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Pali
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NAME

DBD::MariaDB - MariaDB and MySQL driver for the Perl5 Database Interface (DBI)

SYNOPSIS

  use DBI;

  my $dsn = "DBI:MariaDB:database=$database;host=$hostname;port=$port";
  my $dbh = DBI->connect($dsn, $user, $password);

  my $sth = $dbh->prepare(
      'SELECT id, first_name, last_name FROM authors WHERE last_name = ?'
  ) or die 'prepare statement failed: ' . $dbh->errstr();
  $sth->execute('Eggers') or die 'execution failed: ' . $dbh->errstr();
  print $sth->rows() . " rows found.\n";
  while (my $ref = $sth->fetchrow_hashref()) {
      print "Found a row: id = $ref->{'id'}, fn = $ref->{'first_name'}\n";
  }

EXAMPLE

  #!/usr/bin/perl

  use strict;
  use warnings;
  use DBI;

  # Connect to the database.
  my $dbh = DBI->connect('DBI:MariaDB:database=test;host=localhost',
                         'joe', q(joe's password),
                         { RaiseError => 1, PrintError => 0 });

  # Drop table 'foo'. This may fail, if 'foo' doesn't exist
  # Thus we put an eval around it.
  eval {
      $dbh->do('DROP TABLE foo');
  } or do {
      print 'Dropping foo failed: ' . $dbh->errstr() . "\n";
  };

  # Create a new table 'foo'. This must not fail, thus we don't
  # catch errors.
  $dbh->do('CREATE TABLE foo (id INTEGER, name VARCHAR(20))');

  # INSERT some data into 'foo' using placeholders
  $dbh->do('INSERT INTO foo VALUES (?, ?)', undef, 2, 'Jochen');

  # now retrieve data from the table.
  my $sth = $dbh->prepare('SELECT * FROM foo');
  $sth->execute();
  while (my $ref = $sth->fetchrow_hashref()) {
      print "Found a row: id = $ref->{'id'}, name = $ref->{'name'}\n";
  }

  # Disconnect from the database.
  $dbh->disconnect();

DESCRIPTION

DBD::MariaDB is the Perl5 Database Interface driver for MariaDB and MySQL databases. In other words: DBD::MariaDB is an interface between the Perl programming language and the MariaDB/MySQL programming API that comes with the MariaDB/MySQL relational database management system. Most functions provided by this programming API are supported. Some rarely used functions are missing, mainly because no-one ever requested them. :-)

In what follows we first discuss the use of DBD::MariaDB, because this is what you will need the most. For installation, see the separate document DBD::MariaDB::INSTALL. See "EXAMPLE" for a simple example above.

From perl you activate the interface with the statement

  use DBI;

After that you can connect to multiple MariaDB and MySQL database servers and send multiple queries to any of them via a simple object oriented interface. Two types of objects are available: database handles and statement handles. Perl returns a database handle to the connect method like so:

  my $dbh = DBI->connect("DBI:MariaDB:database=$db;host=$host",
                         $user, $password,
                         { RaiseError => 1, PrintError => 0 });

Once you have connected to a database, you can execute SQL statements with:

  $dbh->do('INSERT INTO foo VALUES (?, ?)', undef, $number, $name);

See DBI do method for details. See also the bind_param method in DBI. See "DATABASE HANDLES" below for more details on database handles.

If you want to retrieve results, you need to create a so-called statement handle with:

  my $sth = $dbh->prepare('SELECT * FROM ' . $dbh->quote_identifier($table));
  $sth->execute();

This statement handle can be used for multiple things. First of all you can retrieve a row of data:

  my $row = $sth->fetchrow_hashref();

If your table has columns ID and NAME, then $row will be hash ref with keys ID and NAME. See "STATEMENT HANDLES" below for more details on statement handles.

But now for a more formal approach:

Class Methods

connect
  use DBI;

  my $dsn = "DBI:MariaDB:$database";
  my $dsn = "DBI:MariaDB:database=$database;host=$hostname";
  my $dsn = "DBI:MariaDB:database=$database;host=$hostname;port=$port";
  my $dsn = "DBI:MariaDB:database=$database;mariadb_socket=$socket";

  my $dbh = DBI->connect($dsn, $user, $password);

The database is not a required attribute, but please note that MariaDB and MySQL has no such thing as a default database. If you don't specify the database at connection time your active database will be null and you'd need to prefix your tables with the database name; i.e. SELECT * FROM mydb.mytable.

This is similar to the behavior of the mariadb or mysql command line client. Also, SELECT DATABASE() will return the current database active for the handle.

host
port

The host, if not specified or specified as empty string or localhost, will default to a MariaDB or MySQL server running on the local machine using the default for the UNIX socket. To connect to a MariaDB or MySQL server on the local machine via TCP, you must specify the loopback IP address 127.0.0.1 as the host.

Should the MariaDB or MySQL server be running on a non-standard port number, you may explicitly state the port number to connect to in the host argument, by concatenating the hostname and port number together separated by a colon (:) character or by using the port argument.

To connect to a MariaDB or MySQL server on localhost using TCP/IP, you must specify the host as 127.0.0.1 with the optional port, e.g. 3306.

When connecting to a MariaDB or MySQL Server with IPv6, a bracketed IPv6 address should be used. Example DSN:

  my $dsn = 'DBI:MariaDB:;host=[1a12:2800:6f2:85::f20:8cf];port=3306';
mariadb_client_found_rows

Enables (logical true value) or disables (logical false value) the flag CLIENT_FOUND_ROWS while connecting to the MariaDB or MySQL server. This has a somewhat funny effect. Without mariadb_client_found_rows, if you perform a query like

  UPDATE t SET id = 1 WHERE id = 1;

then the MariaDB or MySQL engine will always return 0, because no rows have changed. With mariadb_client_found_rows however, it will return the number of rows that have an id 1, as some people are expecting. At least for compatibility to other engines.

