Avoid N+1 Queries in Post Loops

// ❌ Explicitly disabling meta cache priming, then reading meta in loop
$query = new WP_Query([
    'post_type'              => 'product',
    'posts_per_page'         => 50,
    'update_post_meta_cache' => false, // Disables bulk cache prime
]);
 
while ( $query->have_posts() ) {
    $query->the_post();
    $price = get_post_meta( get_the_ID(), '_price', true );    // Query #2
    $sku   = get_post_meta( get_the_ID(), '_sku', true );      // Query #3
    $stock = get_post_meta( get_the_ID(), '_stock', true );     // Query #4
    // × 50 posts = 150 extra queries!
    echo esc_html( "$sku: $$price ($stock in stock)" );
}
 
// ❌ get_posts() with suppress_filters disabling cache
$posts = get_posts([
    'post_type'              => 'product',
    'numberposts'            => 100,
    'update_post_meta_cache' => false,
]);
foreach ( $posts as $post ) {
    $featured_image = get_post_thumbnail_id( $post->ID ); // 1 query per post
}

// ✅ Keep update_post_meta_cache enabled (the default)
// WordPress runs one bulk query: SELECT * FROM wp_postmeta WHERE post_id IN (1,2,3,...)
$query = new WP_Query([
    'post_type'              => 'product',
    'posts_per_page'         => 50,
    'update_post_meta_cache' => true,  // Default — primes meta cache in one query
]);
 
while ( $query->have_posts() ) {
    $query->the_post();
    $price = get_post_meta( get_the_ID(), '_price', true );    // Cache hit — no query
    $sku   = get_post_meta( get_the_ID(), '_sku', true );      // Cache hit — no query
    echo esc_html( "$sku: $$price" );
}

// ✅ When you only need posts matching specific meta values, use meta_query
$query = new WP_Query([
    'post_type'      => 'product',
    'posts_per_page' => 50,
    'meta_query'     => [
        [
            'key'     => '_price',
            'value'   => 100,
            'compare' => '>=',
            'type'    => 'NUMERIC',
        ],
        [
            'key'     => '_stock',
            'value'   => 0,
            'compare' => '>',
            'type'    => 'NUMERIC',
        ],
    ],
]);

// ✅ Manually prime meta cache for a custom set of post IDs
$post_ids = [ 1, 2, 3, 4, 5 ];
update_meta_cache( 'post', $post_ids ); // One bulk query for all
 
foreach ( $post_ids as $id ) {
    $title = get_post_meta( $id, 'custom_title', true ); // All cache hits
}
 
// ✅ Disable term cache if you don't need terms (save one query)
$query = new WP_Query([
    'post_type'              => 'product',
    'posts_per_page'         => 50,
    'update_post_term_cache' => false, // Skip if not displaying categories/tags
    'no_found_rows'          => true,  // Skip SQL_CALC_FOUND_ROWS if no pagination
]);

# Find loops with meta calls that might be N+1
grep -rn "get_post_meta" wp-content/plugins/ wp-content/themes/ --include="*.php" -l | xargs grep -l "have_posts\|foreach.*\$posts"
# Find queries with disabled meta cache
grep -rn "update_post_meta_cache.*false" wp-content/ --include="*.php"