTO::*?
    I haven't decided on a better name. See SHARYANTO.

  Why use this module instead of other similar solution?
    Mainly simplicity. I write simple application which is often
    self-contained in a single module/script. This module works with
    embedded SQL statements instead of having to put SQL in separate
    files/subdirectory.

  How do I see each SQL statement as it is being executed?
    Try using Log::Any::For::DBI, e.g.:

     % TRACE=1 perl -MLog::Any::For::DBI -MLog::Any::App yourapp.pl ...

TODO
    *   Configurable meta table name?

    *   Reversion/downgrade?

        Something which does not come up often yet in my case.

SEE ALSO
    Some other database migration tools that directly uses SQL:

    *   DBIx::Migration

        Pretty much similar to this module, with support for downgrades. OO
        style, SQL in separate files/subdirectory.

    *   Database::Migrator

        Pretty much similar. OO style, SQL in separate files/subdirectory.
        Perl scripts can also be executed for each version upgrade. Meta
        table is configurable (default recommended is 'AppliedMigrations').

    *   sqitch

        A more proper database change management tool with dependency
        resolution and VCS awareness. No numbering. Command-line script and
        Perl library provided. Looks pretty awesome and something which I
        hope to use for more complex applications.

AUTHOR
    Steven Haryanto <stevenharyanto@gmail.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2013 by Steven Haryanto.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

FUNCTIONS
    None are exported by default, but they are exportable.

  create_or_update_db_schema(%args) -> [status, msg, result, meta]
    Routine and convention to create/update your application's DB schema.

    With this routine (and some convention) you can easily create and update
    database schema for your application in a simple way using pure SQL.

    *Version*: version is an integer and starts from 1. Each software
    release with schema change will bump the version number by 1. Version
    information is stored in a special table called "meta" (SELECT value
    FROM meta WHERE name='schema_version').

    You supply the SQL statements in "spec". "spec" is a hash which contains
    the key "install" (the value of which is a series of SQL statements to
    create the schema from nothing). It should be the SQL statements to
    create the latest version of the schema.

    There should also be zero or more "upgrade_to_v$VERSION" keys, the value
    of each is a series of SQL statements to upgrade from ($VERSION-1) to
    $VERSION. So there could be "upgrade_to_v2", "upgrade_to_v3", and so on
    up the latest version.

    This routine will check the existence of the "meta" table and the
    current schema version. If "meta" table does not exist yet, the SQL
    statements in "install" will be executed. The "meta" table will also be
    created and a row ('schema_version', 1) is added.

    If "meta" table already exists, schema version will be read from it and
    one or more series of SQL statements from "upgrade_to_v$VERSION" will be
    executed to bring the schema to the latest version.

    Currently only tested on MySQL, Postgres, and SQLite. Postgres is
    recommended because it can do transactional DDL (a failed upgrade in the
    middle will not cause the database schema state to be inconsistent, e.g.
    in-between two versions).

    Arguments ('*' denotes required arguments):

    *   dbh* => *obj*

        DBI database handle.

    *   spec* => *hash*

        SQL statements to create and update schema.

        Example:

            {
                install => [
                    'CREATE TABLE IF NOT EXISTS t1 (...)',
                    'CREATE TABLE IF NOT EXISTS t2 (...)',
                ],
    
                upgrade_to_v2 => [
                    'ALTER TABLE t1 ADD COLUMN c5 INT NOT NULL',
                    'CREATE UNIQUE INDEX i1 ON t2(c1)',
                ],
    
                upgrade_to_v3 => [
                    'ALTER TABLE t2 DROP COLUMN c2',
                ],
            }

    Return value:

    Returns an enveloped result (an array). First element (status) is an
    integer containing HTTP status code (200 means OK, 4xx caller error, 5xx
    function error). Second element (msg) is a string containing error
    message, or 'OK' if status is 200. Third element (result) is optional,
    the actual result. Fourth element (meta) is called result metadata and
    is optional, a hash that contains extra information.

