jsonpatharraydefaultempty.md

description
This section contains reference documentation for the JSONPATHARRAYDEFAULTEMPTY function.

JSONPATHARRAYDEFAULTEMPTY

Extracts an array from jsonField based on 'jsonPath', the result type is inferred based on JSON value. Returns empty array for null or parsing error. This function can only be used in an ingestion transformation function.

Signature

JSONPATHARRAYDEFAULTEMPTY(jsonField, 'jsonPath')

Arguments	Description
jsonField	An Identifier/Expression contains JSON documents.
'jsonPath'	Follows JsonPath Syntax to read values from JSON documents.

{% hint style="warning" %} 'jsonPath'` is a literal. Pinot uses single quotes to distinguish them from identifiers.

You can use the Jayway JsonPath Evaluator Tool to test JSON expressions before you import any data. {% endhint %}

Usage Examples

The usage examples are based on extracting fields from the following JSON document:

{
  "data": {
    "name": "Pete",
    "age": 24,
    "subjects": [
      {
        "name": "maths",
        "homework_grades": [80, 85, 90, 95, 100],
        "grade": "A",
        "score": 90
      },
      {
        "name": "english",
        "homework_grades": [60, 65, 70, 85, 90],
        "grade": "B",
        "score": 70
      }
    ]
  }
}

Expression	Value
JSONPATHARRAYDEFAULTEMPTY(myJsonRecord, '$.subjects[*].name')	["maths", "english"]
JSONPATHARRAYDEFAULTEMPTY(myJsonRecord, '$.subjects[*].score')	[90, 70]
JSONPATHARRAYDEFAULTEMPTY(myJsonRecord, '$.subjects[*].homework_grades[1]')	[85, 65]
JSONPATHARRAYDEFAULTEMPTY(myJsonRecord, '$.subjects[*].homework_grades[7]')	[]

This function can be used in the table config to extract the name, score, and second value of homework_grades into their respective columns , as described below:

{
   "tableConfig":{
      "ingestionConfig":{
         "transformConfigs":[
            {
               "columnName":"names",
               "transformFunction":"JSONPATHARRAYDEFAULTEMPTY(data, '$.subjects[*].name')"
            },
            {
               "columnName":"ages",
               "transformFunction":"JSONPATHARRAYDEFAULTEMPTY(data, '$.subjects[*].score')"
            },
            {
               "columnName":"homeworkGrades",
               "transformFunction":"JSONPATHARRAYDEFAULTEMPTY(data, '$.subjects[*].homework_grades[1]')"
            }
         ]
      }
   }
}