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20 | This can be used to make parallel sql requests using Coro, or to do other |
20 | This can be used to make parallel sql requests using Coro, or to do other |
21 | stuff while mysql is rumbling in the background. |
21 | stuff while mysql is rumbling in the background. |
22 | |
22 | |
23 | =head2 CAVEAT |
23 | =head2 CAVEAT |
24 | |
24 | |
25 | Note that this module must be linked against exactly the same |
25 | Note that this module must be linked against exactly the same (shared, |
26 | F<libmysqlclient> library as DBD::mysql, otherwise it will not work. |
26 | possibly not working with all OSes) F<libmysqlclient> library as |
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27 | DBD::mysql, otherwise it will not work. |
27 | |
28 | |
28 | Also, while this module makes database handles non-blocking, you still |
29 | Also, while this module makes database handles non-blocking, you still |
29 | cannot run multiple requests in parallel on the same database handle. If |
30 | cannot run multiple requests in parallel on the same database handle. If |
30 | you want to run multiple queries in parallel, you have to create multiple |
31 | you want to run multiple queries in parallel, you have to create multiple |
31 | database connections, one for each thread that runs queries. |
32 | database connections, one for each thread that runs queries. Not doing so |
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33 | can corrupt your data - use a Coro::Semaphore when in doubt. |
32 | |
34 | |
33 | If you make sure that you never run two or more requests in parallel, you |
35 | If you make sure that you never run two or more requests in parallel, you |
34 | cna freely share the database handles between threads, of course. |
36 | can freely share the database handles between threads, of course. |
35 | |
37 | |
36 | Also, this module uses a number of "unclean" techniques (patching an |
38 | Also, this module uses a number of "unclean" techniques (patching an |
37 | internal libmysql structure for one thing) and was hacked within a few |
39 | internal libmysql structure for one thing) and was hacked within a few |
38 | hours on a long flight to Malaysia. |
40 | hours on a long flight to Malaysia. |
39 | |
41 | |
40 | It does, however, check whether it indeed got the structure layout |
42 | It does, however, check whether it indeed got the structure layout |
41 | correct, so you should expect perl exceptions or early crashes as opposed |
43 | correct, so you should expect perl exceptions or early crashes as opposed |
42 | to data corruption when something goes wrong. |
44 | to data corruption when something goes wrong during patching. |
43 | |
45 | |
44 | =head2 SPEED |
46 | =head2 SPEED |
45 | |
47 | |
46 | This module is implemented in XS, and as long as mysqld replies quickly |
48 | This module is implemented in XS, and as long as mysqld replies quickly |
47 | enough, it adds no overhead to the standard libmysql communication |
49 | enough, it adds no overhead to the standard libmysql communication |
48 | routines (which are very badly written). |
50 | routines (which are very badly written, btw.). |
49 | |
51 | |
50 | For very fast queries ("select 0"), this module can add noticable overhead |
52 | For very fast queries ("select 0"), this module can add noticable overhead |
51 | (around 15%) as it tries to switch to other coroutines when mysqld doesn't |
53 | (around 15%) as it tries to switch to other coroutines when mysqld doesn't |
52 | deliver the data instantly. |
54 | deliver the data instantly. |
53 | |
55 | |
54 | For most types of queries, there will be no overhead, especially on |
56 | For most types of queries, there will be no extra latency, especially on |
55 | multicore systems where your perl process can do other things while mysqld |
57 | multicore systems where your perl process can do other things while mysqld |
56 | does its stuff. |
58 | does its stuff. |
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59 | |
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60 | =head2 LIMITATIONS |
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61 | |
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62 | This module only supports "standard" mysql connection handles - this |
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63 | means unix domain or TCP sockets, and excludes SSL/TLS connections, named |
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64 | pipes (windows) and shared memory (also windows). No support for these |
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65 | connection types is planned, either. |
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66 | |
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67 | =head1 FUNCTIONS |
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68 | |
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69 | Coro::Mysql offers a single user-accessible function: |
57 | |
70 | |
58 | =over 4 |
71 | =over 4 |
59 | |
72 | |
60 | =cut |
73 | =cut |
61 | |
74 | |
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75 | |
88 | |
76 | sub readable { &Coro::Handle::FH::readable } |
89 | sub readable { &Coro::Handle::FH::readable } |
77 | sub writable { &Coro::Handle::FH::writable } |
90 | sub writable { &Coro::Handle::FH::writable } |
78 | |
91 | |
79 | BEGIN { |
92 | BEGIN { |
80 | our $VERSION = '0.2'; |
93 | our $VERSION = '1.02'; |
81 | |
94 | |
82 | require XSLoader; |
95 | require XSLoader; |
83 | XSLoader::load Coro::Mysql::, $VERSION; |
96 | XSLoader::load Coro::Mysql::, $VERSION; |
84 | } |
97 | } |
85 | |
98 | |
… | |
… | |
89 | so it becomes compatible to Coro threads. |
102 | so it becomes compatible to Coro threads. |
90 | |
103 | |
91 | After that, it returns the patched handle - you should always use the |
104 | After that, it returns the patched handle - you should always use the |
92 | newly returned database handle. |
105 | newly returned database handle. |
93 | |
106 | |
