Mark Lawrence

NAME

DBIx::ThinSQL::SQLite - add various functions to SQLite

VERSION

0.0.14 (2015-06-19) Development release.

SYNOPSIS

    use DBIx::ThinSQL;
    use DBIx::ThinSQL::SQLite
        qw/create_functions
           create_methods
           create_sqlite_sequence/;

    my $db = DBIx::ThinSQL->connect('dbi:SQLite:dbname=...');

    # Call once only to initialize permanently
    create_sqlite_sequence($db);

    # Call after every connect to the database
    create_functions( $db, qw/ debug create_sequence currval / );

    # Call once every program run
    create_methods(qw/create_sequence nextval/);

    # Then use SQL functions or Perl methods as required
    $db->do(q{ SELECT debug('logged via Log::Any->debug'); });
    $db->do(q{ SELECT create_sequence('name'); });
    $db->do(q{ SELECT nextval('name'); });
    $db->create_sequence('othername');
    $db->nextval('othername');

DESCRIPTION

DBIx::ThinSQL::SQLite adds various functions to the SQL syntax understood by SQLite, using the sqlite_create_function() and sqlite_create_aggregate_function() methods of DBD::SQLite. It also adds sequence methods to DBIx::ThinSQL database handles.

The following functions are exported on request:

create_sqlite_sequence( $dbh )

Ensure that the sqlite_sequence table exists. This function must be called on the database (once only - the changes are permanent) before any of the other sequence related functions or methods will work.

This function works by creating (and dropping) a table with an INTEGER PRIMARY KEY AUTOINCREMENT definition. If you are using the sequence support from this module you probably don't want to be creating your own tables with the autoincrement feature, as it may clash with this module.

create_functions( $dbh, @functions )

Add @functions to the SQL understood by SQLite for the database handle $dbh. @functions can be any combination of the following:

debug( @items )

This function called from SQL context logs @items with a debug() call to a Log::Any instance. If the first item of @items begins with /^select/i then that statement will be run and the result logged using log_debug from DBIx::ThinSQL instead.

warn( @items )

This function called from SQL context logs @items using Perl's warn function. If the first item of @items begins with /^select/i then that statement will be run using the current handle and the result warned instead.

create_sequence( $name )

Create a sequence in the database with name $name.

nextval( $name ) -> Int

Advance the sequence to its next value and return that value.

currval( $name ) -> Int

Return the current value of the sequence.

If Digest::SHA is installed then the following functions can also be created.

sha1( $expr, ... ) -> bytes

Calculate the SHA digest of $expr and return it in a 20-byte binary form. Unfortunately it seems that the underlying SQLite C sqlite_create_function() provides no way to identify the result as a blob, so you must always manually cast the result in SQL like so:

    CAST(sha1(SQLITE_EXPRESSION) AS blob)
sha1_hex( $expr, ... ) -> hexidecimal

Calculate the SQLite digest of $expr and return it in a 40-character hexidecimal form.

sha1_base64( $expr, ... ) -> base64

Calculate the SQLite digest of $expr and return it in a base64 encoded form.

agg_sha1( $expr, $sort_expr ) -> bytes
agg_sha1_hex( $expr, $sort_expr ) -> hexidecimal
agg_sha1_base64( $expr, $sort_expr ) -> base64

These aggregate functions are for use with statements using GROUP BY. $expr is the expression on which to calculate the SHA1 hash, and $sort_expr determines the (string) comparison order in which $expr is fed to the SHA1 stream.

Note that user-defined SQLite functions are only valid for the current session. They must be created each time you connect to the database. You can have this happen automatically at connect time by taking advantage of the DBI Callbacks attribute:

    my $db = DBI::ThinSQL->connect(
        $dsn, undef, undef,
        {
            Callbacks => {
                connected => sub {
                    my $dbh = shift;
                    create_functions( $dbh,
                        qw/debug nextval/ );
                  }
            },

        }
    );
create_methods( @methods )

Add @methods to the DBIx::ThinSQL::db class which can be any combination of the following:

create_sequence( $name )

Create a sequence in the database with name $name.

nextval( $name ) -> Int

Advance the sequence to its next value and return that value.

currval( $name ) -> Int

Return the current value of the sequence.

These methods are added to a Perl class and are therefore available to any DBIx::ThinSQL handle.

SEE ALSO

Log::Any

AUTHOR

Mark Lawrence <nomad@null.net>

COPYRIGHT AND LICENSE

Copyright (C) 2013-2014 Mark Lawrence <nomad@null.net>

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.