Extractlist Transform

While the new column contains array data, the data type of the new column is sometimes inferred as String. 

Basic Usage

Your source column (myWidgetInventory) is formatted in the following manner:

{ "red":"100","white":"1300","blue":"315","purple":"55"}

The following step extracts the raw inventory contents of each color:

extractlist col: myWidgetInventory on:`{digit}+`

Output: The generated column contains data that looks like the following array:

["100","1300","315","55"]

Syntax and Parameters

extractlist: col:column_ref on:string_literal_pattern delimiter:string_literal_pattern [quote:'quoted_string'] [as:'new_column_name']

For more information on syntax standards, see Language Documentation Syntax Notes.

col

Identifies the column to which to apply the transform. You can specify only one column.

Usage Notes:

on

For the extractlist tranform, all instances that match this pattern in the source column are extracted into the array list in the new column. Each occurrence in the generated array corresponds to an individual instance in the source; the new column can contain duplicate values.

To create array elements based only on the delimiter parameter, set the following regular expression:

on:`/+/`

Usage Notes:

delimiter

{ key1=value1,key2=value2 }

For this transform, this parameter defines the pattern that separates the values that you want to extract into the array.

Usage Notes:

quote

extractlist col: MySourceValues on:`{alpha}+` delimiter:';' quote:'\"'

Output: Extracts from the MySourceValues column each instance of a string value that occurs before the delimiter. Values between double-quotes are considered string literals and are not processed according to the delimiters defined in the transform. 

Can be used to specify a string as a single quoted object. This parameter value can be one or more characters.

Usage Notes:

• The quote value can appear anywhere in the column value. It is not limited by the constraints of any other parameters.

as

Usage Notes:

Examples

Example - extract query parameters from URLs

Source:

In this example, a list of URLs identifies the items in the shopping carts of visitors to your web site. You want to extract the shopping cart information embedded in the query parameters of the URL.

Transformation:

The following transformation extracts the list of query values from the URL. Note that the equals sign is included in the matching pattern so that you don't accidentally pick up numeric values from the non-parameter part of the URL:

The two query parameter values have been extracted into an array of values, including the equals sign, which must be removed:

You can now unnest these values into separate columns:

After you rename the two columns to prodId and Qty, you can delete the column generated by the first transformation.

Results:

Example - Extracting counts from a ragged array using extractlist