Yoast SEO: Short-circuit the custom fields lookup

The wpseo_custom_fields_pre_query filter lets you bypass Yoast SEO's default SELECT DISTINCT meta_key query against the wp_postmeta table. On sites with a very large postmeta table, that query can be slow. Use this filter to supply a pre-computed or alternative list of custom field keys, and Yoast SEO will skip the database query entirely.

Parameters

Parameter	Type	Description
$custom_fields	string[]|null	Pre-computed list of meta_key names. Return null to let the default query run.
$limit	int	The configured result limit (default 30 via postmeta_form_limit). Honor it in custom queries.

When the filter returns a non-null array, Yoast SEO uses that array directly and does not run the default query.

Usage

Supplying a static list

<?php

/**
 * Supplies a hard-coded list of custom field keys, skipping the postmeta query.
 *
 * @param string[]|null $custom_fields Pre-computed list of meta_key names, or null.
 * @param int           $limit         The configured result limit.
 *
 * @return string[] The custom field keys to use.
 */
function my_custom_fields_list( $custom_fields, $limit ) {
    return [
        'my_seo_field',
        'product_sku',
        'featured_text',
    ];
}

add_filter( 'wpseo_custom_fields_pre_query', 'my_custom_fields_list', 10, 2 );

Supplying a cached list

<?php

/**
 * Returns a transient-cached list of custom field keys.
 *
 * @param string[]|null $custom_fields Pre-computed list, or null.
 * @param int           $limit         The configured result limit.
 *
 * @return string[]|null Cached list, or null to fall back to the default query.
 */
function my_cached_custom_fields( $custom_fields, $limit ) {
    $cached = get_transient( 'my_custom_field_keys' );

    if ( is_array( $cached ) ) {
        return array_slice( $cached, 0, $limit );
    }

    return null; // Fall back to Yoast SEO's own query this time.
}

add_filter( 'wpseo_custom_fields_pre_query', 'my_cached_custom_fields', 10, 2 );