By default mariadb_client_found_rows is enabled.

mariadb_compression

If your DSN contains the option mariadb_compression=1, then the communication between client and server will be compressed.

mariadb_connect_timeout

If your DSN contains the option mariadb_connect_timeout=##, the connect request to the server will timeout if it has not been successful after the given number of seconds. Zero value means infinite timeout.

mariadb_write_timeout

If your DSN contains the option mariadb_write_timeout=##, the write operation to the server will timeout if it has not been successful after the given number of seconds. Zero value means infinite timeout.

mariadb_read_timeout

If your DSN contains the option mariadb_read_timeout=##, the read operation to the server will timeout if it has not been successful after the given number of seconds. Zero value means infinite timeout.

mariadb_init_command

If your DSN contains the option mariadb_init_command=SQL, then this SQL statement is executed when connecting to the MariaDB or MySQL server. It is automatically re-executed if reconnection occurs.

mariadb_skip_secure_auth

This option is for older MySQL databases that don't have secure auth set.

mariadb_read_default_file
mariadb_read_default_group

These options can be used to read a config file like /etc/my.cnf or ~/.my.cnf. By default MariaDB's and MySQL's C client library doesn't use any config files unlike the client programs (mysql, mysqladmin, ...) that do, but outside of the C client library. Thus you need to explicitly request reading a config file, as in

  my $dsn = 'DBI:MariaDB:test;mariadb_read_default_file=/home/joe/my.cnf';
  my $dbh = DBI->connect($dsn, $user, $password);

The option mariadb_read_default_group can be used to specify the default group in the config file: Usually this is the client group, but see the following example:

  [client]
  host=localhost

  [perl]
  host=perlhost

(Note the order of the entries! The example won't work, if you reverse the [client] and [perl] sections!)

If you read this config file, then you'll be typically connected to localhost. However, by using

  my $dsn = 'DBI:MariaDB:test;mariadb_read_default_group=perl;'
          . 'mariadb_read_default_file=/home/joe/my.cnf';
  my $dbh = DBI->connect($dsn, $user, $password);

you'll be connected to perlhost. Note that if you specify a default group and do not specify a file, then the default config files will all be read. See the documentation of the C function mysql_options() for details.

mariadb_socket

It is possible to choose the Unix socket that is used for connecting to the server. This is done, for example, with

  my $dsn = 'DBI:MariaDB:database=test;'
          . 'mariadb_socket=/var/run/mysqld/mysqld.sock';

Usually there's no need for this option, unless you are using another location for the socket than that built into the client.

mariadb_ssl

A true value turns on the CLIENT_SSL flag when connecting to the MariaDB or MySQL server and enforce SSL encryption. A false value (which is default) disable SSL encryption with the MariaDB or MySQL server.

When enabling SSL encryption you should set also other SSL options, at least mariadb_ssl_ca_file or mariadb_ssl_ca_path.

  my $dsn = 'DBI:MariaDB:database=test;host=hostname;port=3306;'
          . 'mariadb_ssl=1;mariadb_ssl_verify_server_cert=1;'
          . 'mariadb_ssl_ca_file=/path/to/ca_cert.pem';

This means that your communication with the server will be encrypted.

mariadb_ssl_ca_file

The path to a file in PEM format that contains a list of trusted SSL certificate authorities.

When set MariaDB or MySQL server certificate is checked that it is signed by some CA certificate in the list. Common Name value is not verified unless mariadb_ssl_verify_server_cert is enabled.

mariadb_ssl_ca_path

The path to a directory that contains trusted SSL certificate authority certificates in PEM format.

When set MariaDB or MySQL server certificate is checked that it is signed by some CA certificate in the list. Common Name value is not verified unless mariadb_ssl_verify_server_cert is enabled.

Please note that this option is supported only if your MariaDB or MySQL client was compiled with OpenSSL library, and not with default yaSSL library.

mariadb_ssl_verify_server_cert

Checks the server's Common Name value in the certificate that the server sends to the client. The client verifies that name against the host name the client uses for connecting to the server, and the connection fails if there is a mismatch. For encrypted connections, this option helps prevent man-in-the-middle attacks.

Verification of the host name is disabled by default.

mariadb_ssl_client_key

The name of the SSL key file in PEM format to use for establishing a secure connection.

mariadb_ssl_client_cert

The name of the SSL certificate file in PEM format to use for establishing a secure connection.

mariadb_ssl_cipher

A list of permissible ciphers to use for connection encryption. If no cipher in the list is supported, encrypted connections will not work.

  mariadb_ssl_cipher=AES128-SHA
  mariadb_ssl_cipher=DHE-RSA-AES256-SHA:AES128-SHA
mariadb_ssl_optional

Setting mariadb_ssl_optional to true disables strict SSL enforcement and makes SSL connection optional. This option opens security hole for man-in-the-middle attacks. Default value is false which means that mariadb_ssl set to true enforces SSL encryption.

Due to The BACKRONYM and The Riddle vulnerabilities in libmariadb and libmysqlclient libraries, enforcement of SSL encryption was not possible and therefore mariadb_ssl_optional=1 was effectively set for old DBD::mysql driver prior DBD::MariaDB fork was created. DBD::MariaDB with mariadb_ssl=1 could refuse connection to MariaDB or MySQL server if underlying libmariadb or libmysqlclient library is vulnerable. Option mariadb_ssl_optional can be used to make SSL connection vulnerable.

mariadb_local_infile

The LOCAL capability for LOAD DATA may be disabled in the MariaDB or MySQL client library by default. If your DSN contains the option mariadb_local_infile=1, LOAD DATA LOCAL will be enabled. However, this option is ineffective if the server has also been configured to disallow LOCAL.

mariadb_multi_statements

Support for multiple statements separated by a semicolon (;) may be enabled by using this option. Enabling this option may cause problems if server-side prepared statements are also enabled.

mariadb_server_prepare

This option is used to enable server side prepared statements. By default prepared statements are not used and placeholder replacement is done by DBD::MariaDB prior to sending SQL statement to MariaDB or MySQL server.

