DBD::MariaDB(3) User Contributed Perl Documentation DBD::MariaDB(3)
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.
The DBD::MariaDB driver understands any connection attribute
specified in "DATABASE HANDLES" section which is read/write and
additionally also any other attribute described below.
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
If TRUE (Default), sets the "CLIENT_FOUND_ROWS" flag when
connecting to the MariaDB or MySQL server. This causes "UPDATE"
statements to return the number of rows matched, not the number
of rows actually changed.
If you want the number of rows changed in response to an
"UPDATE" statement, specify "mariadb_client_found_rows=0" in
the DSN.
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_auth_plugin
Specify authentication method used during connection to MariaDB
or MySQL server. MySQL protocol uses "mysql_native_password"
authentication method and MySQL version 5.5.7 extended protocol
and added support for using other authentication methods which
can be provided to clients by plugins. MySQL version 8.0.4
changed the default authentication method to
"caching_sha2_password".
Example how to use "caching_sha2_password" authentication
method:
my $dsn = 'DBI:MariaDB:database=test;host=hostname;'
. 'mariadb_auth_plugin=caching_sha2_password';
mariadb_ssl
A true value enforces SSL encryption when connecting to the
MariaDB or MySQL server. A false value (which is default)
disables 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_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".
Library functions mysql_use_result() and mysql_store_result() are
not used for server side prepared statements, therefore this
mariadb_use_result attribute has no effect when server side
prepared statements are enabled.
Note that library function mysql_use_result() does not provide
number of rows in result set. Therefore if this mariadb_use_result
attribute is enabled then DBI variable $DBI::rows and statement
methods execute and rows returns -1 (which means that the number of
rows is not known). However, statement method rows returns correct
number of rows after all rows were already fetched and additional
fetch call was issued (for this special case driver knows that it
processed all rows and hence it knows what is the total number of
rows).
Enabling mariadb_use_result attribute on one statement handle
disallow usage of all other statement and database handles until
all data rows from active statement handle are fetched. Trying to
use other statement or database handles when there is active
mariadb_use_result attribute on some statement handle cause
unpredictable errors.
In most cases there is no benefit in usage of this
mariadb_use_result attribute, it should stay disabled.
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:
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:
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
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.
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:
o By default AutoCommit mode is on, following the DBI specifications.
o 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.
o 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:
o You should never change the server variable AutoCommit manually,
unless you are ignoring DBI's transaction support.
o 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!
}
o 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.
o 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.
o 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();
And another example:
my $fd = $dbh->mariadb_sockfd();
my $sth = $dbh->prepare('SELECT 1, SLEEP(10), t.id FROM t', { mariadb_async => 1 });
$sth->execute();
my $bits = '';
vec($bits, $fd, 1) = 1;
select($bits, undef, $bits, undef);
my $num_rows = $sth->mariadb_async_result();
print "num rows: $num_rows\n";
while (my @array = $sth->fetchrow_array()) {
print "row:\n";
print "\tvalue: $_\n" foreach @array;
}
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 Konig (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 Konig
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. Development at that time was supported by GoodData. Currently
it is hosted on Github as part of the big perl5-dbi project 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:
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
o Large Portions Copyright (c) 2018 GoodData Corporation
o Large Portions Copyright (c) 2015-2022 Pali Rohar
o Large Portions Copyright (c) 2004-2017 Patrick Galbraith
o Large Portions Copyright (c) 2013-2017 Michiel Beijen
o Large Portions Copyright (c) 2004-2007 Alexey Stroganov
o Large Portions Copyright (c) 2003-2005 Rudolf Lippan
o Large Portions Copyright (c) 1997-2003 Jochen Wiedmann, with code
portions
o 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
ADDITIONAL DBI INFORMATION
Additional information on the DBI project can be found on the World
Wide Web at the following URL:
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:
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.
perl v5.38.0 2023-10-24 DBD::MariaDB(3)