Source

File: wp-includes/functions.php

function is_site_meta_supported() {
	global $wpdb;

	if ( ! is_multisite() ) {
		return false;
	}

	$network_id = get_main_network_id();

	$supported = get_network_option( $network_id, 'site_meta_supported', false );
	if ( false === $supported ) {
		$supported = $wpdb->get_var( "SHOW TABLES LIKE '{$wpdb->blogmeta}'" ) ? 1 : 0;

		update_network_option( $network_id, 'site_meta_supported', $supported );
	}

	return (bool) $supported;
}