This default behavior may change in the future.

To use server side prepared statements, all you need to do is set the variable mariadb_server_prepare in the connect:

  my $dbh = DBI->connect(
      'DBI:MariaDB:database=test;host=localhost;mariadb_server_prepare=1',
      'user',
      'password',
      { RaiseError => 1, PrintError => 0 },
  );

or:

  my $dbh = DBI->connect(
      'DBI:MariaDB:database=test;host=localhost',
      'user',
      'password',
      { RaiseError => 1, PrintError => 0, mariadb_server_prepare => 1 },
  );

There are many benefits to using server side prepare statements, mostly if you are using SQL statements with placeholders or performing many inserts because of that fact that a single statement is prepared to accept multiple insert values.

Please note that MariaDB or MySQL server cannot prepare or execute some prepared statements. In this case DBD::MariaDB fallbacks to normal non-prepared statement and tries again.

mariadb_server_prepare_disable_fallback

This option disable fallback to normal non-prepared statement when MariaDB or MySQL server does not support execution of current statement as prepared.

Useful when you want to be sure that the statement is going to be executed as server side prepared. Error message and code in case of failure is propagated back to DBI.

This default behavior may change in the future.

mariadb_embedded_options

The option mariadb_embedded_options can be used to pass command line options to the embedded server. When you want to start and connect embedded server, use host=embedded in dsn as connection parameter.

Example:

  use DBI;
  my $datadir = '/var/lib/mysql/';
  my $langdir = '/usr/share/mysql/english';
  my $dsn = 'DBI:MariaDB:host=embedded;database=test;'
          . "mariadb_embedded_options=--datadir=$datadir,--language=$langdir";
  my $dbh = DBI->connect($dsn, undef, undef);

This would start embedded server with language directory $langdir, database directory $datadir and connects to database test. Embedded server does not have to be supported by configured MariaDB or MySQL library. In that case DBI->connect() returns an error.

mariadb_embedded_groups

The option mariadb_embedded_groups can be used to specify the groups in the config file (my.cnf) which will be used to get options for the embedded server. If not specified [server] and [embedded] groups will be used.

Example:

  my $dsn = 'DBI:MariaDB:host=embedded;database=test;'
          . 'mariadb_embedded_groups=embedded_server,common';
mariadb_conn_attrs

The option mariadb_conn_attrs is a hash of attribute names and values which can be used to send custom connection attributes to the server. Some attributes like _os, _platform, _client_name and _client_version are added by libmariadb or libmysqlclient.

You can then later read these attributes from the performance schema tables which can be quite helpful for profiling your database or creating statistics. You'll have to use both server and client at least in version MariaDB 10.0.5 or MySQL 5.6 to leverage this feature. It is a good idea to provides additional program_name attribute.

  my $dbh= DBI->connect($dsn, $user, $password, {
      AutoCommit => 0,
      mariadb_conn_attrs => {
          program_name => $0,
          foo => 'bar',
          wiz => 'bang'
      },
  });

Now you can select the results from the performance schema tables. You can do this in the same session, but also afterwards. It can be very useful to answer questions like which script sent this query?

  my $results = $dbh->selectall_hashref(
      'SELECT * FROM performance_schema.session_connect_attrs',
      'ATTR_NAME'
  );

This returns:

  $result = {
      '_client_name' => {
          'ATTR_VALUE'       => 'libmysql',
          'ATTR_NAME'        => '_client_name',
          'ORDINAL_POSITION' => '1',
          'PROCESSLIST_ID'   => '3',
      },
      '_client_version' => {
          'ATTR_VALUE'       => '5.6.24',
          'ATTR_NAME'        => '_client_version',
          'ORDINAL_POSITION' => '7',
          'PROCESSLIST_ID'   => '3',
      },
      '_os' => {
          'ATTR_VALUE'       => 'osx10.8',
          'ATTR_NAME'        => '_os',
          'ORDINAL_POSITION' => '0',
          'PROCESSLIST_ID'   => '3',
      },
      '_pid' => {
          'ATTR_VALUE'       => '59860',
          'ATTR_NAME'        => '_pid',
          'ORDINAL_POSITION' => '2',
          'PROCESSLIST_ID'   => '3',
      },
      '_platform' => {
          'ATTR_VALUE'       => 'x86_64',
          'ATTR_NAME'        => '_platform',
          'ORDINAL_POSITION' => '4',
          'PROCESSLIST_ID'   => '3',
      },
      'foo' => {
          'ATTR_NAME'        => 'foo',
          'ATTR_VALUE'       => 'bar',
          'ORDINAL_POSITION' => '6',
          'PROCESSLIST_ID'   => '3',
      },
      'program_name' => {
          'ATTR_VALUE'       => './foo.pl',
          'ATTR_NAME'        => 'program_name',
          'ORDINAL_POSITION' => '5',
          'PROCESSLIST_ID'   => '3',
      },
      'wiz' => {
          'ATTR_VALUE'       => 'bang',
          'ATTR_NAME'        => 'wiz',
          'ORDINAL_POSITION' => '3',
          'PROCESSLIST_ID'   => '3',
      },
  };
data_sources
  use DBI;
  my @dsns = DBI->data_sources('MariaDB', {
      host => $hostname,
      port => $port,
      user => $username,
      password => $password,
      ...
  });

Returns a list of all databases in dsn format suitable for connect method, managed by the MariaDB or MySQL server. It accepts all attributes from connect method.

