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Man Pages


Manual Reference Pages  -  DBD::PGPP (3)

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NAME

DBD::PgPP - Pure Perl PostgreSQL driver for the DBI

CONTENTS

SYNOPSIS



  use DBI;

  my $dbh = DBI->connect(dbi:PgPP:dbname=$dbname, , );

  # See the DBI module documentation for full details



DESCRIPTION

DBD::PgPP is a pure-Perl client interface for the PostgreSQL database. This module implements the network protocol that allows a client to communicate with a PostgreSQL server, so you don’t need an external PostgreSQL client library like <B>libpqB> for it to work. That means this module enables you to connect to PostgreSQL server from platforms where there’s no PostgreSQL port, or where installing PostgreSQL is prohibitively hard.

MODULE DOCUMENTATION

This documentation describes driver specific behavior and restrictions; it does not attempt to describe everything you might need to use DBD::PgPP. In particular, users are advised to be familiar with the DBI documentation.

THE DBI CLASS

    DBI Class Methods

<B>connectB> At a minimum, you need to use code like this to connect to the database:



  $dbh = DBI->connect(dbi:PgPP:dbname=$dbname, , );



This connects to the database $dbname on localhost without any user authentication. This may well be sufficient for some PostgreSQL installations.

The following connect statement shows all possible parameters:



  $dbh = DBI->connect("dbi:PgPP:dbname=$dbname", $username, $password);

  $dbh = DBI->connect("dbi:PgPP:dbname=$dbname;host=$host;port=$port",
                      $username, $password);

  $dbh = DBI->connect("dbi:PgPP:dbname=$dbname;path=$path;port=$port",
                      $username, $password);

      parameter | hard coded default
      ----------+-------------------
      dbname    | current userid
      host      | localhost
      port      | 5432
      path      | /tmp
      debug     | undef



If a host is specified, the postmaster on this host needs to be started with the -i option (TCP/IP socket).

For authentication with username and password appropriate entries have to be made in pg_hba.conf. Please refer to the PostgreSQL documentation for pg_hba.conf and pg_passwd for the various types of authentication.

DATABASE-HANDLE METHODS

last_insert_id


    $rv = $dbh->last_insert_id($catalog, $schema, $table, $field);
    $rv = $dbh->last_insert_id($catalog, $schema, $table, $field, \%attr);



Attempts to return the id of the last value to be inserted into a table. Since PostgreSQL uses the sequence type to implement such things, this method finds a sequence’s value using the CURRVAL() PostgreSQL function. This will fail if the sequence has not yet been used in the current database connection.

DBD::PgPP ignores the $catalog and $field arguments are ignored in all cases, but they’re required by DBI itself.

If you don’t know the name of the applicable sequence for the table, you can simply provide a table name (optionally qualified by a schema name), and DBD::PgPP will attempt to work out which sequence will contain the correct value:



    $dbh->do(q{CREATE TABLE t (id serial primary key, s text not null)});
    my $sth = $dbh->prepare(INSERT INTO t (s) VALUES (?));
    for my $value (@values) {
        $sth->execute($value);
        my $id = $dbh->last_insert_id(undef, undef, t, undef);
        print "Inserted $id: $value\n";
    }



In most situations, that is the simplest approach. However, it requires the table to have at least one column which is non-null and unique, and uses a sequence as its default value. (If there is more than one such column, the primary key is used.)

