NAME¶
DBD::mysql - MySQL driver for the Perl5 Database Interface (DBI)
SYNOPSIS¶
use DBI;
$dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
$dbh = DBI->connect($dsn, $user, $password);
$drh = DBI->install_driver("mysql");
@databases = DBI->data_sources("mysql");
or
@databases = DBI->data_sources("mysql",
{"host" => $host, "port" => $port, "user" => $user, password => $pass});
$sth = $dbh->prepare("SELECT * FROM foo WHERE bla");
or
$sth = $dbh->prepare("LISTFIELDS $table");
or
$sth = $dbh->prepare("LISTINDEX $table $index");
$sth->execute;
$numRows = $sth->rows;
$numFields = $sth->{'NUM_OF_FIELDS'};
$sth->finish;
$rc = $drh->func('createdb', $database, $host, $user, $password, 'admin');
$rc = $drh->func('dropdb', $database, $host, $user, $password, 'admin');
$rc = $drh->func('shutdown', $host, $user, $password, 'admin');
$rc = $drh->func('reload', $host, $user, $password, 'admin');
$rc = $dbh->func('createdb', $database, 'admin');
$rc = $dbh->func('dropdb', $database, 'admin');
$rc = $dbh->func('shutdown', 'admin');
$rc = $dbh->func('reload', 'admin');
EXAMPLE¶
#!/usr/bin/perl
use strict;
use DBI();
# Connect to the database.
my $dbh = DBI->connect("DBI:mysql:database=test;host=localhost",
"joe", "joe's password",
{'RaiseError' => 1});
# Drop table 'foo'. This may fail, if 'foo' doesn't exist.
# Thus we put an eval around it.
eval { $dbh->do("DROP TABLE foo") };
print "Dropping foo failed: $@\n" if $@;
# 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'. We are using $dbh->quote() for
# quoting the name.
$dbh->do("INSERT INTO foo VALUES (1, " . $dbh->quote("Tim") . ")");
# Same thing, but 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";
}
$sth->finish();
# Disconnect from the database.
$dbh->disconnect();
DESCRIPTION¶
DBD::mysql is the Perl5 Database Interface driver for the MySQL database.
In other words: DBD::mysql is an interface between the Perl programming
language and the MySQL programming API that comes with the 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::mysql, because this is what you
will need the most. For installation, see the sections on INSTALLATION, and
"WIN32 INSTALLATION" below. 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 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:
$dbh = DBI->connect("DBI:mysql:database=$db;host=$host",
$user, $password, {RaiseError => 1});
Once you have connected to a database, you can execute SQL statements with:
my $query = sprintf("INSERT INTO foo VALUES (%d, %s)",
$number, $dbh->quote("name"));
$dbh->do($query);
See DBI for details on the quote and do methods. An alternative approach is
$dbh->do("INSERT INTO foo VALUES (?, ?)", undef,
$number, $name);
in which case the quote method is executed automatically. 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:
$sth = $dbh->prepare("SELECT * FROM $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;
$dsn = "DBI:mysql:$database";
$dsn = "DBI:mysql:database=$database;host=$hostname";
$dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
$dbh = DBI->connect($dsn, $user, $password);
A "database" must always be specified.
- host
- port
- The hostname, if not specified or specified as '' or 'localhost', will
default to a MySQL server running on the local machine using the default
for the UNIX socket. To connect to a MySQL server on the local machine via
TCP, you must specify the loopback IP address (127.0.0.1) as the host.
Should the MySQL server be running on a non-standard port number, you may
explicitly state the port number to connect to in the "hostname"
argument, by concatenating the hostname and port number
together separated by a colon ( ":" ) character or by using the
"port" argument.
To connect to a MySQL server on localhost using TCP/IP, you must specify the
hostname as 127.0.0.1 (with the optional port).
- mysql_client_found_rows
- Enables (TRUE value) or disables (FALSE value) the flag CLIENT_FOUND_ROWS
while connecting to the MySQL server. This has a somewhat funny effect:
Without mysql_client_found_rows, if you perform a query like
UPDATE $table SET id = 1 WHERE id = 1
then the MySQL engine will always return 0, because no rows have changed.
With mysql_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.)
- mysql_compression
- As of MySQL 3.22.3, a new feature is supported: If your DSN contains the
option "mysql_compression=1", then the communication between
client and server will be compressed.
