I am new to couchDB but have a good experience working with relational databases. Can anyone tell how to connect to couchDB database and retrieve the data stored in it. I am giving an example in relational database and i need help regarding how to do similar task in couchDB.In mysql we use a connector to get connected to the database and the for example we give "select username from tablename where password="abc" ".
CouchDB talks HTTP and JSON, then you can use any HTTP client and JSON parser/generator. You can find a nice introduction in The Definitive Guide.
Try this URL: http://localhost:5984/_utils/, it will open FUTON editor.
CouchDB is a NOSQL database. So it works using HTTP requests (url based). Data that is stored in couchDB is in the form of JSON documents, so there is no concept of tables. In short, database in SQL represent database in couchDB and the rows in a table of SQL represent Documents in couchDB.
Coming back to your question, to retrieve data from couchDB, there is a concept called views which uses Map and Reduce functions (which are JavaScript functions). Using these views couchDB indexes your search function spanning through the complete database (includes all documents), so you need to write a Map function specifying the condition to be used to search. Here's an example -
function(doc) {
if (doc.password) {
emit(doc.username, doc);
}
}
The above example is a simple Map function. Search for the documents of the database where there is a password and return the usernames from all the documents in the database. Password input value (in this case "abc") should be specified in the query string that you will be sending out to couchDB URL. Now, you might ask where is the database specified to search for? I said that we have to create views in order to search. These views are stored in that particular database where you want to search. So, if you want to search a database with name "User_Credentials", then create a view in the "User_Credentials" with the above Map function. More details on how it can be done can be found here: CouchDB Guide to Views
Related
Writing REST API using Nodejs and database is mongodb 3.6.
Collections Names : Subscription, Users and Offering
I am using aggregate function to fetch data from subscription and using lookup I am fetching user which has subscribed.
What I want is in the same output (previous line) I also want to list all the records from offering collection as array.
How do I can get it.
Thanks in advance.
I don't think you can, and neither you should. Getting all records of some collection is bad practice, always try to limit yourself with only things you need.
If you really want to add resutls from some totally unrelated collection then you should make separate request and then add them together in json you sending to client.
I am using mongodb to store items for an auction site
I want to enable fuzzy searching.
Should I query for 1000 results with no parameters then use a js library like fuse.js
Or should I rely on mongodb $regex alone to do the query?
mongodb isn't a great choice for a problem like this. There are lots of great text search utilities available, the most prominent these days being elasticsearch. You'd continue to store your data in mongodb, but you'd keep an elasticsearch instance synced to the mongodb database and perform your searches against elasticsearch. Mongoosastic is a good way to write to both concurrently or Transporter can be used shift the synchronization away from your database persistence flow.
Mongoosastic example:
https://blog.cloudboost.io/sync-mongo-with-elastic-and-save-months-of-development-time-and-cost-d281e0ca8fe4
Some other ways to sync including Transporter: https://code.likeagirl.io/5-different-ways-to-synchronize-data-from-mongodb-to-elasticsearch-d8456b83d44f
I am working with NodeJS and Cloudant (alternatively the DashDB Warehouse if that works better). I wonder if it is possible to have a function in NodeJS that gets called each time a document has been added to the database? I have checked out indexed views but can't really understand how to do it. Does anyone have any good tips regarding this or what documentation to look at?
You can listen to DB _changes in Cloudant (https://console.bluemix.net/docs/services/Cloudant/api/database.html) in continous mode.
Every document change in the Cloudant DB (create,update,delete) will be notified through this channel.
There are different nodejs libraries you can use with this purpose. This is
one example: https://www.npmjs.com/package/cloudant-follow
I am learning PouchDB with CouchDB and trying to wrap my head around intercepting documents to the couchdb server and performing an action on it wether it be creating other documents, updating the user table, etc.
On the server the json document will be treated through a business layer before it is submitted to the couchdb server, preferably in .net.
Is this possible? If not, is there a way to do so?
Thanks!
On the server side, you can listen to the _changes feed from CouchDB (docs here) and react whenever a document is added, modified, or deleted. This could be useful for reporting/messaging/aggregation/etc.
Alternatively, if you want to do some schema validation on the documents before they are accepted, then you should look into adding a design doc with a validate_doc_update field (docs here).
I am using pouchdb on client side and couchdb on server side. and both are in sync.
I am accessing couchdb from java using client-api lightpouch.
I am storing transaction data, each transaction is stored as document by prefixed _id like
Transaction_1,
Transaction_2
..
..
so on
Now i want to access all the documents where the _id field starts with Transaction on the server.
This is possible in pouchdb and i am able to achieve that.
But i am wondering how can i achieve the same at server side, in java using lightcouch.
Or is there any Java client-API available that provides this kind of functionality. ??
To find all documents whose _ids match a certain prefix, you only need to do:
/_all_docs?startkey="foo"&endkey="foo\uffff"
(For the prefix "foo".)
I wrote up a bit about why this works here.
LightCouch aims at providing a simple API
for communicating with CouchDB databases.
What you need is a CouchDB view server-side which you can request with LightCouch.