Chris M.

The Debug Bar Query Tracer plugin backtraces all calls to <code>WPDB::query()</code> and determines:
<ul>
<li>which plugin caused that database query (it ignores all queries that are a part of normal WordPress activity), and</li>
<li>the function chain that led to that query. </li>
</ul>
It then displays that information on an additional panel in the <a href="https://wordpress.org/extend/plugins/debug-bar/" rel="ugc">Debug Bar</a> 
plugin (which is required).

Debug Bar Query Tracer

A Debug Bar plugin that lets you trace what plugins are causing database queries.

Storm Consultancy

Display debug backtraces for every error generated by PHP, in addition to the standard error outputs configured for your PHP installation.
This includes E_ALL so might contain many more errors than you might expect.
This is useful for finding and debugging issues during development, but could easily break your markup, and is not for users who are not editing code directly. Requires jQuery to be included with your theme.

Development Debug Backtraces

Display debug backtraces for every error generated by PHP.

Debug Bar Query Tracer vs Development Debug Backtraces