How to backtrace a mysql query? - php

Question

I have a large and complicated system consisting of php and javascript code, which make many mysql queries. Is there a way to 'backtrace' each mysql query to the exact line of code, which makes the query?
In mysql it is possible to trace all queries (adding a log statement to the mysql config), but it does not show which php or javascript code/module/line did the query. Is it possible to find the offending lines for each mysql query?

Answer 1

No, there is no way of MySQL knowing what line of code, class, function or file you're making a call from. It just receives a socket connection from the application running the code, and accepts input, processes it and returns a result.
All it knows about is the data it receives, and who is sending it.
You can view active connections and a brief description of what they're doing using
SHOW PROCESSLIST;
You'll get output similar to this:
Id User Host db Command Time State Info
48 test 10.0.2.2:65109 test Sleep 4621
51 test 10.0.2.2:49717 test Sleep 5
52 test 10.0.2.2:49718 test Query 0 SHOW PROCESSLIST
Generally when people want to log queries it happens somewhat similar to this
Before the query is run, log the query and any parameters
Run the query
Log the success/failure of the query, and any errors
To execute this process for systems with hundreds or thousands of queries, you'll generally find a wrapper function/class is created which accepts the appropriate parameters, processes the query as listed above, and returns the result. You could pass your wrapper method the PHP Constants __FILE__ and __LINE__ when you call it, to then log where the database call is being initiated from.
pseudo code only
// Wrapper method
function query_wrapper($stm, $file, $line)
{
log_prequery($stm, $file, $line); // Log the query, file and line
$result = $stm->execute(); // Execute the query
log_postquery($result); // Log the result (and any errors)
return $result; // Return the result
}
// In your code where you're making a database query
$db = new Database();
$stm = $db->prepare("SELECT foo FROM bar");
query_wrapper($stm, __FILE__, __LINE__);