generate_cache_key example

        $this->terms = apply_filters_ref_array( 'terms_pre_query', array( $this->terms, &$this ) );

        if ( null !== $this->terms ) {
            return $this->terms;
        }

        $cache_key = $this->generate_cache_key( $args, $this->request );
        $cache     = wp_cache_get( $cache_key, 'term-queries' );

        if ( false !== $cache ) {
            if ( 'ids' === $_fields ) {
                $cache = array_map( 'intval', $cache );
            } elseif ( 'count' !== $_fields ) {
                if ( ( 'all_with_object_id' === $_fields && ! empty( $args['object_ids'] ) )
                    || ( 'all' === $_fields && $args['pad_counts'] )
                ) {
                    $term_ids = wp_list_pluck( $cache, 'term_id' );
                } else {
                    

$this->results = apply_filters_ref_array( 'users_pre_query', array( null, &$this ) );

        if ( null === $this->results ) {
            $this->request = " SELECT {$this->query_fields} {$this->query_from} {$this->query_where} {$this->query_orderby} {$this->query_limit} ";
            $cache_value   = false;
            $cache_key     = $this->generate_cache_key( $qv, $this->request );
            $cache_group   = 'user-queries';
            if ( $qv['cache_results'] ) {
                $cache_value = wp_cache_get( $cache_key, $cache_group );
            }
            if ( false !== $cache_value ) {
                $this->results     = $cache_value['user_data'];
                $this->total_users = $cache_value['total_users'];
            } else {

                if ( is_array( $qv['fields'] ) ) {
                    $this->results = $wpdb->get_results( $this->request );
                }

{$wpdb->posts}.*",
            "{$wpdb->posts}.ID, {$wpdb->posts}.post_parent",
            "{$wpdb->posts}.ID",
        );

        if ( ! in_array( $fields, $cacheable_field_values, true ) ) {
            $id_query_is_cacheable = false;
        }

        if ( $q['cache_results'] && $id_query_is_cacheable ) {
            $new_request = str_replace( $fields, "{$wpdb->posts}.*", $this->request );
            $cache_key   = $this->generate_cache_key( $q, $new_request );

            $cache_found = false;
            if ( null === $this->posts ) {
                $cached_results = wp_cache_get( $cache_key, 'post-queries', false, $cache_found );

                if ( $cached_results ) {
                    if ( 'ids' === $q['fields'] ) {
                        /** @var int[] */
                        $this->posts = array_map( 'intval', $cached_results['posts'] );
                    } else {
                        _prime_post_caches( $cached_results['posts'], $q['update_post_term_cache'], $q['update_post_meta_cache'] );