- mysql_connect_timeout
- If your DSN contains the option "mysql_connect_timeout=##", the
connect request to the server will timeout if it has not been successful
after the given number of seconds.
- mysql_write_timeout
- If your DSN contains the option "mysql_write_timeout=##", the
write operation to the server will timeout if it has not been successful
after the given number of seconds.
- mysql_read_timeout
- If your DSN contains the option "mysql_read_timeout=##", the
read operation to the server will timeout if it has not been successful
after the given number of seconds.
- mysql_init_command
- If your DSN contains the option "mysql_init_command=##", then
this SQL statement is executed when connecting to the MySQL server. It is
automatically re-executed if reconnection occurs.
- mysql_skip_secure_auth
- This option is for older mysql databases that don't have secure auth
set
- mysql_read_default_file
- mysql_read_default_group
- These options can be used to read a config file like /etc/my.cnf or
~/.my.cnf. By default 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
$dsn = "DBI:mysql:test;mysql_read_default_file=/home/joe/my.cnf";
$dbh = DBI->connect($dsn, $user, $password)
The option mysql_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
$dsn = "DBI:mysql:test;mysql_read_default_group=perl;"
. "mysql_read_default_file=/home/joe/my.cnf";
$dbh = DBI->connect($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.
- mysql_socket
- As of MySQL 3.21.15, it is possible to choose the Unix socket that is used
for connecting to the server. This is done, for example, with
mysql_socket=/dev/mysql
Usually there's no need for this option, unless you are using another
location for the socket than that built into the client.
- mysql_ssl
- A true value turns on the CLIENT_SSL flag when connecting to the MySQL
database:
mysql_ssl=1
This means that your communication with the server will be encrypted.
If you turn mysql_ssl on, you might also wish to use the following
flags:
- mysql_ssl_client_key
- mysql_ssl_client_cert
- mysql_ssl_ca_file
- mysql_ssl_ca_path
- mysql_ssl_cipher
- These are used to specify the respective parameters of a call to
mysql_ssl_set, if mysql_ssl is turned on.
- mysql_local_infile
- As of MySQL 3.23.49, the LOCAL capability for LOAD DATA may be disabled in
the MySQL client library by default. If your DSN contains the option
"mysql_local_infile=1", LOAD DATA LOCAL will be enabled.
(However, this option is *ineffective* if the server has also been
configured to disallow LOCAL.)
- mysql_multi_statements
- As of MySQL 4.1, 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.
- Prepared statement support (server side prepare)
- As of 3.0002_1, server side prepare statements were on by default (if your
server was >= 4.1.3). As of 3.0009, they were off by default again due
to issues with the prepared statement API (all other mysql connectors are
set this way until C API issues are resolved). The requirement to use
prepared statements still remains that you have a server >= 4.1.3
To use server side prepared statements, all you need to do is set the
variable mysql_server_prepare in the connect:
$dbh = DBI->connect(
"DBI:mysql:database=test;host=localhost;mysql_server_prepare=1",
"",
"",
{ RaiseError => 1, AutoCommit => 1 }
);
* Note: delimiter for this param is ';'
There are many benefits to using server side prepare statements, mostly if
you are performing many inserts because of that fact that a single
statement is prepared to accept multiple insert values.
To make sure that the 'make test' step tests whether server prepare works,
you just need to export the env variable MYSQL_SERVER_PREPARE:
export MYSQL_SERVER_PREPARE=1
- mysql_embedded_options
- The option <mysql_embedded_options> can be used to pass
'command-line' options to embedded server.
Example:
use DBI;
$testdsn="DBI:mysqlEmb:database=test;mysql_embedded_options=--help,--verbose";
$dbh = DBI->connect($testdsn,"a","b");
This would cause the command line help to the embedded MySQL server library
to be printed.
- mysql_embedded_groups
- The option <mysql_embedded_groups> can be used to specify the groups
in the config file( my.cnf) which will be used to get options for
embedded server. If not specified [server] and [embedded] groups will be
used.
