node.js Knex 事务与承诺
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Knex Transaction with Promises
提问by david
I am getting the correct output, and indeed, these two operations are being treated as a single transactional unit; where if one fails, both fail.
我得到了正确的输出，实际上，这两个操作被视为一个事务单元；如果一个失败，两个都失败。
In this code example: i am doing a transaction of
在这个代码示例中：我正在做一个交易
(1) insert (2) update
(1) 插入 (2) 更新
The way I approach it is to nest my db operations inside the .then. My question is if this code is correct by accident? i am new to promises and knex.
我处理它的方法是将我的数据库操作嵌套在 .then 中。我的问题是这段代码是否偶然正确？我是 promises 和 knex 的新手。
knex.transaction(function(t) {
knex('foo')
.transacting(t)
.insert({id:"asdfk", username:"barry", email:"[email protected]"})
.then(function() {
knex('foo')
.where('username','=','bob')
.update({email:"[email protected]"})
.then(t.commit, t.rollback)
})
})
.then(function() {
// it worked
},
function() {
// it failed
});
This works, but I feel like I am doing something wrong still. Looking for comments.
这有效，但我觉得我仍然做错了什么。寻找评论。
回答by Esailija
You need to return a promise from the inner query in order for the outer chain to be chained with that.
您需要从内部查询返回一个承诺，以便将外部链与它链接起来。
You also swallow any errors because you don't rethrow them - it's better to use .catch()for this reason because it makes it more clearer what is happening - that is what would happen with normal try-catchstatement.
您还可以吞下任何错误，因为您不会重新抛出它们 -.catch()出于这个原因，最好使用它，因为它可以更清楚地了解正在发生的事情 - 这就是正常try-catch语句会发生的情况。
knex.transaction(function(t) {
return knex('foo')
.transacting(t)
.insert({id:"asdfk", username:"barry", email:"[email protected]"})
.then(function() {
return knex('foo')
.where('username','=','bob')
.update({email:"[email protected]"});
})
.then(t.commit)
.catch(function(e) {
t.rollback();
throw e;
})
})
.then(function() {
// it worked
})
.catch(function(e) {
// it failed
});
To understand it better, here's the synchronous version that is being "emulated":
为了更好地理解它，这里是“模拟”的同步版本：
try {
var t = knex.transaction();
try {
knex("foo")
.transacting(t)
.insert({id:"asdfk", username:"barry", email:"[email protected]"});
knex("foo")
.where('username','=','bob')
.update({email:"[email protected]"});
t.commit();
}
catch (e) {
t.rollback();
// As you can see, if you don't rethrow here
// the outer catch is never triggered
throw e;
}
// It worked
}
catch (e) {
//It failed
}
