我正在尝试使用定义为RANGE
键的列从DynamoDB表中获取一条记录,但是在执行此操作时出现此错误:
The provided key element does not match the schema
这是我创建和播种表的方式:
// Create words table
if(!tableExists('words')) {
console.log('Creating words table');
await createTable({
TableName: 'words',
KeySchema: [
{ AttributeName: 'id', KeyType: 'HASH' },
{ AttributeName: 'index', KeyType: 'RANGE' },
],
AttributeDefinitions: [
{ AttributeName: 'id', AttributeType: 'S' },
{ AttributeName: 'index', AttributeType: 'N' },
],
ProvisionedThroughput: { ReadCapacityUnits: 5, WriteCapacityUnits: 5 },
});
await wait(5000);
console.log('done');
} else {
console.log('words table found. Skipping.')
}
// Seed words
let index = 0;
for(let word of words) {
console.log(`Adding word ${word}`);
const params = {
TableName: tableName('words'),
Item: {
id: word,
index: index,
},
};
await db.put(params).promise();
console.log('added');
index++;
}
这是我尝试获取记录的方式:
const db = require('../db');
const getResponseItem = response => response.Item;
module.exports = function loadWordByIndex(index) {
return db.get({
TableName: 'talk_stem.words',
Key: {
index,
},
})
.promise()
.then(getResponseItem);
};
如果我什至无法在查询中引用它,定义一个RANGE
键有什么意义?
答案 0 :(得分:2)
制作get
时,您只能索取物品。获取(或不返回)与完整键相对应的单个项目,否则返回“提供的键元素与架构不匹配” 。示例:
const id = 'marmelade';
const index = 5;
db.get({
TableName: 'talk_stem.words',
Key: {
id,
index,
},
}).promise()
使用get
,您将寻找一项!
您需要的是query
(see doc here)。您可以想象这样的事情:
db.query({
TableName: 'talk_stem.words',
KeyConditionExpression: '#id = :id AND #index BETWEEN :indexLow AND :indexHigh',
ExpressionAttributeNames: {
'#id': 'id',
'#index': 'index',
},
ExpressionAttributeValues: {
':id': id, # a fixed id
':indexLow': 3,
':indexHigh': 9,
},
}).promise()
请记住,对于DynamoDB,get
和query
需要提及分区键。总是。当您想获取不知道的分区键项目时,只能执行“昂贵”的scan
。