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Revision 1.2 by root, Sat May 30 06:58:22 2009 UTC vs.
Revision 1.3 by root, Sat Jul 18 05:58:27 2009 UTC

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23 23
24 Also, while this module makes database handles non-blocking, you still 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 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 26 you want to run multiple queries in parallel, you have to create
27 multiple database connections, one for each thread that runs queries. 27 multiple database connections, one for each thread that runs queries.
28 Not doing so can corrupt your data - use a Coro::Semaphore when in
29 doubt.
28 30
29 If you make sure that you never run two or more requests in parallel, 31 If you make sure that you never run two or more requests in parallel,
30 you cna freely share the database handles between threads, of course. 32 you can freely share the database handles between threads, of course.
31 33
32 Also, this module uses a number of "unclean" techniques (patching an 34 Also, this module uses a number of "unclean" techniques (patching an
33 internal libmysql structure for one thing) and was hacked within a few 35 internal libmysql structure for one thing) and was hacked within a few
34 hours on a long flight to Malaysia. 36 hours on a long flight to Malaysia.
35 37
36 It does, however, check whether it indeed got the structure layout 38 It does, however, check whether it indeed got the structure layout
37 correct, so you should expect perl exceptions or early crashes as 39 correct, so you should expect perl exceptions or early crashes as
38 opposed to data corruption when something goes wrong. 40 opposed to data corruption when something goes wrong during patching.
39 41
40 SPEED 42 SPEED
41 This module is implemented in XS, and as long as mysqld replies quickly 43 This module is implemented in XS, and as long as mysqld replies quickly
42 enough, it adds no overhead to the standard libmysql communication 44 enough, it adds no overhead to the standard libmysql communication
43 routines (which are very badly written). 45 routines (which are very badly written, btw.).
44 46
45 For very fast queries ("select 0"), this module can add noticable 47 For very fast queries ("select 0"), this module can add noticable
46 overhead (around 15%) as it tries to switch to other coroutines when 48 overhead (around 15%) as it tries to switch to other coroutines when
47 mysqld doesn't deliver the data instantly. 49 mysqld doesn't deliver the data instantly.
48 50
49 For most types of queries, there will be no overhead, especially on 51 For most types of queries, there will be no overhead, especially on
50 multicore systems where your perl process can do other things while 52 multicore systems where your perl process can do other things while
51 mysqld does its stuff. 53 mysqld does its stuff.
52 54
55 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
61FUNCTIONS
62 Coro::Mysql offers a single user-accessible function:
63
53 $DBH = Coro::Mysql::unblock $DBH 64 $DBH = Coro::Mysql::unblock $DBH
54 This function takes a DBI database handles and "patches" it so it 65 This function takes a DBI database handles and "patches" it so it
55 becomes compatible to Coro threads. 66 becomes compatible to Coro threads.
56 67
57 After that, it returns the patched handle - you should always use 68 After that, it returns the patched handle - you should always use
58 the newly returned database handle. 69 the newly returned database handle.
59 70
71 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
76USAGE 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
121SEE ALSO
122 Coro, PApp::SQL (a user friendly but efficient wrapper around DBI).
123
60AUTHOR 124AUTHOR
61 Marc Lehmann <schmorp@schmorp.de> 125 Marc Lehmann <schmorp@schmorp.de>
62 http://home.schmorp.de/ 126 http://home.schmorp.de/
63 127

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