I add some data to firestore which contain #serverstamp, but after I add data , I need to get #serverstamp for other progress
If you're using server side generated timestamps you'll need to query the created document to read the actual timestamp value. Nonetheless, if you need the timestamp maybe it would be more practical to generate the timestamp client side, so the document read isn't needed.
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I am new to NodeJS, MongoDB and express.
I am able to insert, delete and update data but I dont really know how to work with it.
I want to choose some data(e.g. from a dropdown form) and then pass that data to some functions and calculate results. How is it possible to show the results to the client in the webpage(e.g. in a table)?
For example: I have different JSON objects stored in my database and now I want to select one by the name. Then do some calculations with it and show the results to the client.
Also: Is it possible to tell the Database to only accept valid JSON data?
Yes you can get specified data from the database and it will work a lot better with mongoose. You can define schema in mongoose and you can focus more on the data instead of how your data look like. And you can do validation to accept the valid data.
I have the following problem:
We have a table (partitioned by timestamp) that saves data from IoT devices (a lot of data, the expected ratio for new incoming data is about every 30sec each device).
The problem is that we will serving a query service and users can set a "since" and "until" filters over a "ts" field (the timestamp), but I want to paginate the results by 10,20,... (wherever the user sets "pageSize").
How I can do this? since saving the whole result in a temp table (and using Tabledata.list API) is not an option 'cause I would have a temp table for each different request (different in terms of filters...)
Thanks in advance!!!
For Nodejs the library automatically paginates using the token from previous request for you as described here https://cloud.google.com/bigquery/docs/paging-results#bigquery-paging-nodejs
on the other hand you have some options for manual pagination if you read the implementation code here: https://github.com/googleapis/nodejs-bigquery/blob/master/src/index.ts
I am looking to update each document inserted in a couchdb database with the current timestamp.I have referred the document_update_handler feature which can update individual documents.But what i see from the documentation is that an explicit POST/PUT request to the handler function needs to fired along with docid ,something like this:
http://127.0.0.1:5984/my_database/_design/my_designdoc/_update/in-place-query/mydocId.
What i am looking for is a solution that will automatically create new field with the current timestamp just before a new record is inserted.(I am using lightcouch API on the client side to persist a document).
Any help is appreciated.
In past with my PHP / Rails - MYSQL apps I've used the unique ID of a table record to keep track of a record in an html file.
So I'd keep track of how to delete a record shown like this (15 being the ID of the record):
Delete this record
So now I'm using MongoDB. I've tried the same method but the objectID ._id attribute seems to be a loooong byte string that I can't use conveniently.
What's the most sensible way of binding a link in the view to a record (for deletion, or other purposes or whatever)?
If the answer is to create a new id that's unique for each document in the collection, then what's the best way to generate those unique id's?
Thank you.
You could use a counter instead of the ObjectID
But this could create a problem when inserting a new document after you deleted a previous one.
See this blog post for more detail info on Sequential unique identifiers with Node.js and MongoDB.
Or you could use the timestamp part of the ObjectID:
objectId.getTimestamp().toString()
See the node objectid docs
How can I get last created document in couchdb? Maybe some how I can use _changes feature of couchdb? But documentation says, that I only can get list of document, ordered by first created document, ant there is no way to change order.
So how can I get last created document?
You can get the changes feed in descending order as it's also a view.
GET /dbname/_changes?descending=true
You can use limit= as well, so;
GET /dbname/_changes?descending=true&limit=1
will give the latest update.
Your only surefire way to get the last created document is to include a timestamp (created_at or something) with your document. From there, you just need a simple view to output all the docs by their creation date.
I was going to suggest using the last_seq information from the database, but the sequence number changes with every single write, and replication also complicates the matter further.