94 | It is safe to call this function on any database handle, but it will only |
107 | It is safe to call this function on any database handle (or just about any |
95 | do anything to L<DBD::mysql> handles, others are returned unchanged. |
108 | value), but it will only do anything to L<DBD::mysql> handles, others are |
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109 | returned unchanged. That means it is harmless when applied to database |
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110 | handles of other databases. |
96 | |
111 | |
97 | =cut |
112 | =cut |
98 | |
113 | |
99 | sub unblock { |
114 | sub unblock { |
100 | my ($DBH) = @_; |
115 | my ($DBH) = @_; |
… | |
… | |
105 | open my $fh, "+>&" . $DBH->{sockfd} |
120 | open my $fh, "+>&" . $DBH->{sockfd} |
106 | or croak "Coro::Mysql unable to clone mysql fd"; |
121 | or croak "Coro::Mysql unable to clone mysql fd"; |
107 | |
122 | |
108 | $fh = Coro::Handle::unblock $fh; |
123 | $fh = Coro::Handle::unblock $fh; |
109 | |
124 | |
110 | _patch $sock, $DBH->{sockfd}, tied ${$fh}; |
125 | _patch $sock, $DBH->{sockfd}, $fh, tied ${$fh}; |
111 | $DBH->{private_Coro_Mysql} = guard { |
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112 | _unpatch $sock; |
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113 | undef $fh; |
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114 | }; |
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115 | } |
126 | } |
116 | |
127 | |
117 | $DBH |
128 | $DBH |
118 | } |
129 | } |
119 | |
130 | |
120 | 1; |
131 | 1; |
121 | |
132 | |
122 | =back |
133 | =back |
123 | |
134 | |
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135 | =head1 USAGE EXAMPLE |
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136 | |
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137 | This example uses L<PApp::SQL> and L<Coro::on_enter> to implement a |
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138 | function C<with_db>, that connects to a database, uses C<unblock> on the |
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139 | resulting handle and then makes sure that C<$PApp::SQL::DBH> is set to the |
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140 | (per-thread) database handle when the given thread is running (it does not |
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141 | restore any previous value of $PApp::SQL::DBH, however): |
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142 | |
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143 | use Coro; |
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144 | use Coro::Mysql; |
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145 | use PApp::SQL; |
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146 | |
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147 | sub with_db($$$&) { |
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148 | my ($database, $user, $pass, $cb) = @_; |
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149 | |
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150 | my $dbh = Coro::Mysql::unblock DBI->connect ($database, $user, $pass) |
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151 | or die $DBI::errstr; |
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152 | |
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153 | Coro::on_enter { $PApp::SQL::DBH = $dbh }; |
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154 | |
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155 | $cb->(); |
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156 | } |
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157 | |
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158 | This function makes it possible to easily use L<PApp::SQL> with |
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159 | L<Coro::Mysql>, without worrying about database handles. |
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160 | |
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161 | # now start 10 threads doing stuff |
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162 | async { |
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163 | |
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164 | with_db "DBI:mysql:test", "", "", sub { |
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165 | sql_exec "update table set col = 5 where id = 7"; |
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166 | |
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167 | my $st = sql_exec \my ($id, $name), |
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168 | "select id, name from table where name like ?", |
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169 | "a%"; |
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170 | |
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171 | while ($st->fetch) { |
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172 | ... |
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173 | } |
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174 | |
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175 | my $id = sql_insertid sql_exec "insert into table values (1,2,3)"; |
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176 | # etc. |
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177 | }; |
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178 | |
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179 | } for 1..10; |
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180 | |
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181 | =head1 SEE ALSO |
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182 | |
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183 | L<Coro>, L<PApp::SQL> (a user friendly but efficient wrapper around DBI). |
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184 | |
124 | =head1 AUTHOR |
185 | =head1 AUTHOR |
125 | |
186 | |
126 | Marc Lehmann <schmorp@schmorp.de> |
187 | Marc Lehmann <schmorp@schmorp.de> |
127 | http://home.schmorp.de/ |
188 | http://home.schmorp.de/ |
128 | |
189 | |