Thilo Planz > DBIx-ProcedureCall-0.11 > DBIx::ProcedureCall

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NAME ^

DBIx::ProcedureCall - Perl extension to make database stored procedures look like Perl subroutines

SYNOPSIS ^

  use DBIx::ProcedureCall qw(sysdate);
  
  my $conn = DBI->connect(.....);
  
  print sysdate($conn);

DESCRIPTION ^

When developing applications for a database that supports stored procedures, it is a good idea to put all your database access code right into the database..

This module provides a convenient way to call stored procedures from Perl by creating wrapper subroutines that produce the necessary SQL statements, bind parameters and run the query.

While this module's interface is database-independent, only Oracle and PostgreSQL are currently supported.

EXPORT

DBIx::ProcedureCall exports subroutines for any stored procedures (and functions) that you ask it to. You specify the list of procedures that you want when using the module:

    use DBIx::ProcedureCall qw[ sysdate ]
    
    # gives you
    
    print sysdate($conn);

Calling such a subroutine will invoke the stored procedure. The subroutines expect a DBI database handle as their first parameter.

Subroutine names

The name of the subroutine is derived from the name of the stored procedure. Because the procedure name can contain characters that are not valid in a Perl procedure name, it will be sanitized a little:

Everything that is not a letter or a number becomes underscores. This will happen for all procedures that are part of a hierarchy ( such as an Oracle PL/SQL package or qualified with a schema), where the parts of the procedure name are divided by a dot.

        use DBIx::ProcedureCall qw( 
                sysdate
                dbms_random.random
                hh\$\$uu
                );
                
        # gives you
        
        sysdate();                                # no change
        dbms_random_random();    # note the underscore
        hh__uu();                           # dollar signs removed

You can request stored procedures that do not exist. This will not be detected by DBIx::ProcedureCall, but results in a database error when you try to call them.

Parameters

You can pass parameters to the subroutines You can use both positional and named parameters (if the database you are using supports them), but cannot mix the two styles in the same call.

Positional parameters are passed in after the database handle, which is always the first parameter:

        dbms_random_initialize($conn, 12345);

Named parameters are passed as a hash reference:

        dbms_random_initialize($conn, { val => 12345678 } );

The parameters you use have to match the parameters defined (in the database) for the stored procedure. If they do not, you will get a database error at runtime.

OUT and INOUT parameters

You can also use OUT and INOUT parameters, which return values from the stored procedure, by setting up a scalar variable to receive the result and passing a reference to that variable:

        my ($line, $status);
        dbms_output.get_line( $conn, \$line, \$status);
        # $line and $status contain the results now

You might need to specify additional options for DBI to know how to bind these variables. You can do so by wrapping the variable reference and the options in an arrayref:

        dbms_output.get_line( $conn, [\$line, 1000], \$status);

The contents of this arrayref will be used in the bind_param_inout method of the statement handle: Above code results in

        $sql->bind_param_inout(1, \$line, 1000);
        $sql->bind_param_inout(2, \$status, 100); # 100 byte default size

If you do not specify options, the parameters will be bound with a default maximum size of 100 bytes.

You can also specify these bind options with IN parameters if you need them.

Please refer to the DBI documentation for details on binding variables.

Attributes

When importing the subroutines, you can optionally specify one or more attributes.

        use DBIx::ProcedureCall qw[
                sysdate:cached
                ];

A few attributes are independent of the database system that you use, but most rely on specific functions of the DBMS implemention. Please see the documentation about the DBMS you are going to use:

DBIx::ProcedureCall::Oracle

DBIx::ProcedureCall::PostgreSQL

The generic attributes are:

:cached

Uses DBI's prepare_cached() instead of the default prepare() , which can increase database performance. See the DBI documentation on how this works.

:fetch

Some stored procedures can return a result set (this topic is covered in the DBMS-specific documentation). DBIx::ProcedureCall provides five :fetch attributes that let you control how this result set is transformed into a Perl data structure, each using a different DBI fetch method. Check the DBI documents for details.

        :fetch()        does  fetchrow_array and returns the first row
                        as a list
        :fetch{}        does fetchrow_hashref and returns the first row
                        as a hashref
        :fetch[]        does fetchrow_arrayref and returns the first row
                        as an arrayref
        :fetch[[]]      does fetchall_arrayref and returns all rows
                        as an arrayref of arrayrefs
        :fetch[{}]      does fetchall_arrayref({}) and returns all 
                        rows as an arrayref of hashrefs

Example:

        use DBIx::ProcedureCall
                qw(  some_query_function:fetch[{}] );
        
        my $data = some_query_function($conn, @params);
        # $data will look like this
        # [  { column_one => 'data', column_two => 'data' },
        #    { column_one => 'data', column_two => 'data' },
        #    .... more rows ....
        #   { column_one => 'data', column_two => 'data' } ]    

ALTERNATIVE WAYS TO PASS IN THE DATABASE HANDLE

        my $result = sysdate($conn);

Having to pass in the database handle as a parameter is a little ugly. If you put your wrapper subroutines into a package you can use the following syntax

        {
                package MyDB;
                use DBIx::ProcedureCall qw( sysdate );
        }
        
        my $result = $conn->MyDB::sysdate()

You are still passing the handle around, but it is visually separated from the "real" parameters.

ALTERNATIVE INTERFACE

If you do not want to import wrapper functions, you can still use the SQL generation and parameter binding mechanism of DBIx::ProcedureCall:

        DBIx::ProcedureCall::run($conn, 'dbms_random.initialize', 12345);

        print DBIx::ProcedureCall::run($conn, 'sysdate');

This can be useful if you do not know the names of the stored procedures at compilation time.

You can also use attributes (except for :package[d], which does not make sense here), with the same syntax as usual:

        DBIx::ProcedureCall::run($conn, 'some_select:fetch[[]]');

COMMAND LINE INTERFACE

There is also a command line interface:

         perl -MDBIx::ProcedureCall::CLI -e function sysdate

See DBIx::ProcedureCall::CLI

SEE ALSO ^

This module is built on top of DBI, and you need to use that module (and the appropriate DBD::xx drivers) to establish a database connection.

You have to read the DBIx::ProcedureCall documentation for the database system that you are using:

DBIx::ProcedureCall::Oracle

DBIx::ProcedureCall::PostgreSQL

LIMITATIONS ^

The module wants to provide an extremely simple interface to the most common forms of stored procedures. It will not be able to handle very complex cases. That is not the goal, if it can eliminate 90% of hand-written SQL and bind calls, I am happy.

Only Oracle and Postgres are supported now. If you want to implement a driver for another data base system, have a look at the source code for the current implementation, and see if you can adapt it. If this leads to working code, let me know, so that I can bundle it.

You cannot mix named and positional parameters

LOB (except for small ones probably) do not work now. Or maybe they do. I have not tried.

You cannot specify a bind buffer size for function return values, and thus cannot get return values that do not fit into the default 100 bytes. A work-around is to use an OUT-parameter (for which you can set a buffer size).

AUTHOR ^

Thilo Planz, <thilo@cpan.org>

COPYRIGHT AND LICENSE ^

Copyright 2004-06 by Thilo Planz

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

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