DATABASE HANDLES

The DBD::MariaDB driver supports the following attributes of database handles (read only):

  my $errno = $dbh->{'mariadb_errno'};
  my $error = $dbh->{'mariadb_error'};
  my $hostinfo = $dbh->{'mariadb_hostinfo'};
  my $info = $dbh->{'mariadb_info'};
  my $insertid = $dbh->{'mariadb_insertid'};
  my $protoinfo = $dbh->{'mariadb_protoinfo'};
  my $serverinfo = $dbh->{'mariadb_serverinfo'};
  my $ssl_cipher = $dbh->{'mariadb_ssl_cipher'};
  my $stat = $dbh->{'mariadb_stat'};
  my $thread_id = $dbh->{'mariadb_thread_id'};

These correspond to mysql_errno(), mysql_error(), mysql_get_host_info(), mysql_info(), mysql_insert_id(), mysql_get_proto_info(), mysql_get_server_info(), mysql_stat(), mysql_get_ssl_cipher() and mysql_thread_id() respectively.

Portable DBI applications should not use them. Instead they should use standard DBI methods: $dbh->err() and $dbh->errstr() for error number and string, $dbh->get_info($GetInfoType{SQL_SERVER_NAME}) for server host name, $dbh->get_info($GetInfoType{SQL_DBMS_NAME}) and $dbh->get_info($GetInfoType{SQL_DBMS_VER}) for server database name and version, $dbh->last_insert_id() or $sth->last_insert_id() for insert id.

mariadb_clientinfo
mariadb_clientversion

List information of the MariaDB or MySQL client library that DBD::MariaDB was built against:

  print "$dbh->{mariadb_clientinfo}\n";

  5.2.0-MariaDB

  print "$dbh->{mariadb_clientversion}\n";

  50200

Portable DBI applications should not be interested in version of underlying client library. DBD::MariaDB is there to hide any possible incompatibility and works correctly with any available version.

mariadb_serverversion
  print "$dbh->{mariadb_serverversion}\n";

  50200

Portable DBI applications should use $dbh->get_info($GetInfoType{SQL_DBMS_NAME}) and $dbh->get_info($GetInfoType{SQL_DBMS_VER}) for server database name and version instead.

mariadb_ssl_cipher

Returns the SSL encryption cipher used for the given connection to the server. In case SSL encryption was not enabled with mariadb_ssl or was not established returns undef.

  my $ssl_cipher = $dbh->{mariadb_ssl_cipher};
  if (defined $ssl_cipher) {
      print "Connection with server is encrypted with cipher: $ssl_cipher\n";
  } else {
      print "Connection with server is not encrypted\n";
  }
mariadb_dbd_stats
  my $info_hashref = $dbh->{mariadb_dbd_stats};

DBD::MariaDB keeps track of some statistics in the mariadb_dbd_stats attribute. The following stats are being maintained:

auto_reconnects_ok

The number of times that DBD::MariaDB successfully reconnected to the MariaDB or MySQL server.

auto_reconnects_failed

The number of times that DBD::MariaDB tried to reconnect to MariaDB or MySQL but failed.

The DBD::MariaDB driver also supports the following attributes of database handles (read/write):

mariadb_auto_reconnect

This attribute determines whether DBD::MariaDB will automatically reconnect to MariaDB or MySQL server if the connection be lost. This feature defaults to off. Setting mariadb_auto_reconnect to 1 is not advised if LOCK TABLES is used because if DBD::MariaDB reconnect to MariaDB or MySQL server all table locks will be lost. This attribute is ignored when AutoCommit is turned off, and when AutoCommit is turned off, DBD::MariaDB will not automatically reconnect to the server.

It is also possible to set the default value of the mariadb_auto_reconnect attribute for the $dbh by passing it in the \%attr hash for DBI->connect.

  $dbh->{mariadb_auto_reconnect} = 1;

or

  my $dbh = DBI->connect($dsn, $user, $password, {
      mariadb_auto_reconnect => 1,
  });

Note that if you are using a module or framework that performs reconnections for you (for example DBIx::Connector in fixup mode), this value must be set to 0.

mariadb_use_result

This attribute forces the driver to use mysql_use_result() rather than mysql_store_result() library function. The former is faster and less memory consuming, but tends to block other processes. mysql_store_result() is the default due to that fact storing the result is expected behavior with most applications.

It is possible to set the default value of the mariadb_use_result attribute for the $dbh via the DSN:

  my $dbh = DBI->connect('DBI:MariaDB:test;mariadb_use_result=1', $user, $pass);

You can also set it after creation of the database handle:

  $dbh->{mariadb_use_result} = 0; # disable
  $dbh->{mariadb_use_result} = 1; # enable

You can also set or unset the mariadb_use_result setting on your statement handle, when creating the statement handle or after it has been created. See "STATEMENT HANDLES".

mariadb_bind_type_guessing

This attribute causes the driver (emulated prepare statements) to attempt to guess if a value being bound is a numeric value, and if so, doesn't quote the value. This was created by Dragonchild and is one way to deal with the performance issue of using quotes in a statement that is inserting or updating a large numeric value.

