Advanced Tab (REST)¶

In this dialog you can configure several advanced settings of the Web service.

Creating a REST Web service: Advanced tab¶

The Virtual DataPort Web services are deployed to an application server (usually in the Web service container embedded in the Denodo Platform). Each time a Web service operation is invoked, it sends a query to the Virtual DataPort server to obtain the required results. It is possible to configure the parameter of these connections established from the Service to the Server: Chunk Size, Chunk Timeout, Query Timeout, Enable Pool, Initial Size and Max. Active. These parameters are explained in the section Connection from the Web Services to the Server.

By default, the Denodo REST Web services explicitly specify that a value of a field is NULL by adding the attribute xsi:nil="true" to the element. E.g. if in a row, the value of the field field_name is NULL, the service returns the following:

<field_name xsi:nil=“true” />

If you do not want the Web Service to specify NULL values with the attribute xsi:nil="true", select the Represent NULL values as empty elements check box. In this way, NULL values will be represented with an empty element. E.g. <field_name />. The problem of enabling this option is that, for text fields, there is no difference between a NULL value and an empty string.

Note that this only applies to the XML representation of the views.

When an application sends a request to a REST web service of Denodo to obtain the data of a view, it can add the parameter “$select” to the URL, to select the fields to project. By default, the value of this parameter can be a comma-separated list of fields and expressions. These are the same expressions you can use in the SELECT clause of a query. E.g. http://denodo-dv-prod-01.acme.com/server/customer360/customer360/views/customer?$select=country%20in%20(‘US’,’UK’,’ES’)

See more about how to use the parameter “$select” in the table Parameters supported by the Denodo RESTful Web service and published REST Web services of the section Input Parameters of the RESTful Web Service.

If you clear the check box Process functions in $select parameter, the value of $select has to be a comma-separated list of fields of the view, not expressions.