I am working on my first project using Meteor, and am having some difficulty with sorting.
I have a form where users enter aphorisms that are then displayed in a list. Currently the most recent aphorisms automatically display at the bottom of the list. Is there an easy way to have the most recent appear at the top of the list instead?
I tried:
Template.list.aphorisms = function () {
return Aphorisms.find({}, {sort: {$natural:1}});
};
And am stumped because the Meteor docs don't have many examples.
Assuming that the date_created is in a valid date format along with the timestamp, You should insert the parsed value of date_created using Date.parse() javascript function, which gives the number of milliseconds between January 1, 1970 and date value contained in date_created.
As a result of that, the most recently added record will contain greater value of date_created than the record inserted before it.
Now when fetching the records, sort the cursor in descending order of the date_created parameter as:
Aphorisms.find({}, {sort: {date_created: -1}});
This will sort records from newer to older.
I've found the following to be a cleaner solution:
Template.list.aphorisms = function () {
return Aphorisms.find().fetch().reverse();
};
Given that entire collection already exists in the reverse order that you would like, you can simply create an array of all the objects and reverse the order.
Related
I have been trying to figure out a way to query a list of documents where I have a range filter on one field and order by another field which of course isn't possible, see my other question: Order by timestamp with range filter on different field Swift Firestore
But is it possible to save documents with the timestamp as id and then it would sort by default? Or maybe hardcode an ID, then retrieve the last created document id and increase id by one for the next post to be uploaded?
This shows how the documents is ordered in the collection
Any ideas how to store documents so they are ordered by created at in the collection?
It will order by document ID (ascending) by default in Swift.
You can use .order(by: '__id__') but the better/documented way is with FieldPath documentID() I don't really know Swift but I assume that it's something like...
.order(by: FirebaseFirestore.FieldPath.documentID())
JavaScript too has an internal variable which simply returns __id__.
.orderBy(firebase.firestore.FieldPath.documentId())
Interestingly enough __name__ also works, but that sorts the whole path, including the collection name (and also the id of course).
If I correctly understood your need, by doing the following you should get the correct order:
For each document, add a specific field of type number, called for example sortNbr and assign as value a timestamp you calculate (e.g. the epoch time, see Get Unix Epoch Time in Swift)
Then build a query sorted on this field value, like:
let docRef = db.collection("xxxx")
docRef.order(by: "sortNbr")
See the doc here: https://firebase.google.com/docs/firestore/query-data/order-limit-data
Yes, you can do this.
By default, a query retrieves all documents that satisfy the query in
ascending order by document ID.
See the docs here: https://firebase.google.com/docs/firestore/query-data/order-limit-data
So if you find a way to use a timestamp or other primary key value where the ascending lexicographical ordering is what you want, you can filter by any fields and still have the results sorted by the primary key, ascending.
Be careful to zero-pad your numbers to the maximum precision if using a numeric key like seconds since epoch or an integer sequence. 10 is lexicographical less than 2, but 10 is greater than 02.
Using ISO formatted YYYY-mm-ddTHH:MM:SS date-time strings would work, because they sort naturally in ascending order.
The order of the documents shown in the Firebase console is mostly irrelevant to the functioning of your code that uses Firestore. The console is just for browsing data, and that sorting scheme makes it relatively intuitive to find a document you might be looking for, if you know its ID. You can't change this sort order in the console.
Your code is obviously going to have other requirements, and those requirements should be coded into your queries, without regarding any sort order you see in the dashboard. If you want time-based ordering of your documents, you'll have to store some sort of timestamp field in the document, and use that for ordering. I don't recommend using the timestamp as the ID of a document, as that could cause problems for you in the future.
I have a data set where I want to dynamically sort by date (both ascending and descending) on the fly. I read through the docs and as instructed I've created a slave index of my master index, where the top ranking value is my 'date' ordered by DESC. The date is in the correct integer and unix timestamp format.
My question is how do I query this new index on the fly using the front end Javascript Algolia API?
Right now, my code looks like the following:
this.client = algoliasearch("xxxx", "xxxxx");
this.index = this.client.initIndex('master_index');
this.index.search(
this.query, {
hitsPerPage: 10,
page: this.pagination,
facets: '*',
facetFilters: facetArray
},
function(error, results) {
// do stuff
}.bind(this));
What I've tried doing is to just change the initIndex to use my slave index instead and this does work...but I'm thinking that this is slow and inefficient if I need to reinitialize the index every time the user just wants to sort by date. Isn't there a parameter instead that I can insert in the query to sort by date?
Also, my second question is that even when I change the index to the slave index, it only sorts by descending. How can I have it sort by ascending as well?
I really do not want to create ANOTHER slave index just to sort by ascending date since I have many thousands of rows and am already close to exceeding my record limit. Surely there must be another way here?
Thanks!
What I've tried doing is to just change the initIndex to use my slave index instead and this does work...but I'm thinking that this is slow and inefficient if I need to reinitialize the index every time the user just wants to sort by date. Isn't there a parameter instead that I can insert in the query to sort by date?
You should store all the indices you want to do sorts in different properties on the this object:
this.indices = {
mostRelevant: this.client.initIndex('master_index'),
desc: this.client.initIndex('slave_desc')
};
Then you can use this.indices.mostRelevant.search() or this.indices.desc.search().
This is not a performance issue to do so.