CAVEAT: Even though you can insert an integer value into a character column, if this column is indexed, if you query that column with the integer value not being quoted, it will not use the index:

  MariaDB [test]> explain select * from test where value0 = '3' \G
  *************************** 1. row ***************************
             id: 1
    select_type: SIMPLE
          table: test
           type: ref
  possible_keys: value0
            key: value0
        key_len: 13
            ref: const
           rows: 1
          Extra: Using index condition
  1 row in set (0.00 sec)

  MariaDB [test]> explain select * from test where value0 = 3
      -> \G
  *************************** 1. row ***************************
             id: 1
    select_type: SIMPLE
          table: test
           type: ALL
  possible_keys: value0
            key: NULL
        key_len: NULL
            ref: NULL
           rows: 6
          Extra: Using where
  1 row in set (0.00 sec)

See bug: https://rt.cpan.org/Public/Bug/Display.html?id=43822

mariadb_bind_type_guessing can be turned on via

- through DSN

  my $dbh = DBI->connect('DBI:MariaDB:test', 'username', 'pass', {
      mariadb_bind_type_guessing => 1
  });

- OR after handle creation

  $dbh->{mariadb_bind_type_guessing} = 1;
mariadb_bind_comment_placeholders

This attribute causes the driver (emulated prepare statements) will cause any placeholders in comments to be bound. This is not correct prepared statement behavior, but some developers have come to depend on this behavior.

mariadb_no_autocommit_cmd

This attribute causes the driver to not issue SET AUTOCOMMIT either through explicit or using mysql_autocommit(). This is particularly useful in the case of using MySQL Proxy.

See the bug report: https://rt.cpan.org/Public/Bug/Display.html?id=46308

mariadb_no_autocommit_cmd can be turned on when creating the database handle:

  my $dbh = DBI->connect('DBI:MariaDB:test', 'username', 'pass', {
      mariadb_no_autocommit_cmd => 1
  });

or using an existing database handle:

  $dbh->{mariadb_no_autocommit_cmd} = 1;
mariadb_max_allowed_packet

This attribute controls the maximum size of one packet, any generated or intermediate string and any bind parameter. Default value depends on client MariaDB/MySQL library and should be 1GB.

  $dbh->{mariadb_max_allowed_packet} = 32*1024*1024; # limit max size to 32MB

Documentation for some DBD::MariaDB methods of database handles:

ping

This can be used to send a ping to the server. See DBI ping.

  my $rc = $dbh->ping();
get_info

This method can be used to retrieve information about MariaDB or MySQL server. See DBI get_info. Some useful information: SQL_DBMS_NAME returns server database name, either MariaDB or MySQL. SQL_DBMS_VER returns server database version and SQL_SERVER_NAME returns server host name.

  use DBI::Const::GetInfoType;

  print $dbh->get_info($GetInfoType{SQL_DBMS_NAME});

  MariaDB

  print $dbh->get_info($GetInfoType{SQL_DBMS_VER});

  10.01.2600

  print $dbh->get_info($GetInfoType{SQL_SERVER_NAME});

  Localhost via UNIX socket

STATEMENT HANDLES

The statement handles of DBD::MariaDB support a number of attributes. You access these by using, for example,

  my $numFields = $sth->{NUM_OF_FIELDS};

Note, that most attributes are valid only after a successful execute. An undef value will returned otherwise. The most important exception is the mariadb_use_result attribute.

To set the mariadb_use_result attribute on statement handle $sth, use either of the following:

  my $sth = $dbh->prepare($sql, { mariadb_use_result => 1});

or

  my $sth = $dbh->prepare($sql);
  $sth->{mariadb_use_result} = 1;

Column dependent attributes, for example NAME, the column names, are returned as a reference to an array. The array indices are corresponding to the indices of the arrays returned by fetchrow and similar methods. For example the following code will print a header of table names together with all rows:

  my $sth = $dbh->prepare('SELECT * FROM t')
      or die 'Error: ' . $dbh->errstr() . "\n";

  $sth->execute()
      or die 'Error: ' . $sth->errstr() . "\n";

  my $names = $sth->{NAME};
  my $numFields = $sth->{'NUM_OF_FIELDS'} - 1;
  for my $i ( 0..$numFields ) {
      printf('%s%s', $i ? ',' : '', $$names[$i]);
  }
  print "\n";
  while (my $ref = $sth->fetchrow_arrayref()) {
      for my $i ( 0..$numFields ) {
          printf('%s%s', $i ? ',' : '', $$ref[$i]);
      }
      print "\n";
  }

For portable applications you should restrict yourself to attributes with capitalized or mixed case names. Lower case attribute names are private to DBD::MariaDB. The attribute list includes:

ChopBlanks

This attribute determines whether a fetchrow will chop preceding and trailing blanks off the column values. Chopping blanks does not have impact on the mariadb_max_length attribute.

mariadb_insertid

If the statement you executed performs an INSERT, and there is an AUTO_INCREMENT column in the table you inserted in, this attribute holds the value stored into the AUTO_INCREMENT column, if that value is automatically generated, by storing NULL or 0 or was specified as an explicit value.

Typically, you'd access the value via $sth->{mariadb_insertid}. The value can also be accessed via $dbh->{mariadb_insertid} but this can easily produce incorrect results in case one database handle is shared.

Portable DBI applications should not use mariadb_insertid. Instead they should use DBI method $dbh->last_insert_id() or statement DBI method $sth->last_insert_id(). Statement method was introduced in DBI version 1.642, but DBD::MariaDB implements it also for older DBI versions.

mariadb_is_blob

Reference to an array of boolean values; Logical true value indicates, that the respective column is a blob.

mariadb_is_key

Reference to an array of boolean values; Logical true value indicates, that the respective column is a key.

mariadb_is_num

Reference to an array of boolean values; Logical true value indicates, that the respective column contains numeric values.

mariadb_is_pri_key

Reference to an array of boolean values; Logical true value indicates, that the respective column is a primary key.

mariadb_is_auto_increment

Reference to an array of boolean values; Logical true value indicates that the respective column is an AUTO_INCREMENT column.

mariadb_length
mariadb_max_length

A reference to an array of maximum column sizes. The mariadb_max_length is the maximum physically present in the result table, mariadb_length gives the theoretically possible maximum.

