# DBI::DBD::Metadata - phpMan

## NAME
    [DBI::DBD::Metadata] - Generate the code and data for some DBI metadata
    methods

## SYNOPSIS
    The idea is to extract metadata information from a good quality ODBC
    driver and use it to generate code and data to use in your own DBI
    driver for the same database.

    To generate code to support the get_info method:

      perl -[MDBI::DBD::Metadata] -e "write_getinfo_pm('dbi:ODBC:dsn-name','user','pass','Driver')"

      perl -[MDBI::DBD::Metadata] -e write_getinfo_pm dbi:ODBC:foo_db username password Driver

    To generate code to support the type_info method:

      perl -[MDBI::DBD::Metadata] -e "write_typeinfo_pm('dbi:ODBC:dsn-name','user','pass','Driver')"

      perl -[MDBI::DBD::Metadata] -e write_typeinfo_pm dbi:ODBC:dsn-name user pass Driver

    Where "dbi:ODBC:dsn-name" is the connection to use to extract the data,
    and "Driver" is the name of the driver you want the code generated for
    (the driver name gets embedded into the output in numerous places).

Generating a GetInfo package for a driver
    The "write_getinfo_pm" in the [DBI::DBD::Metadata] module generates a
    [DBD::Driver::GetInfo] package on standard output.

    This method generates a [DBD::Driver::GetInfo] package from the data
    source you specified in the parameter list or in the environment
    variable DBI_DSN. [DBD::Driver::GetInfo] should help a DBD author
    implement the DBI get_info() method. Because you are just creating this
    package, it is very unlikely that [DBD::Driver] already provides a good
    implementation for get_info(). Thus you will probably connect via
    [DBD::ODBC].

    Once you are sure that it is producing reasonably sane data, you should
    typically redirect the standard output to lib/DBD/Driver/GetInfo.pm, and
    then hand edit the result. Do not forget to update your Makefile.PL and
    MANIFEST to include this as an extra PM file that should be installed.

    If you connect via [DBD::ODBC], you should use version 0.38 or greater;

    Please take a critical look at the data returned! ODBC drivers vary
    dramatically in their quality.

    The generator assumes that most values are static and places these
    values directly in the %info hash. A few examples show the use of CODE
    references and the implementation via subroutines. It is very likely
    that you will have to write additional subroutines for values depending
    on the session state or server version, e.g. SQL_DBMS_VER.

    A possible implementation of [DBD::Driver::db::get_info]() may look like:

      sub get_info {
        my($dbh, $info_type) = @_;
        require [DBD::Driver::GetInfo];
        my $v = $[DBD::Driver::GetInfo::info]{int($info_type)};
        $v = $v->($dbh) if ref $v eq 'CODE';
        return $v;
      }

    Please replace Driver (or "<foo>") with the name of your driver. Note
    that this stub function is generated for you by write_getinfo_pm
    function, but you must manually transfer the code to Driver.pm.

Generating a TypeInfo package for a driver
    The "write_typeinfo_pm" function in the [DBI::DBD::Metadata] module
    generates on standard output the data needed for a driver's
    type_info_all method. It also provides default implementations of the
    type_info_all method for inclusion in the driver's main implementation
    file.

    The driver parameter is the name of the driver for which the methods
    will be generated; for the sake of examples, this will be "Driver".
    Typically, the dsn parameter will be of the form "dbi:ODBC:odbc_dsn",
    where the odbc_dsn is a DSN for one of the driver's databases. The user
    and pass parameters are the other optional connection parameters that
    will be provided to the DBI connect method.

    Once you are sure that it is producing reasonably sane data, you should
    typically redirect the standard output to lib/DBD/Driver/TypeInfo.pm,
    and then hand edit the result if necessary. Do not forget to update your
    Makefile.PL and MANIFEST to include this as an extra PM file that should
    be installed.

    Please take a critical look at the data returned! ODBC drivers vary
    dramatically in their quality.

    The generator assumes that all the values are static and places these
    values directly in the %info hash.

    A possible implementation of [DBD::Driver::type_info_all]() may look like:

      sub type_info_all {
        my ($dbh) = @_;
        require [DBD::Driver::TypeInfo];
        return [ @$[DBD::Driver::TypeInfo::type_info_all] ];
      }

    Please replace Driver (or "<foo>") with the name of your driver. Note
    that this stub function is generated for you by the write_typeinfo_pm
    function, but you must manually transfer the code to Driver.pm.

## AUTHORS
    Jonathan Leffler <<jleffler@us.ibm.com>> (previously
    <<jleffler@informix.com>>), Jochen Wiedmann <<joe@ispsoft.de>>, Steffen
    Goeldner <<sgoeldner@cpan.org>>, and Tim Bunce <<dbi-users@perl.org>>.