If those requirements aren’t met in your situation, you can alternatively specify the sequence name directly:



    $dbh->do(q{CREATE SEQUENCE t_id_seq START 1});
    $dbh->do(q{CREATE TABLE t (
      id int not null unique DEFAULT nextval(t_id_seq),
      s text not null)});
    my $sth = $dbh->prepare(INSERT INTO t (s) VALUES (?));
    for my $value (@values) {
        $sth->execute($value);
        my $id = $dbh->last_insert_id(undef, undef, undef, undef, {
            sequence => t_id_seq,
        });
        print "Inserted $id: $value\n";
    }



If you adopt the simpler approach, note that DBD::PgPP will have to issue some queries to look things up in the system tables. DBD::PgPP will then cache the appropriate sequence name for subsequent calls. Should you need to disable this caching for some reason, you can supply a true value for the attribute pgpp_cache:



    my $id = $dbh->last_insert_id(undef, undef, $table, undef, {
        pgpp_cache => 0,
    });



Please keep in mind that last_insert_id is far from foolproof, so make your program uses it carefully. Specifically, last_insert_id should be used only immediately after an insert to the table in question, and that insert must not specify a value for the applicable column.

OTHER FUNCTIONS

As of DBD::PgPP 0.06, you can use the following functions to determine the version of the server to which a database handle is connected. Note the unusual calling convention; it may be changed in the future.
DBD::PgPP::pgpp_server_identification($dbh) The server’s version identification string, as returned by the standard version() function available in PostgreSQL 7.2 and above. If the server doesn’t support that function, returns an empty string.
DBD::PgPP::pgpp_server_version($dbh) The server’s version string, as parsed out of the return value of the standard version() function available in PostgreSQL 7.2 and above. For example, returns the string 8.3.5 if the server is release 8.3.5. If the server doesn’t support version(), returns the string 0.0.0.
DBD::PgPP::pgpp_server_version_num($dbh) A number representing the server’s version number, as parsed out of the return value of the standard version() function available in PostgreSQL 7.2 and above. For example, returns 80305 if the server is release 8.3.5. If the server doesn’t support version(), returns zero.

BUGS, LIMITATIONS, AND TODO

o The debug DSN parameter is incorrectly global: if you enable it for one database handle, it gets enabled for all database handles in the current Perl interpreter. It should probably be removed entirely in favour of DBI’s built-in and powerful tracing mechanism, but that’s too hard to do in the current architecture.
o No support for Kerberos or SCM Credential authentication; and there’s no support for crypt authentication on some platforms.
o Can’t use SSL for encrypted connections.
o Using multiple semicolon-separated queries in a single statement will cause DBD::PgPP to fail in a way that requires you to reconnect to the server.
o No support for COPY, or LISTEN notifications, or for cancelling in-progress queries. (There’s also no support for the explicit function call part of the protocol, but there’s nothing you can do that way that isn’t more easily achieved by writing SQL to call the function.)
o There’s currently no way to get informed about any warnings PostgreSQL may issue for your queries.
o No support for BLOB data types or long objects.
o Currently assumes that the Perl code and the database use the same encoding for text; probably also assumes that the encoding uses eight bits per character. Future versions are expected to support UTF-8-encoded Unicode (in a way that’s compatible with Perl’s own string encodings).
o You can’t use any data type that (like bytea) requires $dbh->quote to use any syntax other than standard string literals. Using booleans and numbers works to the extent that PostgreSQL supports string-ish syntax for them, but that varies from one version to another. The only reliable way to solve this and still support PostgreSQL 7.3 and below is to use the DBI bind_param mechanism and say which type you want; but typed bind_param ignores the type at the moment.

DEPENDENCIES

This module requires Perl 5.8 or higher. (If you want it to work under earlier Perl versions, patches are welcome.)

The only module used (other than those which ship with supported Perl versions) is DBI.

SEE ALSO

DBI, DBD::Pg, <http://developer.postgresql.org/docs/postgres/protocol.html>

AUTHOR

Hiroyuki OYAMA <oyama@module.jp>

COPYRIGHT AND LICENCE

Copyright (C) 2004 Hiroyuki OYAMA. All rights reserved. Copyright (C) 2004, 2005, 2009, 2010 Aaron Crane. All rights reserved.

DBD::PgPP is free software; you can redistribute it and/or modify it under the terms of Perl itself, that is to say, under the terms of either:
o The GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version, or
o The Artistic License which comes with Perl.

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perl v5.20.3 DBD::PGPP (3) 2010-01-09

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