For string orientated variable types (char, varchar, text and similar types) both attributes return value in bytes. If you are interested in number of characters then instead of mariadb_length use COLUMN_SIZE via standard DBI method column_info and instead of mariadb_max_length issue SQL query SELECT MAX(CHAR_LENGTH(...)). Example:

  my $ci_sth = $dbh->column_info(undef, undef, $table, $column);
  my $ci_ref = $ci_sth->fetchall_arrayref({});
  my $mariadb_char_length = $ci_ref->[0]->{COLUMN_SIZE};

  my $mariadb_char_max_length = $dbh->selectrow_array(sprintf(
                                    'SELECT MAX(CHAR_LENGTH(%s)) FROM %s',
                                    $dbh->quote_identifier($column),
                                    $dbh->quote_identifier($table),
                                ));
NAME

A reference to an array of column names.

NULLABLE

A reference to an array of boolean values; Logical true value indicates that this column may contain NULL's.

NUM_OF_FIELDS

Number of fields returned by a SELECT statement. You may use this for checking whether a statement returned a result: A zero value indicates a non-SELECT statement like INSERT, DELETE or UPDATE.

mariadb_table

A reference to an array of table names, useful in a JOIN result.

TYPE

A reference to an array of column types. The engine's native column types are mapped to portable types like DBI::SQL_INTEGER() or DBI::SQL_VARCHAR(), as good as possible. Not all native types have a meaningful equivalent. If you need the native column types, use mariadb_type. See below.

mariadb_type

A reference to an array of MySQL's native column types, for example DBD::MariaDB::TYPE_SHORT() or DBD::MariaDB::TYPE_STRING(). Use the TYPE attribute, if you want portable types like DBI::SQL_SMALLINT() or DBI::SQL_VARCHAR().

mariadb_type_name

Similar to mariadb_type, but type names and not numbers are returned. Whenever possible, the ANSI SQL name is preferred.

mariadb_warning_count

The number of warnings generated during execution of the SQL statement. This attribute is available on both statement handles and database handles.

UNICODE SUPPORT

All string orientated variable types (char, varchar, text and similar types) are represented by the DBD::MariaDB as Unicode strings according to the standard Perl Unicode model. It means that Perl scalars contain Unicode code points and not UTF-8 bytes. Internally the DBD::MariaDB uses the MySQL's utf8mb4 charset for the network communication with MariaDB and MySQL servers. It automatically transforms the network MySQL's utf8mb4 charset to the Unicode Perl scalars and vice-versa.

MySQL's utf8mb4 charset for the network communication is configured by MYSQL_SET_CHARSET_NAME libmariadb/libmysqlclient C library API which is a requirement to have working quote method and an emulated client side placeholders replacement.

Do not try to change network charset (e.g. via SQL command SET NAMES manually) to anything different then UTF-8 as it would confuse underlying C library and DBD::MariaDB would misbehave (e.g. would lead to broken/insecure quote method or an emulated client side placeholders replacement).

Using a non-UTF-8 charset for a column, table or database is fine because MariaDB or MySQL server automatically transforms the storage charset to the charset used by the network protocol (utf8mb4). Note that when DBD::MariaDB is connecting to the MariaDB or MySQL server it calls SQL command SET character_set_server = 'utf8mb4' to ensure that the default charset for new databases would be UTF-8. Beware that a default charset for new tables is set from a database charset.

In the case MySQL server does not support MySQL's utf8mb4 charset for a network protocol then DBD::MariaDB would try to use MySQL's utf8 charset which is a subset of UTF-8 encoding restricted to the 3 byte UTF-8 sequences. Support for MySQL's utf8mb4 charset was introduced in MySQL server version 5.5.3.

Working with binary data

Perl scalars do not distinguish between binary byte orientated buffers and Unicode orientated strings. In Perl it is always up to the caller and the callee to define in its API if functions and methods expect byte buffers or Unicode strings. It is not possible (or rather Perl application should not try) to distinguish if Perl scalar contains a byte buffer or Unicode string.

When fetching data from MariaDB and MySQL servers, DBD::MariaDB treats all fields marked with MySQL's charset utf8mb4 (and also utf8) as Unicode strings. Everything else is treated as binary byte oriented buffers. Therefore, the only difference is that UTF-8 fields are automatically decoded to Unicode. Binary blob fields remain untouched and corresponding Perl scalars would contain just ordinals 0..255 (classic sequence of bytes). Unicode string scalars would contain sequence of Unicode code points.

There is a small problem with input data, more preciously with SQL statements and their bind parameters. By definition a SQL statement is a string and therefore it is expected and handled by DBD::MariaDB as a Unicode string (not byte oriented buffer). There is no way to treat a SQL statement as a binary, but this is not a problem. All SQL commands are encoded in ASCII and all ASCII characters are invariants in UTF-8 (have the same representation as a sequence of Unicode code points and also when UTF-8 encoded in a byte buffer). For the remaining part of a SQL statement, placeholders with bind parameters can and should be used.

Binary parameters

Unfortunately, neither MariaDB nor MySQL server provide any type information for prepared SQL statements; therefore, DBD::MariaDB has absolutely no way to know if a particular bind parameter for a placeholder should be treated as Unicode string or as byte oriented buffer. So Perl applications which use DBD::MariaDB must provide information about the correct type.

Moreover, DBI API for do, execute and all select* methods binds all parameters as SQL_VARCHAR type. Currently it is an API limitation which does not allow one to specify the bind type. Varchar is a string and so DBD::MariaDB treats all of them as Unicode strings.

The only way how to specify a type in DBI is via the bind_param method. Its third argument takes SQL_* constant which defines a type for the passed bind parameter.

Following type constants are treated as binary by DBD::MariaDB: SQL_BIT, SQL_BLOB, SQL_BINARY, SQL_VARBINARY, SQL_LONGVARBINARY.

