CouchDB Reader Parameters

About Database Connections

Database formats include a Database Connection parameter that defines and stores authentication information. For general information about sharing database connections, please see Using Database Connections.

Note that Database Connection parameters differ slightly, depending on context and/or database format.

Connection

From the Connection parameter in a database format, you can do one of the following:

  • Select an existing, previously defined connection. See the section Reusing a Database Connection in Using Database Connections
  • Select Add Database Connection to define a new connection. See database-specific parameters below, as well as the section Adding a Database Connection in a Workspace in Using Database Connections The new connection can be made visible only to the current user, or can be shared among multiple users.

The Service URL of the CouchDB dataset to access. This can be:

http://<host>:<port>/<root>[/<databasename>]

This parameter is required. The leading http:// is optional. Only the host name is required, usually followed by a port number. For example:

http://127.0.0.1:5984

mycouchddserver:5984

The values for these parameters specify the user name and password combination with which to log into the CouchDB server.

If left unspecified, only public database tables will be available to read.

Constraints

Tables

After specifying the database connection, click the Browse button (...) to select tables for import. A connection window appears while the system retrieves the tables from the database.

Once the Select Tables dialog appears, you can select one or more tables. Click OK to dismiss the window and add the selected table name(s) to the Tables parameter.

JSON Attribute Handling

The parameter controls how the reader creates attributes from JSON document fields:

  • One Level – Expand Arrays (default): The reader treats object fields as string attributes. Array fields at the top level of the JSON document are treated as list attributes.
  • All Levels: The reader flattens all fields in the document as separate attributes. Fields within an object are treated as attributes with a ‘.’ in the attribute name. Fields within an array are treated as list attributes.
  • One Level: The reader treats both object and array fields as string attributes.

Example:

	{
		“a”: 1,
		“object”: {
			“b”: 2,
			“c”: 3
		},
		“array”: [
			{
				“d”: 4
			},
			5
		]		
	}

If flattening mode is One Level – Expand Arrays:

  • a : 1
  • object : { “b”: 2, “c”: 3 }
  • array{0} : { “d”: 4 }
  • array{1} : 5

If flattening mode is All Levels, then the feature attributes would be:

  • a : 1
  • object.b : 2
  • object.c : 3
  • array{0}.d : 4
  • array{1} : 5

If flattening mode is One Level:

  • a : 1
  • object : { “b”: 2, “c”: 3 }
  • array : [ { “d”: 4 }, 5 ]

Specifies whether or not output features will have the couchdb_raw_json format attribute populated with the serialized representation of the JSON document.

If set to Yes, the couchdb_raw_json format attribute will automatically be exposed, and there will be no user attributes on the schema.

Advanced

Specifies how many features are read from the server at a time.

Setting a high value can result in increased performance, as there can be significant overhead associated with each network request.

Use this parameter to expose Format Attributes in Workbench when you create a workspace:

  • In a dynamic scenario, it means these attributes can be passed to the output dataset at runtime.
  • In a non-dynamic scenario, this parameter allows you to expose additional attributes on multiple feature types. Click the browse button to view the available format attributes (which are different for each format) for the reader.

Using the minimum and maximum x and y parameters, define a bounding box that will be used to filter the input features.

Only features that intersect with the bounding box are returned. (Note that this is the bounding box intersection only, and not a full geometry intersection that would be returned by a transformer like the SpatialFilter.)

If all four coordinates of the search envelope are specified as 0, the search envelope will be disabled.

Search Envelope Coordinate System

Specifies the coordinate system of the search envelope if it is different than the coordinate system of the data. The coordinate system associated with the data to be read must always be set if this parameter is set.

If this parameter is set, the minimum and maximum points of the search envelope are reprojected from the Search Envelope Coordinate System to the reader’s coordinate system prior to applying the envelope.

Clip to Search Envelope

When selected, this parameter removes any portions of imported features being read that are outside the Search Envelope.

The example below illustrates the results of the Search Envelope when Clip to Search Envelope is not selected (set to No) and when it is selected (set to Yes).

  • No: Any features that cross the search envelope boundary will be read, including the portion that lies outside of the boundary.
  • Yes: Any features that cross the search envelope boundary will be clipped at the boundary, and only the portion that lies inside the boundary will be read. The underlying function for the Clip to Search Envelope function is an intersection; however, when Clip to Search Envelope is selected, a clipping operation is also performed in addition to the intersection.