我正在形成要在aggregate()中执行的查询,如下所示:
query.$project = {};
query.$project.created_at = '$created_at';
query.$project.month = {};
query.$project.month.$month = currentMonth;
query.$match = {};
query.$match.month = currentMonth.getMonth() + 1;
query.$limit = 5;
query.$sort = {};
query.$sort.created_at = -1;
query.callback = function(err, result){
// do something
};
console.dir(query);
但是当我执行以下内容时:
DataTable.aggregate(query);
我明白了:
Error: Arguments must be aggregate pipeline operators
at Aggregate.append (C:\myproject\node_modules\mongoose\lib\aggregate.js:87:11)
at new Aggregate (C:\myproject\node_modules\mongoose\lib\aggregate.js:47:17)
at Function.aggregate (C:\myproject\node_modules\mongoose\lib\model.js:1889:17)
at C:\myproject\app\routes.js:179:23
at C:\myproject\node_modules\async\lib\async.js:570:21
at C:\myproject\node_modules\async\lib\async.js:249:17
at C:\myproject\node_modules\async\lib\async.js:125:13
我现在有两个问题:
我修改了上面的代码如下:
query.$project = {};
query.$project.created_at = '$created_at';
query.$project.month = {};
query.$project.month.$month = currentMonth;
query.$match = {};
query.$match.month = currentMonth.getMonth() + 1;
query.$limit = 5;
query.$sort = {};
query.$sort.created_at = -1;
但是当我执行以下内容时:
DataTable.aggregate(query, function(err, result){
// do something
});
答案 0 :(得分:7)
引用Mongoose's documentation for aggregate
,
<强>参数:强>
[...] <Object, Array>
聚合管道运算符或运算符数组- 醇>
[callback] <Function>
期待你通过
聚合管道运算符数组
DataTable.aggregate([{
$project: {
created_at: '$created_at',
month: {
$month: currentMonth
}
}
}, {
$match: {
month: currentMonth.getMonth() + 1
}
}, {
$limit: 5
}, {
$sort: {
created_at: -1
}
}], function(err, result) {
});
或多个聚合管道运算符作为单独的参数传递
DataTable.aggregate({
$project: {
created_at: '$created_at',
month: {
$month: currentMonth
}
}
}, {
$match: {
month: currentMonth.getMonth() + 1
}
}, {
$limit: 5
}, {
$sort: {
created_at: -1
}
}, function(err, result) {
});
我更喜欢管道构建器方式,
DataTable.aggregate().project({
created_at: '$created_at',
month: {
$month: currentMonth
}
}).match({
month: currentMonth.getMonth() + 1
}).limit(5).sort({
created_at: -1
}).exec(function(err, result) {
});
编辑:如果您更喜欢单独准备单个项目,那么您可以使用数组对象,例如
var query = [];
query.push({
$project: {
created_at: '$created_at',
month: {
$month: currentMonth
}
}
});
query.push({
$match: {
month: currentMonth.getMonth() + 1
}
});
query.push({
$limit: 5
});
query.push({
$sort: {
created_at: -1
}
});
DataTable.aggregate(query, function(err, result) {
});
或使用管道构建器
var aggregator = DataTable.aggregate();
...
aggregator = aggregator.project({...});
...
aggregator = aggregator.match({...});
...
aggregator = aggregator.limit(...);
...
aggregator = aggregator.sort(...);
...
aggregator.exec(function(err, result) {
});