[ViewVC] Annotation of: cvs/Coro-Mysql/README

NAME
    Coro::Mysql - let other threads run while doing mysql requests

SYNOPSIS
     use Coro::Mysql;

     my $DBH = Coro::Mysql::unblock DBI->connect (...);

DESCRIPTION
    (Note that in this manual, "thread" refers to real threads as
    implemented by the Coro module, not to the built-in windows process
    emulation which unfortunately is also called "threads")

    This module "patches" DBD::mysql database handles so that they do not
    block the whole process, but only the thread that they are used in.

    This can be used to make parallel sql requests using Coro, or to do
    other stuff while mysql is rumbling in the background.

  CAVEAT
    Note that this module must be linked against exactly the same
    libmysqlclient library as DBD::mysql, otherwise it will not work.

    Also, while this module makes database handles non-blocking, you still
    cannot run multiple requests in parallel on the same database handle. If
    you want to run multiple queries in parallel, you have to create
    multiple database connections, one for each thread that runs queries.
    Not doing so can corrupt your data - use a Coro::Semaphore when in
    doubt.

    If you make sure that you never run two or more requests in parallel,
    you can freely share the database handles between threads, of course.

    Also, this module uses a number of "unclean" techniques (patching an
    internal libmysql structure for one thing) and was hacked within a few
    hours on a long flight to Malaysia.

    It does, however, check whether it indeed got the structure layout
    correct, so you should expect perl exceptions or early crashes as
    opposed to data corruption when something goes wrong during patching.

  SPEED
    This module is implemented in XS, and as long as mysqld replies quickly
    enough, it adds no overhead to the standard libmysql communication
    routines (which are very badly written, btw.).

    For very fast queries ("select 0"), this module can add noticable
    overhead (around 15%) as it tries to switch to other coroutines when
    mysqld doesn't deliver the data instantly.

    For most types of queries, there will be no overhead, especially on
    multicore systems where your perl process can do other things while
    mysqld does its stuff.

  LIMITATIONS
    This module only supports "standard" mysql connection handles - this
    means unix domain or TCP sockets, and excludes SSL/TLS connections,
    named pipes (windows) and shared memory (also windows). No support for
    these connection types is planned, either.

FUNCTIONS
    Coro::Mysql offers a single user-accessible function:

    $DBH = Coro::Mysql::unblock $DBH
        This function takes a DBI database handles and "patches" it so it
        becomes compatible to Coro threads.

        After that, it returns the patched handle - you should always use
        the newly returned database handle.

        It is safe to call this function on any database handle (or just
        about any value), but it will only do anything to DBD::mysql
        handles, others are returned unchanged. That means it is harmless
        when applied to database handles of other databases.

USAGE EXAMPLE
    This example uses PApp::SQL and Coro::on_enter to implement a function
    "with_db", that connects to a database, uses "unblock" on the resulting
    handle and then makes sure that $PApp::SQL::DBH is set to the
    (per-thread) database handle when the given thread is running (it does
    not restore any previous value of $PApp::SQL::DBH, however):

       use Coro;
       use Coro::Mysql;
       use PApp::SQL;

       sub with_db($$$&) {
          my ($database, $user, $pass, $cb) = @_;

          my $dbh = Coro::Mysql::unblock DBI->connect ($database, $user, $pass)
             or die $DBI::errstr;

          Coro::on_enter { $PApp::SQL::DBH = $dbh };

          $cb->();
       }

    This function makes it possible to easily use PApp::SQL with
    Coro::Mysql, without worrying about database handles.

       # now start 10 threads doing stuff
       async {

          with_db "DBI:mysql:test", "", "", sub {
             sql_exec "update table set col = 5 where id = 7";

             my $st = sql_exec \my ($id, $name),
                               "select id, name from table where name like ?",
                               "a%";

             while ($st->fetch) {
                ...
             }

             my $id = sql_insertid sql_exec "insert into table values (1,2,3)";
             # etc.
          };

       } for 1..10;

SEE ALSO
    Coro, PApp::SQL (a user friendly but efficient wrapper around DBI).