This approach of handling binary data was implemented in DBD::MariaDB because it does not violate how Perl's Unicode model is working, follows exactly DBI API documentation, and, more importantly, is how other DBI drivers (including DBD::Pg and DBD::SQLite) in their recent versions work. This ensures good compatibility for Perl applications which use multiple database backends and several DBI drivers.

Please note that the old DBD::mysql driver in version 4.041 works differently and has completely broken Unicode support.

To illustrate the usage, see the following example:

  # Prepare statement
  my $sth = $dbh->prepare(
      'INSERT INTO users (id, name, picture) VALUES (?, ?, ?)'
  );

  # Bind number, 7-bit ASCII values are always in Unicode and binary context
  $sth->bind_param(1, 10);

  # Bind name, may contains Unicode character, in this case U+00E9
  $sth->bind_param(2, "Andr\x{E9}");

  # Bind picture, it is a sequence of binary bytes, not Unicode code points
  $sth->bind_param(3, "\x{D8}\x{A0}\x{39}\x{F8}", DBI::SQL_BINARY);

  # Execute statement with bind parameters
  $sth->execute();

Explanation: In this case number 10 and name "Andr\x{E9}" would be automatically encoded from Perl Unicode string scalars to MySQL's utf8mb4 network charset and picture would not be touched as it was bound with the DBI::SQL_BINARY type. Note that 7-bit ASCII values are invariants in UTF-8, they have the same representations in UTF-8, so both the encoding and decoding operations are just identity functions.

This is the preferred and safe way how to work with binary data. It is also supported by other DBI drivers, including DBD::Pg and DBD::SQLite (see above).

In DBD::MariaDB, there's another specific way how to create a SQL statement with binary data: to call the quote method while specifying a binary type. This method takes a bind parameter and properly quotes + escapes it. For binary types it converts argument to MySQL's HEX syntax (X'...') which is a pure 7-bit ASCII and therefore invariant for UTF-8. See the following example:

  my $param1 = 10;
  my $param2 = "Andr\x{E9}";
  my $param3 = "\x{D8}\x{A0}\x{39}\x{F8}";
  my $query = 'INSERT INTO users (id, name, picture) VALUES (' .
                $dbh->quote($param1) . ' ,' .
                $dbh->quote($param2) . ' ,' .
                $dbh->quote($param3, DBI::SQL_BINARY) .
              ')';
  $dbh->do($query);

The first two parameters are quoted and escaped for a later UTF-8 encoding (to MySQL's utf8mb4 charset) and the third parameter is quoted and escaped as a binary buffer to MySQL's HEX syntax for binary blobs.

This method is not recommended, because quoting, escaping and similar methods can easily get written incorrectly and lead to SQL injections and other security problems.

TRANSACTION SUPPORT

The transaction support works as follows:

  • By default AutoCommit mode is on, following the DBI specifications.

  • If you execute

      $dbh->{AutoCommit} = 0;

    or

      $dbh->{AutoCommit} = 1;

    then the driver will set the MariaDB or MySQL server variable autocommit to 0 or 1, respectively. Switching from 0 to 1 will also issue a COMMIT, following the DBI specifications.

  • The methods

      $dbh->rollback();
      $dbh->commit();

    will issue the commands ROLLBACK and COMMIT, respectively. A ROLLBACK will also be issued if AutoCommit mode is off and the database handles DESTROY method is called. Again, this is following the DBI specifications.

Given the above, you should note the following:

  • You should never change the server variable AutoCommit manually, unless you are ignoring DBI's transaction support.

  • Switching AutoCommit mode from on to off or vice versa may fail. You should always check for errors when changing AutoCommit mode. The suggested way of doing so is using the DBI flag RaiseError. If you don't like RaiseError, you have to use code like the following:

      $dbh->{AutoCommit} = 0;
      if ($dbh->{AutoCommit}) {
          # An error occurred!
      }
  • If you detect an error while changing the AutoCommit mode, you should no longer use the database handle. In other words, you should disconnect and reconnect again, because the transaction mode is unpredictable. Alternatively you may verify the transaction mode by checking the value of the server variable autocommit. However, such behaviour isn't portable.

  • DBD::MariaDB has a reconnect feature that handles the so-called MySQL morning bug: If the server has disconnected, most probably due to a timeout, then by default the driver will reconnect and attempt to execute the same SQL statement again. However, this behaviour is disabled when AutoCommit is off: Otherwise the transaction state would be completely unpredictable after a reconnect.

  • The reconnect feature of DBD::MariaDB can be toggled by using the mariadb_auto_reconnect attribute. This behaviour should be turned off in code that uses LOCK TABLE because if the database server time out and DBD::MariaDB reconnect, table locks will be lost without any indication of such loss.

MULTIPLE RESULT SETS

DBD::MariaDB supports multiple result sets, thanks to Guy Harrison!

The basic usage of multiple result sets is

  do {
      while (my @row = $sth->fetchrow_array()) {
          do stuff;
      }
  } while ($sth->more_results);

An example would be:

  $dbh->do('drop procedure if exists someproc')
      or print $DBI::errstr;

  $dbh->do('create procedure someproc() deterministic
      begin
          declare a,b,c,d int;
          set a=1;
          set b=2;
          set c=3;
          set d=4;
          select a, b, c, d;
          select d, c, b, a;
          select b, a, c, d;
          select c, b, d, a;
      end'
  ) or die "$DBI::err: $DBI::errstr";

  my $sth = $dbh->prepare('call someproc()')
      or die "$DBI::err: $DBI::errstr";

  $sth->execute()
      or die "$DBI::err: $DBI::errstr";

  my $i=0;
  do {
      print "\nRowset ".++$i."\n---------------------------------------\n\n";
      foreach my $colno (0..$sth->{NUM_OF_FIELDS}-1) {
          print $sth->{NAME}->[$colno]."\t";
      }
      print "\n";
      while (my @row = $sth->fetchrow_array())  {
          foreach $field (0..$#row) {
              print $row[$field]."\t";
          }
          print "\n";
      }
  } while ($sth->more_results);

Issues with multiple result sets

Please be aware there could be issues if your result sets are jagged, meaning the number of columns of your results vary. Varying numbers of columns could result in your script crashing.

