Source

File: wp-includes/class-wp-comment-query.php

public function get_comments() {
		global $wpdb;

		$this->parse_query();

		// Parse meta query.
		$this->meta_query = new WP_Meta_Query();
		$this->meta_query->parse_query_vars( $this->query_vars );

		/**
		 * Fires before comments are retrieved.
		 *
		 * @since 3.1.0
		 *
		 * @param WP_Comment_Query $this Current instance of WP_Comment_Query (passed by reference).
		 */
		do_action_ref_array( 'pre_get_comments', array( &$this ) );

		// Reparse query vars, in case they were modified in a 'pre_get_comments' callback.
		$this->meta_query->parse_query_vars( $this->query_vars );
		if ( ! empty( $this->meta_query->queries ) ) {
			$this->meta_query_clauses = $this->meta_query->get_sql( 'comment', $wpdb->comments, 'comment_ID', $this );
		}

		$comment_data = null;

		/**
		 * Filter the comments data before the query takes place.
		 *
		 * Return a non-null value to bypass WordPress's default comment queries.
		 *
		 * The expected return type from this filter depends on the value passed in the request query_vars.
		 * When `$this->query_vars['count']` is set, the filter should return the comment count as an int.
		 * When `'ids' === $this->query_vars['fields']`, the filter should return an array of comment IDs.
		 * Otherwise the filter should return an array of WP_Comment objects.
		 *
		 * @since 5.3.0
		 *
		 * @param array|int|null   $comment_data Return an array of comment data to short-circuit WP's comment query,
		 *                                       the comment count as an integer if `$this->query_vars['count']` is set,
		 *                                       or null to allow WP to run its normal queries.
		 * @param WP_Comment_Query $this         The WP_Comment_Query instance, passed by reference.
		 */
		$comment_data = apply_filters_ref_array( 'comments_pre_query', array( $comment_data, &$this ) );

		if ( null !== $comment_data ) {
			return $comment_data;
		}

		/*
		 * Only use the args defined in the query_var_defaults to compute the key,
		 * but ignore 'fields', which does not affect query results.
		 */
		$_args = wp_array_slice_assoc( $this->query_vars, array_keys( $this->query_var_defaults ) );
		unset( $_args['fields'] );

		$key          = md5( serialize( $_args ) );
		$last_changed = wp_cache_get_last_changed( 'comment' );

		$cache_key   = "get_comments:$key:$last_changed";
		$cache_value = wp_cache_get( $cache_key, 'comment' );
		if ( false === $cache_value ) {
			$comment_ids = $this->get_comment_ids();
			if ( $comment_ids ) {
				$this->set_found_comments();
			}

			$cache_value = array(
				'comment_ids'    => $comment_ids,
				'found_comments' => $this->found_comments,
			);
			wp_cache_add( $cache_key, $cache_value, 'comment' );
		} else {
			$comment_ids          = $cache_value['comment_ids'];
			$this->found_comments = $cache_value['found_comments'];
		}

		if ( $this->found_comments && $this->query_vars['number'] ) {
			$this->max_num_pages = ceil( $this->found_comments / $this->query_vars['number'] );
		}

		// If querying for a count only, there's nothing more to do.
		if ( $this->query_vars['count'] ) {
			// $comment_ids is actually a count in this case.
			return intval( $comment_ids );
		}

		$comment_ids = array_map( 'intval', $comment_ids );

		if ( 'ids' === $this->query_vars['fields'] ) {
			$this->comments = $comment_ids;
			return $this->comments;
		}

		_prime_comment_caches( $comment_ids, $this->query_vars['update_comment_meta_cache'] );

		// Fetch full comment objects from the primed cache.
		$_comments = array();
		foreach ( $comment_ids as $comment_id ) {
			$_comment = get_comment( $comment_id );
			if ( $_comment ) {
				$_comments[] = $_comment;
			}
		}

		// Prime comment post caches.
		if ( $this->query_vars['update_comment_post_cache'] ) {
			$comment_post_ids = array();
			foreach ( $_comments as $_comment ) {
				$comment_post_ids[] = $_comment->comment_post_ID;
			}

			_prime_post_caches( $comment_post_ids, false, false );
		}

		/**
		 * Filters the comment query results.
		 *
		 * @since 3.1.0
		 *
		 * @param WP_Comment[]     $_comments An array of comments.
		 * @param WP_Comment_Query $this      Current instance of WP_Comment_Query (passed by reference).
		 */
		$_comments = apply_filters_ref_array( 'the_comments', array( $_comments, &$this ) );

		// Convert to WP_Comment instances.
		$comments = array_map( 'get_comment', $_comments );

		if ( $this->query_vars['hierarchical'] ) {
			$comments = $this->fill_descendants( $comments );
		}

		$this->comments = $comments;
		return $this->comments;
	}