Example:
$testdsn="DBI:mysqlEmb:database=test;mysql_embedded_groups=embedded_server,common";
- ListDBs
-
my $drh = DBI->install_driver("mysql");
@dbs = $drh->func("$hostname:$port", '_ListDBs');
@dbs = $drh->func($hostname, $port, '_ListDBs');
@dbs = $dbh->func('_ListDBs');
Returns a list of all databases managed by the MySQL server running on
$hostname, port $port. This is a legacy method. Instead, you should use
the portable method
@dbs = DBI->data_sources("mysql");
Server Administration¶
- admin
-
$rc = $drh->func("createdb", $dbname, [host, user, password,], 'admin');
$rc = $drh->func("dropdb", $dbname, [host, user, password,], 'admin');
$rc = $drh->func("shutdown", [host, user, password,], 'admin');
$rc = $drh->func("reload", [host, user, password,], 'admin');
or
$rc = $dbh->func("createdb", $dbname, 'admin');
$rc = $dbh->func("dropdb", $dbname, 'admin');
$rc = $dbh->func("shutdown", 'admin');
$rc = $dbh->func("reload", 'admin');
For server administration you need a server connection. For obtaining this
connection you have two options: Either use a driver handle (drh) and
supply the appropriate arguments (host, defaults localhost, user, defaults
to '' and password, defaults to ''). A driver handle can be obtained with
$drh = DBI->install_driver('mysql');
Otherwise reuse the existing connection of a database handle (dbh).
There's only one function available for administrative purposes, comparable
to the mysqladmin programs. The command being execute depends on the first
argument:
- createdb
- Creates the database $dbname. Equivalent to "mysqladmin create
$dbname".
- dropdb
- Drops the database $dbname. Equivalent to "mysqladmin drop
$dbname".
It should be noted that database deletion is not prompted for in any
way. Nor is it undo-able from DBI.
Once you issue the dropDB() method, the database will be gone!
These method should be used at your own risk.
- shutdown
- Silently shuts down the database engine. (Without prompting!) Equivalent
to "mysqladmin shutdown".
- reload
- Reloads the servers configuration files and/or tables. This can be
particularly important if you modify access privileges or create new
users.
DATABASE HANDLES¶
The DBD::mysql driver supports the following attributes of database handles
(read only):
$errno = $dbh->{'mysql_errno'};
$error = $dbh->{'mysql_error'};
$info = $dbh->{'mysql_hostinfo'};
$info = $dbh->{'mysql_info'};
$insertid = $dbh->{'mysql_insertid'};
$info = $dbh->{'mysql_protoinfo'};
$info = $dbh->{'mysql_serverinfo'};
$info = $dbh->{'mysql_stat'};
$threadId = $dbh->{'mysql_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() and
mysql_thread_id(), respectively.
$info_hashref = $dhb->{mysql_dbd_stats}
DBD::mysql keeps track of some statistics in the mysql_dbd_stats attribute. The
following stats are being maintained:
- auto_reconnects_ok
- The number of times that DBD::mysql successfully reconnected to the mysql
server.
- auto_reconnects_failed
- The number of times that DBD::mysql tried to reconnect to mysql but
failed.
The DBD::mysql driver also supports the following attribute(s) of database
handles (read/write):
$bool_value = $dbh->{mysql_auto_reconnect};
$dbh->{mysql_auto_reconnect} = $AutoReconnect ? 1 : 0;
- mysql_auto_reconnect
- This attribute determines whether DBD::mysql will automatically reconnect
to mysql if the connection be lost. This feature defaults to off; however,
if either the GATEWAY_INTERFACE or MOD_PERL environment variable is set,
DBD::mysql will turn mysql_auto_reconnect on. Setting mysql_auto_reconnect
to on is not advised if 'lock tables' is used because if DBD::mysql
reconnect to mysql all table locks will be lost. This attribute is ignored
when AutoCommit is turned off, and when AutoCommit is turned off,
DBD::mysql will not automatically reconnect to the server.
It is also possible to set the default value of the
"mysql_auto_reconnect" attribute for the $dbh by passing it in
the "\%attr" hash for "DBI-"connect>.
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.
- mysql_use_result
- This attribute forces the driver to use mysql_use_result rather than
mysql_store_result. 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 "mysql_use_result"
attribute for the $dbh using several ways:
- through DSN
$dbh= DBI->connect("DBI:mysql:test;mysql_use_result=1", "root", "");
- after creation of database handle
$dbh->{'mysql_use_result'}=0; #disable
$dbh->{'mysql_use_result'}=1; #enable
It is possible to set/unset the "mysql_use_result" attribute after
creation of the statement handle. See below.
- mysql_enable_utf8
- This attribute determines whether DBD::mysql should assume strings stored
in the database are utf8. This feature defaults to off.
