How to avoid duplicate entries in the MetoDroid app
How to avoid duplicate records in mongoDb in Meteor app.
In a team: db.products.find({},{"TEMPLATE_NAME": 1},{unique : true})
{ "_id" : ObjectId("5555d0a16ce3b01bb759a771"), "TEMPLATE_NAME" : "B" }
{ "_id" : ObjectId("5555d0b46ce3b01bb759a772"), "TEMPLATE_NAME" : "A" }
{ "_id" : ObjectId("5555d0c86ce3b01bb759a773"), "TEMPLATE_NAME" : "C" }
{ "_id" : ObjectId("5555d0f86ce3b01bb759a774"), "TEMPLATE_NAME" : "C" }
{ "_id" : ObjectId("5555d1026ce3b01bb759a775"), "TEMPLATE_NAME" : "A" }
{ "_id" : ObjectId("5555d1086ce3b01bb759a776"), "TEMPLATE_NAME" : "B" }
I only want to get unique template names and show them in HTML page.
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Use an aggregation framework where your pipeline stages consist of and operators respectively. The operational command groups the input documents by the given key and thus returns the result as a result. The operator converts each document to a stream, for example by adding new fields or removing existing fields: $group
$project
$group
$project
db.products.aggregate([
{
"$group": {
"_id": "$TEMPLATE_NAME"
}
},
{
"$project": {
"_id": 0,
"TEMPLATE_NAME": "$_id"
}
}
])
Result:
/* 0 */
{
"result" : [
{
"TEMPLATE_NAME" : "C"
},
{
"TEMPLATE_NAME" : "A"
},
{
"TEMPLATE_NAME" : "B"
}
],
"ok" : 1
}
Then you can use meteorhacks: aggregate package to implement aggregation in Meteor:
Add to your application
meteor add meteorhacks:aggregate
Then just use as shown below. .aggregate
var products = new Mongo.Collection('products');
var pipeline = [
{
"$group": {
"_id": "$TEMPLATE_NAME"
}
},
{
"$project": {
"_id": 0,
"TEMPLATE_NAME": "$_id"
}
}
];
var result = products.aggregate(pipeline);
- UPDATE -
An alternative that doesn't use aggregation is to use the underscore methods to return different field values from the collection search method as follows:
var distinctTemplateNames = _.uniq(Collection.find({}, {
sort: {"TEMPLATE_NAME": 1}, fields: {"TEMPLATE_NAME": true}
}).fetch().map(function(x) {
return x.TEMPLATE_NAME;
}), true)
;
This will return an array with different product template names ["A", "B", "C"]
You can check out some tutorials that explain the above approach in detail: Get unique values from collection in Meteor and METEOR - MONDOD DISCLAIMER .
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