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$rtrim
4.0 版的新增内容。
弹性集群不支持。
Amazon DocumentDB 中的$rtrim运算符用于从字符串中删除尾随字符。默认情况下，它会删除尾随的空格字符，但您也可以通过传递 chars 参数来指定一组要删除的字符。
参数
示例（MongoDB 外壳）
以下示例演示如何使用$rtrim运算符从字符串中删除尾随的指定字符 (” *”)。
创建示例文档
db.collection.insert([
{ "name": "John Doe* ", "age": 30 },
{ "name": "Jane Smith ", "age": 25 },
{ "name": "Bob Johnson", "age": 35 }
]);
查询示例
db.collection.aggregate([
{
$project: {
_id: 0,
name: { $rtrim: { input: "$name", chars: " *" } },
age: 1
}
}
]);
输出
[
{ age: 30, name: 'John Doe' },
{ age: 25, name: 'Jane Smith' },
{ age: 35, name: 'Bob Johnson' }
]
代码示例
要查看使用该$rtrim命令的代码示例，请选择要使用的语言的选项卡：
- Node.js
-
const { MongoClient, Bson } = require('mongodb');
async function example() {
const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
try {
const db = client.db('test');
const collection = db.collection('collection');
const pipeline = [
{
$project: {
_id: 0,
name: { $rtrim: { input: "$name", chars: " *" } },
age: 1
}
}
];
const results = await collection.aggregate(pipeline).toArray();
console.dir(results, { depth: null });
} catch (err) {
console.error('Error occurred:', err);
} finally {
await client.close();
}
}
example().catch(console.error);
- Python
-
from pymongo import MongoClient
def example():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
try:
db = client.test
collection = db.collection
pipeline = [
{
"$project": {
"_id": 0,
"name": { "$rtrim": { "input": "$name", "chars": " *" } },
"age": 1
}
}
]
results = collection.aggregate(pipeline)
for doc in results:
print(doc)
except Exception as e:
print(f"An error occurred: {e}")
finally:
client.close()
example()