When set, a data retrieved from a textual column type (char, varchar, etc)
will have the UTF-8 flag turned on if necessary. This enables character
semantics on that string. You will also need to ensure that your database
/ table / column is configured to use UTF8. See Chapter 10 of the mysql
manual for details.
Additionally, turning on this flag tells MySQL that incoming data should be
treated as UTF-8. This will only take effect if used as part of the call
to connect(). If you turn the flag on after connecting, you will
need to issue the command "SET NAMES utf8" to get the same
effect.
This option is experimental and may change in future versions.
- mysql_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. This was previously called
"unsafe_bind_type_guessing" because it is experimental. I have
successfully run the full test suite with this option turned on, the name
can now be simply "mysql_bind_type_guessing".
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/Ticket/Display.html?id=43822
"mysql_bind_type_guessing" can be turned on via
- through DSN
my $dbh= DBI->connect('DBI:mysql:test', 'username', 'pass',
{ mysql_bind_type_guessing => 1})
- OR after handle creation
$dbh->{mysql_bind_type_guessing} = 1;
- mysql_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, so I have made it available in 4.015
- mysql_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
"mysql_no_autocommit_cmd" can be turned on via
- through DSN
my $dbh= DBI->connect('DBI:mysql:test', 'username', 'pass',
{ mysql_no_autocommit_cmd => 1})
- OR after handle creation
$dbh->{mysql_no_autocommit_cmd} = 1;
STATEMENT HANDLES¶
The statement handles of DBD::mysql 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 in that case. The most important
exception is the "mysql_use_result" attribute: This forces the
driver to use mysql_use_result rather than mysql_store_result. The former is
faster and less memory consuming, but tends to block other processes. (That's
why mysql_store_result is the default.)
To set the "mysql_use_result" attribute, use either of the following:
my $sth = $dbh->prepare("QUERY", { "mysql_use_result" => 1});
or
my $sth = $dbh->prepare("QUERY");
$sth->{"mysql_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 $table");
if (!$sth) {
die "Error:" . $dbh->errstr . "\n";
}
if (!$sth->execute) {
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::mysql. 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 max_length attribute.
- mysql_insertid
- MySQL has the ability to choose unique key values automatically. If this
happened, the new ID will be stored in this attribute. An alternative way
for accessing this attribute is via $dbh->{'mysql_insertid'}. (Note we
are using the $dbh in this case!)
- mysql_is_blob
- Reference to an array of boolean values; TRUE indicates, that the
respective column is a blob. This attribute is valid for MySQL only.
- mysql_is_key
- Reference to an array of boolean values; TRUE indicates, that the
respective column is a key. This is valid for MySQL only.
- mysql_is_num
- Reference to an array of boolean values; TRUE indicates, that the
respective column contains numeric values.
- mysql_is_pri_key
- Reference to an array of boolean values; TRUE indicates, that the
respective column is a primary key.
- mysql_is_auto_increment
- Reference to an array of boolean values; TRUE indicates that the
respective column is an AUTO_INCREMENT column. This is only valid for
MySQL.
- mysql_length
- mysql_max_length
- A reference to an array of maximum column sizes. The max_length is
the maximum physically present in the result table, length gives
the theoretically possible maximum. max_length is valid for MySQL
only.
- mysql_clientinfo
- List information of the MySQL client library that DBD::mysql was built
against:
print "$dbh->{mysql_clientinfo}\n";
5.2.0-MariaDB
- mysql_clientversion
- print "$dbh->{mysql_clientversion}\n";
50200
- mysql_serverversion
- print "$dbh->{mysql_serverversion}\n";
50200
- NAME
- A reference to an array of column names.
- NULLABLE
- A reference to an array of boolean values; TRUE indicates that this column
may contain NULL's.
- NUM_OF_FIELDS
- Number of fields returned by a SELECT or LISTFIELDS
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.
- mysql_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, for example DBD::mysql::FIELD_TYPE_INTERVAL is
mapped to DBI::SQL_VARCHAR(). If you need the native column types,
use mysql_type. See below.
- mysql_type
- A reference to an array of MySQL's native column types, for example
DBD::mysql::FIELD_TYPE_SHORT() or
DBD::mysql::FIELD_TYPE_STRING(). Use the TYPE attribute, if
you want portable types like DBI::SQL_SMALLINT() or
DBI::SQL_VARCHAR().
