id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
22967	Null value in meta query changes the type of comparison	bradyvercher		"If a null value is set in a meta query, it effectively returns the same results as setting the 'compare' arg to 'EXISTS', even if it's explicitly set to the default '='.

For example: 

{{{
$value_var = null;
...
meta_query => array(
        array(
            'key'     => '_my_meta_key',
            'value'   => $value_var,
            'compare' => '='
        )
    )
...
}}}

That returns all rows where '_my_meta_key' exists and ignores 'value' instead of treating it like an empty string. This can be troublesome where the value is passed in dynamically like the example, so validation would have to be done prior to every meta query to ensure the value isn't null.

I've attached a patch for review that checks for the existence of the 'value' key rather than using `isset` and casts it to a string if it's null."	defect (bug)	new	normal	Awaiting Review	Query	3.5	normal		has-patch	scribu