Duplicate Queries

Question

While using the query monitor plugin I could notice I am making a database query 4 times. I am using OPP. So I have a method that gets me a list of posts by querying the database. I have to do this 4 times to allow the user to select the post. I am curious if there is any method by which I can store it and use where ever needed? So making it a single query. ( I am actually querying the list of all ACF fields)

Answer 1

Generally speaking, you could use the WP Transients API to save the query.

// Get any existing copy of our transient data
if ( false === ( $special_query_results = get_transient( 'special_query_results' ) ) ) {
    // It wasn't there, so regenerate the data and save the transient
     $special_query_results = new WP_Query( 'cat=5&order=random&tag=tech&post_meta_key=thumbnail' );
     set_transient( 'special_query_results', $special_query_results, 12 * HOUR_IN_SECONDS );
}

// Use the data like you would have normally...

This article brings up a good point by arguing that it's not a good idea to store a WP_Query() object as a transient, and instead suggests storing the post IDs returned from an expensive query in a transient, then using those IDs to create a new WP_Query. Granted, with this approach we'd be right back to having duplicate queries, but they would be lighter queries.

$cache_key = 'my-expensive-query';
if ( ! $ids = get_transient( $cache_key ) ) {
    $query = new WP_Query( array(
        'fields' => 'ids',
        // ...
    ) );

    $ids = $query->posts;
    set_transient( $cache_key, $ids, 24 * HOUR_IN_SECONDS );
}

$query = new WP_Query( array(
    'post__in' => $ids,
) );

// while ( $query->have_posts() ) ...