- mysql_type_name
- Similar to mysql, but type names and not numbers are returned. Whenever
possible, the ANSI SQL name is preferred.
- mysql_warning_count
- The number of warnings generated during execution of the SQL statement.
This attribute is available on both statement handles and database
handles.
TRANSACTION SUPPORT¶
Beginning with DBD::mysql 2.0416, transactions are supported. 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 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 COMMIT and ROLLBACK, 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::mysql 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::mysql can be toggled by using
the mysql_auto_reconnect attribute. This behaviour should be turned off in
code that uses LOCK TABLE because if the database server time out and
DBD::mysql reconnect, table locks will be lost without any indication of
such loss.
MULTIPLE RESULT SETS¶
As of version 3.0002_5, DBD::mysql supports multiple result sets (Thanks to Guy
Harrison!). This is the first release of this functionality, so there may be
issues. Please report bugs if you run into them!
The basic usage of multiple result sets is
do
{
while (@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 print $DBI::errstr;
$sth=$dbh->prepare('call someproc()') ||
die $DBI::err.": ".$DBI::errstr;
$sth->execute || die DBI::err.": ".$DBI::errstr; $rowset=0;
do {
print "\nRowset ".++$i."\n---------------------------------------\n\n";
foreach $colno (0..$sth->{NUM_OF_FIELDS}-1) {
print $sth->{NAME}->[$colno]."\t";
}
print "\n";
while (@row= $sth->fetchrow_array()) {
foreach $field (0..$#row) {
print $row[$field]."\t";
}
print "\n";
}
} until (!$sth->more_results)
For more examples, please see the eg/ directory. This is where helpful
DBD::mysql code snippets will be added in the future.
Issues with Multiple result sets¶
So far, the main issue is 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. This is something that will be fixed soon.
MULTITHREADING¶
The multithreading capabilities of DBD::mysql 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::mysql 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 "mostly" and, in theory, you should be able to get a
"yes", if the C library is compiled for being thread safe (By
default it isn't.) by passing the option -with-thread-safe-client to
configure. See the section on
How to make a threadsafe client in the
manual.
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
'async' attribute to a true value in the "do" in DBI method, or in
the "prepare" in DBI method. Statements created with 'async' set to
true in prepare always run their queries asynchronously when
"execute" in DBI is called. The driver also offers three additional
methods: "mysql_async_result", "mysql_async_ready", and
"mysql_fd". "mysql_async_result" returns what do or
execute would have; that is, the number of rows affected.
"mysql_async_ready" returns true if "mysql_async_result"
will not block, and zero otherwise. They both return "undef" if that
handle is not currently running an asynchronous query. "mysql_fd"
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';
$dbh->do('SELECT SLEEP(10)', { async => 1 });
until($dbh->mysql_async_ready) {
say 'not ready yet!';
sleep 1;
}
my $rows = $dbh->mysql_async_result;
INSTALLATION¶
Windows users may skip this section and pass over to WIN32 INSTALLATION below.
Others, go on reading.
Environment Variables¶
For ease of use, you can now set environment variables for DBD::mysql
installation. You can set any or all of the options, and export them by
putting them in your .bashrc or the like:
export DBD_MYSQL_CFLAGS=-I/usr/local/mysql/include/mysql
export DBD_MYSQL_LIBS="-L/usr/local/mysql/lib/mysql -lmysqlclient"
export DBD_MYSQL_EMBEDDED=
export DBD_MYSQL_CONFIG=mysql_config
export DBD_MYSQL_NOCATCHSTDERR=0
export DBD_MYSQL_NOFOUNDROWS=0
export DBD_MYSQL_SSL=
export DBD_MYSQL_TESTDB=test
export DBD_MYSQL_TESTHOST=localhost
export DBD_MYSQL_TESTPASSWORD=s3kr1+
export DBD_MYSQL_TESTPORT=3306
export DBD_MYSQL_TESTUSER=me
The most useful may be the host, database, port, socket, user, and password.
Installation will first look to your mysql_config, and then your environment
variables, and then it will guess with intelligent defaults.
Installing with CPAN¶
First of all, you do not need an installed MySQL server for installing
DBD::mysql. However, you need at least the client libraries and possibly the
header files, if you are compiling DBD::mysql from source. In the case of
MySQL you can create a client-only version by using the configure option
--without-server. If you are using precompiled binaries, then it may be
possible to use just selected RPM's like MySQL-client and MySQL-devel or
something similar, depending on the distribution.
