couchDB Vignette
In couchDB: Connect to and Work with CouchDB Databases

Updated on June 10, 2016 by FvD

Abstract

The couchDB package has been designed for communication with couchDB, a popular noSQL database. For details consult the help pages for

couch_http_connection
couch_create_database
couch_fetch
couch_store

1 Get connected

To interact with a couchDB instance you will need to create a connection object. Communication with couchDB happens over a http protocol. A minimal connection (running on the default port and no password protection) would be:

library(couchDB)
myConn  <- couch_http_connection("localhost")

The variable "myConn" can now be used as parameters to other functions.

For convenience a default connection can also be created with couch_set_default_connection using the same parameters.

Once a connection object exists, you may want to make sure it is connecting correctly with the couch_ping function. If you are properly connected the reponse should look like:

  Response [http://localhost:5984]
  Status: 200
  Content-type: text/plain; charset=utf-8
  Size: 151 B
  {"couchdb":"Welcome","uuid":"c1a367c91517195b57ddafe788a72b75","version":"1.4.0","vendor"
  {"name":"...

To connect to cloudant specify the service (otherwise it defaults to couchdb) as follows:

myConn <- couch_http_connection(host = "demo.cloudant.com",
                                    https = TRUE,
                                    service = "cloudant")

Response [https://demo.cloudant.com/]
  Date: 2016-05-13 16:50
  Status: 200
  Content-Type: application/json
  Size: 64 B
{"couchdb":"Welcome","version":"1.0.2","cloudant_build":"2580"}

2. Working with couchDB databases

On a couchDB install there can be several databases (i.e. namespaces). The function

couch_list_databases

will provide a list of available databases on the connection provided.

The function couch_create_database will, similarly, allow you to create a new database or namespace on the couchDB instance.

3. Setting defaults

CouchDB allows for setting a default connection and a default database to work with. This is useful, and provides for cleaner code, if you are mainly working with one specific database at a specific connection.

4. Working with documents

Once you have a connection and a database to work with you can fetch, store and delete documents by using the corresponding functions:

couch_fetch
couch_fetch_default
couch_store
couch_store_default
couch_delete

The document to be stored can be provided either as a list (which will be converted to json for insertion), or for tighter control over the document structure a character vector in json format can be provided.