Provided by: libdbd-mariadb-perl_1.21-1ubuntu2_amd64 
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 <http://backronym.fail/> and The Riddle
<https://riddle.link/> 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
<https://dev.perl.org/licenses/> 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" <mailto: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.