I recommend trying automatic installation via the CPAN module. Try
cpan
If you are using the CPAN module for the first time, it will prompt you a lot of
questions. If you finally receive the CPAN prompt, enter
install DBD::mysql
Manual Installation¶
If this fails (which may be the case for a number of reasons, for example
because you are behind a firewall or don't have network access), you need to
do a manual installation. First of all you need to fetch the modules from CPAN
L<https://metacpan.org>
The following modules are required
DBI
DBD::mysql
Then enter the following commands (note - versions are just examples):
gzip -cd DBI-(version).tar.gz | tar xf -
cd DBI-(version)
perl Makefile.PL
make
make test
make install
cd ..
gzip -cd DBD-mysql-(version)-tar.gz | tar xf -
cd DBD-mysql-(version)
perl Makefile.PL
make
make test
make install
During "perl Makefile.PL" you will be prompted some questions. Other
questions are the directories with header files and libraries. For example, of
your file
mysql.h is in
/usr/include/mysql/mysql.h, then enter
the header directory
/usr, likewise for
/usr/lib/mysql/libmysqlclient.a or
/usr/lib/libmysqlclient.so.
MARIADB NATIVE CLIENT INSTALLATION¶
The MariaDB native client is another option for connecting to a MySQL database
licensed LGPL 2.1. To build DBD::mysql against this client, you will first
need to build the client. Generally, this is done with the following:
cd path/to/src/mariadb-native-client
cmake -G "Unix Makefiles'
make
sudo make install
Once the client is built and installed, you can build DBD::mysql against it:
perl Makefile.PL --testuser=xxx --testpassword=xxx --testsocket=/path/to//mysqld.sock --mysql_config=/usr/local/bin/mariadb_config
make
make test
make install
WIN32 INSTALLATION¶
If you are using ActivePerl, you may use ppm to install DBD-mysql.
ppm install DBI
ppm install DBD::mysql
If you need an HTTP proxy, you might need to set the environment variable
http_proxy, for example like this:
set http_proxy=http://myproxy.com:8080/
I recommend using the win32clients package for installing DBD::mysql under
Win32, available for download on www.tcx.se. The following steps have been
required for me:
- -
- Extract sources into C:\. This will create a directory
C:\mysql with subdirectories include and lib.
IMPORTANT: Make sure this subdirectory is not shared by other TCX files! In
particular do *not* store the MySQL server in the same directory. If the
server is already installed in C:\mysql, choose a location like
C:\tmp, extract the win32clients there. Note that you can remove
this directory entirely once you have installed DBD::mysql.
- -
- Extract the DBD::mysql sources into another directory, for example
C:\src\siteperl
- -
- Open a CMD.exe shell and change directory to C:\src\siteperl.
- -
- The next step is only required if you repeat building the modules: Make
sure that you have a clean build tree by running
nmake realclean
If you don't have VC++, replace nmake with your flavor of make. If error
messages are reported in this step, you may safely ignore them.
- -
- Run
perl Makefile.PL
which will prompt you for some settings. The really important ones are:
Which DBMS do you want to use?
enter a 1 here (MySQL only), and
Where is your mysql installed? Please tell me the directory that
contains the subdir include.
where you have to enter the win32clients directory, for example
C:\mysql or C:\tmp\mysql.
- -
- Continued in the usual way:
nmake
nmake 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 Koenig <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 Koenig 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).
For the past nine years DBD::mysql has been maintained by Patrick Galbraith (
patg@patg.net), and recently 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
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/perl5-dbi/DBD-mysql/>
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::mysql have come from the community.
COPYRIGHT¶
This module is
- •
- Large Portions Copyright (c) 2004-2013 Patrick Galbraith
- •
- Large Portions Copyright (c) 2004-2006 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
<
http://www.perl.com/perl/misc/Artistic.html> for details.
MAILING LIST SUPPORT¶
This module is maintained and supported on a mailing list, dbi-users.
To subscribe to this list, send an email to
dbi-users-subscribe@perl.org
Mailing list archives are at
<
http://groups.google.com/group/perl.dbi.users?hl=en&lr=>
Additional 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::mysql specifically can be gained by typing:
perldoc DBD::mysql
(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::mysql
version, MySQL version, OS type/version, etc to this link:
<
https://rt.cpan.org/Dist/Display.html?Name=DBD-mysql>
Note: until recently, 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