AUTHOR
     Marc Lehmann <schmorp@schmorp.de>
     http://home.schmorp.de/

Revision:	1.3
Committed:	Sat Jul 18 05:58:27 2009 UTC (14 years, 11 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_02, rel-1_01
Changes since 1.2:	+67 -3 lines
Log Message:	riddify us of meta.yml garbage in manifest
#	User	Rev	Content
1	root	1.2	NAME
2			Coro::Mysql - let other threads run while doing mysql requests
3
4			SYNOPSIS
5			use Coro::Mysql;
6
7			my $DBH = Coro::Mysql::unblock DBI->connect (...);
8
9			DESCRIPTION
10			(Note that in this manual, "thread" refers to real threads as
11			implemented by the Coro module, not to the built-in windows process
12			emulation which unfortunately is also called "threads")
13
14			This module "patches" DBD::mysql database handles so that they do not
15			block the whole process, but only the thread that they are used in.
16
17			This can be used to make parallel sql requests using Coro, or to do
18			other stuff while mysql is rumbling in the background.
19
20			CAVEAT
21			Note that this module must be linked against exactly the same
22			libmysqlclient library as DBD::mysql, otherwise it will not work.
23
24			Also, while this module makes database handles non-blocking, you still
25			cannot run multiple requests in parallel on the same database handle. If
26			you want to run multiple queries in parallel, you have to create
27			multiple database connections, one for each thread that runs queries.
28	root	1.3	Not doing so can corrupt your data - use a Coro::Semaphore when in
29			doubt.
30	root	1.2
31			If you make sure that you never run two or more requests in parallel,
32	root	1.3	you can freely share the database handles between threads, of course.
33	root	1.2
34			Also, this module uses a number of "unclean" techniques (patching an
35			internal libmysql structure for one thing) and was hacked within a few
36			hours on a long flight to Malaysia.
37
38			It does, however, check whether it indeed got the structure layout
39			correct, so you should expect perl exceptions or early crashes as
40	root	1.3	opposed to data corruption when something goes wrong during patching.
41	root	1.2
42			SPEED
43			This module is implemented in XS, and as long as mysqld replies quickly
44			enough, it adds no overhead to the standard libmysql communication
45	root	1.3	routines (which are very badly written, btw.).
46	root	1.2
47			For very fast queries ("select 0"), this module can add noticable
48			overhead (around 15%) as it tries to switch to other coroutines when
49			mysqld doesn't deliver the data instantly.
50
51			For most types of queries, there will be no overhead, especially on
52			multicore systems where your perl process can do other things while
53			mysqld does its stuff.
54
55	root	1.3	LIMITATIONS
56			This module only supports "standard" mysql connection handles - this
57			means unix domain or TCP sockets, and excludes SSL/TLS connections,
58			named pipes (windows) and shared memory (also windows). No support for
59			these connection types is planned, either.
60
61			FUNCTIONS
62			Coro::Mysql offers a single user-accessible function:
63
64	root	1.2	$DBH = Coro::Mysql::unblock $DBH
65			This function takes a DBI database handles and "patches" it so it
66			becomes compatible to Coro threads.
67
68			After that, it returns the patched handle - you should always use
69			the newly returned database handle.
70
71	root	1.3	It is safe to call this function on any database handle (or just
72			about any value), but it will only do anything to DBD::mysql
73			handles, others are returned unchanged. That means it is harmless
74			when applied to database handles of other databases.
75
76			USAGE EXAMPLE
77			This example uses PApp::SQL and Coro::on_enter to implement a function
78			"with_db", that connects to a database, uses "unblock" on the resulting
79			handle and then makes sure that $PApp::SQL::DBH is set to the
80			(per-thread) database handle when the given thread is running (it does
81			not restore any previous value of $PApp::SQL::DBH, however):
82
83			use Coro;
84			use Coro::Mysql;
85			use PApp::SQL;
86
87			sub with_db($$$&) {
88			my ($database, $user, $pass, $cb) = @_;
89
90			my $dbh = Coro::Mysql::unblock DBI->connect ($database, $user, $pass)
91			or die $DBI::errstr;
92
93			Coro::on_enter { $PApp::SQL::DBH = $dbh };
94
95			$cb->();
96			}
97
98			This function makes it possible to easily use PApp::SQL with
99			Coro::Mysql, without worrying about database handles.
100
101			# now start 10 threads doing stuff
102			async {
103
104			with_db "DBI:mysql:test", "", "", sub {
105			sql_exec "update table set col = 5 where id = 7";
106
107			my $st = sql_exec \my ($id, $name),
108			"select id, name from table where name like ?",
109			"a%";
110
111			while ($st->fetch) {
112			...
113			}
114
115			my $id = sql_insertid sql_exec "insert into table values (1,2,3)";
116			# etc.
117			};
118
119			} for 1..10;
120
121			SEE ALSO
122			Coro, PApp::SQL (a user friendly but efficient wrapper around DBI).
123
124	root	1.2	AUTHOR
125			Marc Lehmann <schmorp@schmorp.de>
126			http://home.schmorp.de/
127