One of the biggest issue we face now with parse-server is duplication. Although we have implemented a Parse cloud code to prevent such event through beforeSave
and afterSave
methods at the same time added external middleware to check for existing object before saving still we face duplication over and over specially on concurrent operations.
Here is our code to prevent duplication for a specific class:
Parse.Cloud.beforeSave("Category", function(request, response) {
var newCategory = request.object;
var name = newCategory.get("name");
var query = new Parse.Query("Category");
query.equalTo("name", name);
query.first({
success: function(results) {
if(results) {
if (!request.object.isNew()) { // allow updates
response.success();
} else {
response.error({errorCode:400,errorMsg:"Category already exist"});
}
} else {
response.success();
}
},
error: function(error) {
response.success();
}
});
});
Parse.Cloud.afterSave("Category", function(request) {
var query = new Parse.Query("Category");
query.equalTo("name", request.object.get("name"));
query.ascending("createdAt");
query.find({
success:function(results) {
if (results && results.length > 1) {
for(var i = (results.length - 1); i > 0 ; i--) {
results[i].destroy();
}
}
else {
// No duplicates
}
},
error:function(error) {
}
});
});
This code above is able to prevent some duplicate but most still goes through, example:
What is the "ultimate way" to prevent duplication with Parse server?
You can always create a unique index in mongodb for the field that should be unique in your document.
This way any save that conflicts with that index, will be aborted