Also see the dedicated library to create instant-search experiences: https://community.algolia.com/instantsearch.js/
Also, my second question is that even when I change the index to the slave index, it only sorts by descending. How can I have it sort by ascending as well?
I really do not want to create ANOTHER slave index just to sort by ascending date since I have many thousands of rows and am already close to exceeding my record limit. Surely there must be another way here?
This is the only true way to do sorts in Algolia. This is by design what makes Algolia so fast and is currently the only way to do so.
I am wondering if there is a way to order a result set based on the date component in an object Id
myCol.find().sort('_id descending').limit(5).select('title _id').exec(function(e, data){
res.render('some-page.html',{data:data});
});
I don't have an explicit date field in my documents, but it's my understanding that objectId already contains a date component, so I am wondering if I can take advantage of that here.
The above code will not correctly order the result set
EDIT:
By updating the query slightly I got it to work
myCol.find().sort([['_id', -1]])
Source: uses for mongodb ObjectId creation time
The simplest way to sort descending with Mongoose is to prefix the field name in your call so sort with a -:
myCol.find()
.sort('-_id')
.limit(5)
.select('title _id')
.exec(function(e, data){
res.render('some-page.html',{data:data});
});
I have a collection of data and I want to get it sorted by insertion time. I have not any additional fields to store the insert time. But as I found out I can get this time from Id.
I have tried this code:
return bookmarks.find({}, {sort: {_id.getTimestamp(): 1}, limit: 10});
or
return bookmarks.find({}, {sort: {ObjectId(_id).getTimestamp(): 1}, limit: 10});
but get the error message:
=> Your application has errors. Waiting for file change.
Is there any way to sort collection by insertion datetime using only id field ?
At the moment this isn't possible with Meteor, even if it is with MongoDB. The ObjectID's created with meteor don't bear a timestamp. See http://docs.meteor.com/#collection_object_id
The reason for this is client side code can insert code and it can arrive late on the server, hence there is no guarantee the timestamp portion of the ObjectID will be accurate. In addition to the latency the client side's date is used meaning if they're off it's going to get you incorrect data. I think this is the reason they use an ObjectID but it is completely random.
If you want to sort by date you have to store the time/date separately.
The part what i striked out is not accurate. Meteor use it is own id generation which is based on a random string that is while does not apply the doc what i linked before. Check sasha.sochka's comment under.
It is nearly but not 100% good if you just sort for the _id field . While as it is constructed the first 4 byte is the timestamp in secs (so sorting for the getTimestamps value is not better). Under one second resolution you cannot get the exact order, as it is mentioned in the documentation: http://docs.mongodb.org/manual/reference/object-id/#objectid
It is still true that you can try to check the exact order of the insert/update ops against your collection in the oplog, if you have an oplog, but as it is a capped collection anyway you will see the recent operations only. http://docs.mongodb.org/manual/core/replica-set-oplog/.
I am very new to mongodb
I have a database with sale_date and the value is saved as text and the format is "dd:mm:yyyy". Now I want to query based on the date. Like I want to query the last month's entry.
I also have field sale_time and also saved as text and the format is "hh:mm" and I want to query the last hour's entry.
**I want to query from java and also from the mongo console.
One row of my collection:
{
"_id":112350,
"sale_date":"21.07.2011",
"sale_time":"18:50",
"store_id":"OK3889-45",
"region_code":45,
"product_id":"QKDGLHX5061",
"product_catagorie":53,
"no_of_product":1,
"price":1211.37,
"total_price":1211.37
}
I have million of entries. Now I want to find the entries for the month of July 2011 or hour from 18:00 to 19:00 in 21.07.2013.
You can query with a regex matching your results. You said format dd:mm:yyyy but the example looks like dd.mm.yyyy so I used that in examples
For example:
db.sales.find({sale_date: /..\.07\.2011/})
This will be ineficient since it can't use an index, but it will get the job done.
It would be better, if you stick with dates as strings to reverse the order to yyyy:mm:dd then you could use a anchored regex, which will hit an index like:
db.sales.find({sale_date: /2011\.07/})
For the hour query:
db.sales.find({sale_date: "21.07.2013", sale_time: {$gte: "18:00", $lt: "19:00"}})
There is no efficient and reliable way to query the for a date range you want given the date structure you have used. A regex style query would scan through the entire collection for example, and if you have millions of documents, that's not acceptable.
You could theoretically create a MapReduce to better structure the data into a new collection. But, that will be more work to maintain (as MapReduces aren't automatically updated, and may make other queries and data fetching involve more steps than you'd like).
Although, if you're willing to do that, I'd strongly suggest you instead just fix your data as I mentioned in my comment to be a standard YYYYMMDD. Even better, you may want to consider merging the time and would be to include the time stamp in the same field:
2013-07-21T14:30
If you don't though, you can still do the single date query reasonably (although you'd want to index both the date and time as a compound index):
db.sales.ensureIndex({ sale_date: 1, sale_time: 1})
Regarding the code, it's basically going to look like this:
BasicDBObject date = new BasicDBObject("sale_date", "21.07.2013");
BasicDBObject time = new BasicDBObject("sale_time",
new BasicDBObject("$gte", "18:00").
append("$lte", "19:00"));
BasicDBObject andQuery = new BasicDBObject();
List<BasicDBObject> obj = new ArrayList<BasicDBObject>();
obj.add(date);
obj.add(time);
andQuery.put("$and", obj);
cursor = coll.find(andQuery);