Input port reading

Development > Component reference > Readers > Common properties of Readers > Input port reading

Input port reading allows you to read file names or data from an optional input port. This feature is available in most of Readers.

To use input port mapping, connect an edge to an input port. Assign metadata to the edge. In the Reader, edit the File URL attribute.

The attribute value has the syntax port:$0.FieldName[:processingType]. You can enter the value directly or with help of URL file dialog.

Here processingType is optional and defines if the data is processed as plain data or URL addresses. It can be source, discrete, or stream. If not set explicitly, discrete is applied by default.

Processing type

discrete

Each data record field from an input port represents one particular data source.
source

Each data record field from an input port represents a URL to be loaded in and parsed.
stream

All data fields from an input port are concatenated and processed as one input file. If the null value of this field is met, it is replaced by the EOF. Following data record fields are parsed as another input file in the same way, i.e. until the null value is met. The Reader starts parsing data as soon as first bytes come by the port and process it progressively until EOF comes. For more information about writing with stream processing type, see Output port writing.

Input port metadata

In input port reading, only metadata field of some particular data types can be used. The type of the FieldName input field can only be string, byte or cbyte.

Processing of input port record

When graph runs, data is read from original data source (according to metadata of an edge connected to an optional input port of Readers) and received by a Reader through its optional input port. Each record is read independently of the other records. The specified field of each one is processed by the Reader according to the output metadata.

Readers with input port reading

Remember that port reading can also be used by DBExecute for receiving SQL commands. Query URL will be as follows: port:$0.fieldName:discrete. Also an SQL command can be read from a file. Its name, including path, is then passed to DBExecute from an input port and the Query URL attribute should be the following: port:$0.fieldName:source.