如何在Cosmos DB中拥有全局(跨整个容器)的唯一约束？

function createItem(item) {
    var context = getContext();
    var container = context.getCollection();
    var collectionLink = container.getSelfLink();

    // 查询是否存在相同的数据
    var query = 'SELECT * FROM c WHERE c.field = "' + item.field + '"';
    var requestOptions = { partitionKey: item.partitionKey };
    var isAccepted = container.queryDocuments(collectionLink, query, requestOptions, function (err, feed, options) {
        if (err) throw err;

        if (feed.length > 0) {
            // 存在重复数据，抛出异常
            throw new Error('Duplicate data');
        } else {
            // 不存在重复数据，插入新数据
            var isAccepted = container.createDocument(collectionLink, item, function (err, doc, options) {
                if (err) throw err;

                // 成功插入数据
                context.getResponse().setBody(doc);
            });
        }
    });
}