Select Values transform Icon Select Values

Description

The Select Values transform is useful for selecting, removing, renaming, changing data types and configuring the length and precision of the fields on the stream.

These operations are organized into different categories:

  • Select & Alter — Specify the exact order and name in which the fields have to be placed in the output rows

  • Remove — Specify the fields that have to be removed from the output rows

  • Meta-data - Change the name, type, length and precision (the metadata) of one or more fields

Supported Engines

Hop Engine

Supported

Spark

Maybe Supported

Flink

Maybe Supported

Dataflow

Maybe Supported

Options

General settings

Option Description

Transform Name

Name of the transform: this name has to be unique in a single pipeline

Select & Alter tab

This tab contains options for selecting the fields to forward to the next transform, as well as changing their order. The Get fields to select button will retrieve available fields based on the existing input transforms and populate the entries in this tab.

Option Description

Fieldname

The name of the field from the input stream

Rename to

The new name of the field. Leave blank if you do not wish to rename the field

Length

The field length

Precision

The precision option depends on the field type, but only Number is supported; it returns the number of floating point digits

Include unspecified fields, ordered by name

Enable if you want to implicitly select all other fields from the input stream(s) that are not explicitly selected in the Fields section

Edit Mapping

The Edit Mapping dialog allows you to easily define multiple mappings between source and target fields.

Option Description

Source fields

A list of input fields available to map. Select a field to begin mapping

Target fields

A list of fields that source fields can be mapped to. Once you have selected a source field, select a target field to create a mapping

Add

Adds a source and target field mapping pair to the Mappings section

Delete

Removes a selected Mappings entry

Remove tab

This tab allows you to remove fields from the input stream. Click Get fields to remove to import fields from previous transforms (this will populate the table with all the fields, you’ll probably need to remove those you want to keep in the stream).

Meta-data tab

Options under this tab allow you to rename input fields, convert them to different data types, and alter their length, and precision. Click Get fields to change to import fields from previous transforms.

Option Description

Fieldname

The name of the input field

Rename to

If you want to rename this field, this is where you put the new name

Type

The data type for this field

Length

The field length

Precision

The precision option depends on the field type, but only Number is supported; it returns the number of floating point digits

Binary to Normal?

Converts a string to a numeric data type, when appropriate

Format

The format mask (number type or date format)

Date Format Lenient?

Determines whether the date parser is strict or lenient. Leniency means that invalid date values are processed. If set to N, only strictly valid date values will be accepted; if set to Y, the parser will attempt to determine the intention of an incorrect date, if possible, and correct it.

Date Locale

Specifies the date locale to use for date conversions and calculations. Leave blank to use the default encoding on your system or chose from the populated this list accordingly.

Date Time Zone

Specifies the date time zone to use for date conversions and calculations. Leave blank to use the default encoding on your system or chose from the populated list accordingly.

Lenient number conversion

When this option is set to Y, numbers get parsed until it finds a non-numeric value (e.g. a dash or slash) and stops parsing without reporting an error. When set to N, numbers get parsed strictly throwing an error in case invalid numbers are in the input.

Encoding

Specifies the text file encoding to use. Leave blank to use the default encoding on your system. To use Unicode, specify UTF-8 or UTF-16. On first use, Hop searches your system for available encodings and populates this list accordingly.

Decimal

A decimal point; this is either a dot or a comma

Grouping

A method of separating units of thousands in numbers of four digits or larger. This is either a dot or a comma.

Currency

Symbol used to represent currencies

Special use cases

Duplicating fields

You can send multiple copies of a single field to the next transform, provided that they have different names. Just enter the field to replicate in multiple rows of the Select & Alter tab, and assign each one a different name in the Rename to column.

Use of multiple tabs

Although discouraged for better clarity and simplicity of use, filling more than one tab is possible. They will be processed in the following order:

  1. first the Select & Alter tab is processed: if populated, the fields will be filtered, renamed and reordered as specified

  2. then the Remove tab is processed, but you cannot remove fields that haven’t been selected in the previous step: if you renamed them, you must use the new name in the Fieldname column

  3. finally the Meta-data tab is processed: you cannot change unselected (step 1) and removed (step 2) fields, and if you renamed them you must use the new name in the Fieldname column