DocumentDB SQL提供对用户定义函数(UDF)的支持. UDF只是您可以编写的另一种JavaScript函数，它们可以像您期望的那样工作.您可以使用可在查询中引用的自定义业务逻辑来创建UDF以扩展查询语言.
扩展DocumentDB SQL语法以支持使用这些UDF的自定义应用程序逻辑. UDF可以在DocumentDB中注册，然后作为SQL查询的一部分被引用.
在这个例子中，我们考虑以下三个文档.
AndersenFamily 文件如下.
{
"id": "AndersenFamily",
"lastName": "Andersen",
"parents": [
{ "firstName": "Thomas", "relationship": "father" },
{ "firstName": "Mary Kay", "relationship": "mother" }
],
"children": [
{
"firstName": "Henriette Thaulow",
"gender": "female",
"grade": 5,
"pets": [ { "givenName": "Fluffy", "type": "Rabbit" } ]
}
],
"location": { "state": "WA", "county": "King", "city": "Seattle" },
"isRegistered": true
}SmithFamily 文件如下.
{
"id": "SmithFamily",
"parents": [
{ "familyName": "Smith", "givenName": "James" },
{ "familyName": "Curtis", "givenName": "Helen" }
],
"children": [
{
"givenName": "Michelle",
"gender": "female",
"grade": 1
},
{
"givenName": "John",
"gender": "male",
"grade": 7,
"pets": [
{ "givenName": "Tweetie", "type": "Bird" }
]
}
],
"location": {
"state": "NY",
"county": "Queens",
"city": "Forest Hills"
},
"isRegistered": true
}WakefieldFamily 文件如下.
{
"id": "WakefieldFamily",
"parents": [
{ "familyName": "Wakefield", "givenName": "Robin" },
{ "familyName": "Miller", "givenName": "Ben" }
],
"children": [
{
"familyName": "Merriam",
"givenName": "Jesse",
"gender": "female",
"grade": 6,
"pets": [
{ "givenName": "Charlie Brown", "type": "Dog" },
{ "givenName": "Tiger", "type": "Cat" },
{ "givenName": "Princess", "type": "Cat" }
]
},
{
"familyName": "Miller",
"givenName": "Lisa",
"gender": "female",
"grade": 3,
"pets": [
{ "givenName": "Jake", "type": "Snake" }
]
}
],
"location": { "state": "NY", "county": "Manhattan", "city": "NY" },
"isRegistered": false
}我们来看看吧在一个例子中我们将创建一些简单的UDF.
以下是 CreateUserDefinedFunctions 的实现.
private async static Task CreateUserDefinedFunctions(DocumentClient client) {
Console.WriteLine();
Console.WriteLine("**** Create User Defined Functions ****");
Console.WriteLine();
await CreateUserDefinedFunction(client, "udfRegEx");
}我们有一个udfRegEx，在CreateUserDefinedFunction中，我们从本地文件中获取它的JavaScript代码.我们为新的UDF构造定义对象，并使用集合的SelfLink和udfDefinition对象调用CreateUserDefinedFunctionAsync，如下面的代码所示.
private async static Task<UserDefinedFunction>
CreateUserDefinedFunction(DocumentClient client, string udfId) {
var udfBody = File.ReadAllText(@"..\..\Server + udfId + ".js");
var udfDefinition = new UserDefinedFunction {
Id = udfId,
Body = udfBody
};
var result = await client
.CreateUserDefinedFunctionAsync(_collection.SelfLink, udfDefinition);
var udf = result.Resource;
Console.WriteLine("Created user defined function {0}; RID: {1}",
udf.Id, udf.ResourceId);
return udf;
}我们从结果的资源属性中获取新的UDF并将其返回给调用者.要显示现有UDF，以下是 ViewUserDefinedFunctions 的实现.我们调用 CreateUserDefinedFunctionQuery 并像往常一样循环它们.
private static void ViewUserDefinedFunctions(DocumentClient client) {
Console.WriteLine();
Console.WriteLine("**** View UDFs ****");
Console.WriteLine();
var udfs = client
.CreateUserDefinedFunctionQuery(_collection.UserDefinedFunctionsLink)
.ToList();
foreach (var udf in udfs) {
Console.WriteLine("User defined function {0}; RID: {1}", udf.Id, udf.ResourceId);
}
}DocumentDB SQL不提供内置函数来搜索子字符串或正则表达式，因此以下内容小单行填充了这个间隙，这是一个JavaScript函数.
function udfRegEx(input, regex) {
return input.match(regex);
}给定第一个参数中的输入字符串，使用JavaScript的内置正则表达式支持在第二个参数中传递模式匹配字符串进入.匹配.我们可以运行子字符串查询来查找所有在其 lastName 属性中包含Andersen一词的商店.
private static void Execute_udfRegEx(DocumentClient client) {
var sql = "SELECT c.name FROM c WHERE udf.udfRegEx(c.lastName, 'Andersen') != null";
Console.WriteLine();
Console.WriteLine("Querying for Andersen");
var documents = client.CreateDocumentQuery(_collection.SelfLink, sql).ToList();
Console.WriteLine("Found {0} Andersen:", documents.Count);
foreach (var document in documents) {
Console.WriteLine("Id: {0}, Name: {1}", document.id, document.lastName);
}
}请注意，我们必须使用前缀 udf 限定每个UDF引用.我们像任何普通的查询一样将SQL传递给 CreateDocumentQuery .最后，让我们从 CreateDocumentClient 任务调用上述查询
private static async Task CreateDocumentClient() {
// Create a new instance of the DocumentClient
using (var client = new DocumentClient(new Uri(EndpointUrl), AuthorizationKey)){
database = client.CreateDatabaseQuery("SELECT * FROM c WHERE
c.id = 'myfirstdb'").AsEnumerable().First();
collection = client.CreateDocumentCollectionQuery(database.CollectionsLink,
"SELECT * FROM c WHERE c.id = 'Families'").AsEnumerable().First();
await CreateUserDefinedFunctions(client);
ViewUserDefinedFunctions(client);
Execute_udfRegEx(client);
}
}执行上述代码时，会产生以下输出.
**** Create User Defined Functions **** Created user defined function udfRegEx; RID: kV5oANVXnwAlAAAAAAAAYA== **** View UDFs **** User defined function udfRegEx; RID: kV5oANVXnwAlAAAAAAAAYA== Querying for Andersen Found 1 Andersen: Id: AndersenFamily, Name: Andersen
