[英]pg client.query() does not wait at the await
我不明白为什么pg
客户端请求前面的await
在client.query()
function 内的代码之前运行后似乎无法作为代码工作。
const {Pool, Client} = require('pg')
const connectionString = 'postgressql://user@localhost:5432/database'
const client = new Client({
connectionString:connectionString
})
client.connect()
database_func()
async function database_func() {
await client.query(`SELECT t FROM es ORDER BY t DESC LIMIT 1;`, (err,res) => {
console.log('res')
return;
})
client.end()
console.log('after res')
}
我希望上面能返回这个:
=> res
=> after res
相反,它返回:
=> after res
=> res
尝试
const {Pool, Client} = require('pg')
const connectionString = 'postgressql://user@localhost:5432/database'
const client = new Client({
connectionString:connectionString
})
client.connect()
database_func();
function database_func() {
client.query(`SELECT t FROM es ORDER BY t DESC LIMIT 1;`, (err,res) => {
console.log('res')
client.end()
console.log('after res')
return;
})
}
使用 promise:
const {Pool, Client} = require('pg')
const connectionString = 'postgressql://user@localhost:5432/database'
database_func().then(() => console.log('done'))
function async database_func() {
const client = new Client({
connectionString:connectionString
});
client.connect()
await query_func(client, `SELECT t FROM es ORDER BY t DESC LIMIT 1;`);
await query_func(client, `SELECT t FROM es ORDER BY t LIMIT 1;`);
client.end()
}
function query_func(client, query) {
return new Promise((resolve, reject) => {
client.query(query, (err,res) => {
if(err) reject(err);
resolve(res);
}
});
}
看起来您正在尝试同时进行回调和异步/等待。
const {Pool, Client} = require('pg')
const connectionString = 'postgressql://user@localhost:5432/database'
const client = new Client({
connectionString:connectionString
})
client.connect()
database_func()
async function database_func() {
// You should be doing callbacks OR async/await whenever you call a query,
// You're doing both at the same time
client.query(`SELECT t FROM es ORDER BY t DESC LIMIT 1;`, (err,res) => {
console.log('res')
return;
})
// OR
let res;
try {
res = await client.query(`SELECT t FROM es ORDER BY t DESC LIMIT 1;`);
} catch (err) {
console.error(err);
}
console.log(res);
client.end();
console.log('after res')
}
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