Documentdb Sql 简明教程
DocumentDB SQL - User-Defined Functions
DocumentDB SQL 提供对用户自定义函数 (UDF) 的支持。UDF 只是另一种你可以编写的 JavaScript 函数,且它们的工作方式几乎和你预期的一样。你可以创建 UDF 以使用可以在查询中引用的自定义业务逻辑来扩展查询语言。
DocumentDB SQL 语法被扩展以使用这些 UDF 来支持自定义应用程序逻辑。UDF 可以向 DocumentDB 注册,然后被引用为 SQL 查询的一部分。
为此示例,我们考虑以下三个文档。
AndersenFamily 文档如下。
{
"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 文档如下。
{
"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 文档如下。
{
"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
}
我们来看一个我们将创建一些简单 UDF 的示例。
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其 JavaScript 代码。我们构造新 UDF 的定义对象,并使用集合的 SelfLink 和如下代码所示的 udfDefinition 对象调用 CreateUserDefinedFunctionAsync。
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 resource 属性中返回新的 UDF,并将其返回给调用者。为了显示现有的 UDF,以下是 ViewUserDefinedFunctions 的实现。我们调用 CreateUserDefinedFunctionQuery 并像往常一样遍历它们。
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 未提供用于搜索子字符串或正则表达式的内置函数,因此以下简洁的一行代码填补了缺口,它是一个 JavaScript 函数。
function udfRegEx(input, regex) {
return input.match(regex);
}
鉴于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,将第二个参数中的模式匹配字符串传递到 . match 中。我们可以运行一个子字符串查询,以在 lastName 属性中找到单词 Andersen 的所有商店。
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。就像对任何普通查询一样,我们刚刚将 SQL 传递给 CreateDocumentQuery 。最后,让我们从 CreateDocumentClient 任务中调用以上查询
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);
}
}
执行以上代码时,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