SlowDBQueryStandard.xml

<?xml version="1.0"?>
<documentation xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="https://phpcsstandards.github.io/PHPCSDevTools/phpcsdocs.xsd"
    title="Slow DB Query"
    >
    <standard>
    <![CDATA[
    Usage of the meta_query, meta_key, meta_value, and tax_query keys in array assignments and query-parameter strings is discouraged and should be carefully evaluated. When passed to WordPress database query APIs, these keys can lead to slow queries, especially on large datasets.
    ]]>
    </standard>
    <code_comparison>
        <code title="Valid: No potentially slow query keys.">
        <![CDATA[
$query = new WP_Query( array(
    'post_type' => 'post',
) );


$args = 'post_type=post&orderby=date';
        ]]>
        </code>
        <code title="Invalid: Using potentially slow query keys.">
        <![CDATA[
$query = new WP_Query( array(
    '<em>meta_key</em>'   => 'color',
    '<em>meta_value</em>' => 'blue',
) );

$args = 'post_type=post&<em>meta_key</em>=featured';
        ]]>
        </code>
    </code_comparison>
</documentation>