MULTITHREADING

The multithreading capabilities of DBD::MariaDB depend completely on the underlying C libraries. The modules are working with handle data only, no global variables are accessed or (to the best of my knowledge) thread unsafe functions are called. Thus DBD::MariaDB is believed to be completely thread safe, if the C libraries are thread safe and you don't share handles among threads.

The obvious question is: Are the C libraries thread safe? In the case of MySQL the answer is yes, since MySQL 5.5 it is. Older versions C library needs to be compiled with --with-thread-safe-client or --enable-thread-safe-client configure options.

ASYNCHRONOUS QUERIES

You can make a single asynchronous query per MySQL connection; this allows you to submit a long-running query to the server and have an event loop inform you when it's ready. An asynchronous query is started by either setting the mariadb_async attribute to a true value in the do method, or in the prepare method. Statements created with mariadb_async set to true in prepare always run their queries asynchronously when execute is called. The driver also offers three additional methods: mariadb_async_result(), mariadb_async_ready(), and mariadb_sockfd(). mariadb_async_result() returns what do or execute would have; that is, the number of rows affected. mariadb_async_ready() returns true if mariadb_async_result() will not block, and zero otherwise. They both return undef if that handle was not created with mariadb_async set to true or if an asynchronous query was not started yet. mariadb_sockfd() returns the file descriptor number for the MySQL connection; you can use this in an event loop.

Here's an example of how to use the asynchronous query interface:

  use feature 'say';
  $dbh->do('SELECT SLEEP(10)', { mariadb_async => 1 });
  until($dbh->mariadb_async_ready()) {
      say 'not ready yet!';
      sleep 1;
  }
  my $rows = $dbh->mariadb_async_result();

INSTALLATION

See DBD::MariaDB::INSTALL.

AUTHORS

Originally, there was a non-DBI driver, Mysql, which was much like PHP drivers such as mysql and mysqli. The Mysql module was originally written by Andreas König (koenig@kulturbox.de) who still, to this day, contributes patches to DBD::mysql. An emulated version of Mysql was provided to DBD::mysql from Jochen Wiedmann, but eventually deprecated as it was another bundle of code to maintain.

The first incarnation of DBD::mysql was developed by Alligator Descartes, who was also aided and abetted by Gary Shea, Andreas König and Tim Bunce.

The current incarnation of DBD::mysql was written by Jochen Wiedmann, then numerous changes and bug-fixes were added by Rudy Lippan. Next, prepared statement support was added by Patrick Galbraith and Alexy Stroganov (who also solely added embedded server support).

Since 2004 DBD::mysql has been maintained by Patrick Galbraith (patg@patg.net), and since 2013 with the great help of Michiel Beijen (michiel.beijen@gmail.com), along with the entire community of Perl developers who keep sending patches to help continue improving DBD::mysql.

In 2018 unreleased version 4.042_01 of DBD::mysql was forked and DBD::MariaDB was created to fix long standing Unicode bugs and MariaDB support. Currently it is developed in GoodData and maintained by Pali (pali@cpan.org).

CONTRIBUTIONS

Anyone who desires to contribute to this project is encouraged to do so. Currently, the source code for this project can be found at Github:

https://github.com/gooddata/DBD-MariaDB

Either fork this repository and produce a branch with your changeset that the maintainer can merge to his tree, or create a diff with git. The maintainer is more than glad to take contributions from the community as many features and fixes from DBD::MariaDB have come from the community.

COPYRIGHT

This module is

  • Large Portions Copyright (c) 2018 GoodData Corporation

  • Large Portions Copyright (c) 2015-2017 Pali Rohár

  • Large Portions Copyright (c) 2004-2017 Patrick Galbraith

  • Large Portions Copyright (c) 2013-2017 Michiel Beijen

  • Large Portions Copyright (c) 2004-2007 Alexey Stroganov

  • Large Portions Copyright (c) 2003-2005 Rudolf Lippan

  • Large Portions Copyright (c) 1997-2003 Jochen Wiedmann, with code portions

  • Copyright (c)1994-1997 their original authors

LICENSE

This module is released under the same license as Perl itself. See Perl Licensing for details.

MAILING LIST SUPPORT

This module is maintained and supported on a mailing list, dbi-users.

To subscribe to this list, send an email to

dbi-users-subscribe@perl.org

Mailing list archives are at

http://groups.google.com/group/perl.dbi.users?hl=en&lr=

ADDITIONAL DBI INFORMATION

Additional information on the DBI project can be found on the World Wide Web at the following URL:

http://dbi.perl.org

where documentation, pointers to the mailing lists and mailing list archives and pointers to the most current versions of the modules can be used.

Information on the DBI interface itself can be gained by typing:

  perldoc DBI

Information on DBD::MariaDB specifically can be gained by typing:

  perldoc DBD::MariaDB

(this will display the document you're currently reading)

BUG REPORTING, ENHANCEMENT/FEATURE REQUESTS

Please report bugs, including all the information needed such as DBD::MariaDB version, MariaDB/MySQL version, OS type/version, etc to this link:

https://github.com/gooddata/DBD-MariaDB/issues

In past for DBD::mysql, MySQL/Sun/Oracle responded to bugs and assisted in fixing bugs which many thanks should be given for their help! This driver is outside the realm of the numerous components they support, and the maintainer and community solely support DBD::mysql and DBD::MariaDB.