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$log10
4.0 版的新增内容。
Amazon DocumentDB 中的$log10运算符用于计算数字以 10 为底的对数。它对于对聚合管道中的数值字段执行对数计算很有用。
参数
示例（MongoDB 外壳）
以下示例演示如何使用$log10运算符计算数值字段以 10 为底的对数。
创建示例文档
db.numbers.insertMany([
{ _id: 1, value: 1 },
{ _id: 2, value: 10 },
{ _id: 3, value: 100 },
{ _id: 4, value: 1000 }
]);
查询示例
db.numbers.aggregate([
{
$project: {
_id: 1,
log10Value: { $log10: "$value" }
}
}
]);
输出
[
{ "_id": 1, "log10Value": 0 },
{ "_id": 2, "log10Value": 1 },
{ "_id": 3, "log10Value": 2 },
{ "_id": 4, "log10Value": 3 }
]
代码示例
要查看使用该$log10命令的代码示例，请选择要使用的语言的选项卡：
- Node.js
-
const { MongoClient } = require('mongodb');
async function example() {
let client;
try {
client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
const db = client.db('test');
const collection = db.collection('numbers');
const result = await collection.aggregate([
{
$project: {
_id: 1,
log10Value: { $log10: "$value" }
}
}
]).toArray();
console.log(result);
} catch (error) {
console.error("An error occurred:", error);
} finally {
if (client) {
await client.close();
}
}
}
example();
- Python
-
from pymongo import MongoClient
def example():
client = None
try:
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client.test
collection = db.numbers
result = list(collection.aggregate([
{
'$project': {
'_id': 1,
'log10Value': { '$log10': '$value' }
}
}
]))
print(result)
except Exception as e:
print(f"An error occurred: {e}")
finally:
if client:
client.close()
example()
