Extractkv Transform
注意
Transforms are a part of the underlying language, which is not directly accessible to users. This content is maintained for reference purposes only. For more information on the user-accessible equivalent to transforms, see Transformation Reference.
Extracts key-value pairs from a source column and writes them to a new column.
Source column must be of String type, although the data can be formatted as other data types. The generated column is of Object type.
Your source column (MyKeyValues) is formatted in the following manner:
key1=value1,key2=value2
Basic Usage
The following transform extracts the key-value pairs. The key parameter contains a single pattern that matches all keys that you want to extract:
extractkv col: MyKeyValues key:`{alpha}+{digit}` valueafter: '=' delimiter: ','
Output: The generated column contains data that looks like the following:
{"key1":"value1","key2":"value2"}If the source data contained additional keys which were not specified in the transform, those key-value pairs would not appear in the generated column.
Syntax and Parameters
extractkv col:column_ref delimiter:string_literal_pattern key:string_literal_pattern valueafter:string_literal_pattern [as:'new_column_name']
Parameter | Required? | Data Type | Description |
|---|---|---|---|
extractkv | Y | transform | Name of the transform |
col | Y | string | Source column name |
delimiter | Y | string | String literal or pattern that identifies the separator between key-value pairs |
key | Y | string | Pattern that identifies the key to match |
valueafter | Y | string | String literal or pattern after which is located a key's value |
as | N | string | Name of the newly generated column |
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:
Required? | Data Type |
|---|---|
Yes | String (column name) |
delimiter
Specifies the character or pattern that defines the end of a key-value pair. This value can be specified as a String literal, regular expression, or Wrangle.
In the following:
{ key1=value1,key2=value2 } The delimiter is the comma ( ','). The final key-value pair does not need a delimiter.
提示
You can insert the Unicode equivalent character for this parameter value using a regular expression of the form /\uHHHH/. For example, /\u0013/ represents Unicode character 0013 (carriage return). For more information, see Supported Special Regular Expression Characters.
Usage Notes:
Required? | Data Type |
|---|---|
Yes | String (literal, regular expression, orWrangle) |
key
Specifies the pattern used to extract the keys from a source column by the extractkv transform. For the following data:
{ key1=value1,key2=value2 }The keys are represented in the transform by the following parameter and value:
key:`{alpha}+{digit}`This pattern matches all keys that begin with a letter and end with a digit. If the source data contains other keys, they do not appear in the extracted data.
Usage Notes:
Required? | Data Type |
|---|---|
Yes | Single pattern representing the individual keys to extract. |
valueafter
Specifies the character or pattern after which the value is specified in a key-value pair. This value can be specified as a String literal, regular expression, or Wrangle .
For the following:
{ key1=value1,key2=value2 } The valueafter string is the equals sign ( '=').
Usage Notes:
Required? | Data Type |
|---|---|
Yes | String (literal, regular expression, orWrangle) |
as
Name of the new column that is being generated. If the as parameter is not specified, a default name is used.
Usage Notes:
Required? | Data Type |
|---|---|
No | String (column name) |
Examples
提示
For additional examples, see Common Tasks.
Example - extracting key values from car data and the unnesting into separate columns
This example shows how you can unpack data nested in an Object into separate columns.
Source:
You have the following information on used cars. The VIN column contains vehicle identifiers, and the Properties column contains key-value pairs describing characteristics of each vehicle. You want to unpack this data into separate columns.
VIN | Properties |
|---|---|
XX3 JT4522 | year=2004,make=Subaru,model=Impreza,color=green,mileage=125422,cost=3199 |
HT4 UJ9122 | year=2006,make=VW,model=Passat,color=silver,mileage=102941,cost=4599 |
KC2 WZ9231 | year=2009,make=GMC,model=Yukon,color=black,mileage=68213,cost=12899 |
LL8 UH4921 | year=2011,make=BMW,model=328i,color=brown,mileage=57212,cost=16999 |
Transformation:
Add the following transformation, which identifies all of the key values in the column as beginning with alphabetical characters.
The
valueafterstring identifies where the corresponding value begins after the key.The
delimiterstring indicates the end of each key-value pair.
Transformation Name | |
|---|---|
Parameter: Column | Properties |
Parameter: Key | `{alpha}+` |
Parameter: Separator between key and value | `=` |
Parameter: Delimiter between pair | ',' |
Now that the Object of values has been created, you can use the unnest transform to unpack this mapped data. In the following, each key is specified, which results in separate columns headed by the named key:
注意
Each key must be entered on a separate line in the Path to elements area.
Transformation Name | |
|---|---|
Parameter: Column | extractkv_Properties |
Parameter: Paths to elements | year |
Parameter: Paths to elements | make |
Parameter: Paths to elements | model |
Parameter: Paths to elements | color |
Parameter: Paths to elements | mileage |
Parameter: Paths to elements | cost |
Results:
When you delete the unnecessary Properties columns, the dataset now looks like the following:
VIN | year | make | model | color | mileage | cost |
|---|---|---|---|---|---|---|
XX3 JT4522 | 2004 | Subaru | Impreza | green | 125422 | 3199 |
HT4 UJ9122 | 2006 | VW | Passat | silver | 102941 | 4599 |
KC2 WZ9231 | 2009 | GMC | Yukon | black | 68213 | 12899 |
LL8 UH4921 | 2011 | BMW | 328i | brown | 57212 | 16999 |