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NAME |
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Coro::Mysql - let other threads run while doing mysql requests |
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SYNOPSIS |
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use Coro::Mysql; |
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my $DBH = Coro::Mysql::unblock DBI->connect (...); |
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DESCRIPTION |
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(Note that in this manual, "thread" refers to real threads as |
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implemented by the Coro module, not to the built-in windows process |
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emulation which unfortunately is also called "threads") |
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This module "patches" DBD::mysql database handles so that they do not |
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block the whole process, but only the thread that they are used in. |
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This can be used to make parallel sql requests using Coro, or to do |
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other stuff while mysql is rumbling in the background. |
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CAVEAT |
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Note that this module must be linked against exactly the same |
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libmysqlclient library as DBD::mysql, otherwise it will not work. |
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Also, while this module makes database handles non-blocking, you still |
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cannot run multiple requests in parallel on the same database handle. If |
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you want to run multiple queries in parallel, you have to create |
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multiple database connections, one for each thread that runs queries. |
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If you make sure that you never run two or more requests in parallel, |
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you cna freely share the database handles between threads, of course. |
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Also, this module uses a number of "unclean" techniques (patching an |
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internal libmysql structure for one thing) and was hacked within a few |
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hours on a long flight to Malaysia. |
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It does, however, check whether it indeed got the structure layout |
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correct, so you should expect perl exceptions or early crashes as |
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opposed to data corruption when something goes wrong. |
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SPEED |
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This module is implemented in XS, and as long as mysqld replies quickly |
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enough, it adds no overhead to the standard libmysql communication |
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routines (which are very badly written). |
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|
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For very fast queries ("select 0"), this module can add noticable |
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overhead (around 15%) as it tries to switch to other coroutines when |
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mysqld doesn't deliver the data instantly. |
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For most types of queries, there will be no overhead, especially on |
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multicore systems where your perl process can do other things while |
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mysqld does its stuff. |
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$DBH = Coro::Mysql::unblock $DBH |
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This function takes a DBI database handles and "patches" it so it |
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becomes compatible to Coro threads. |
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After that, it returns the patched handle - you should always use |
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the newly returned database handle. |
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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