Column Level Lineage Dataset Facet

Column level lineage provides fine grained information on datasets' dependencies. Not only we know the dependency exist, but we are also able to understand which input columns are used to produce which output columns and in what way. This allows answering questions like Which root input columns are used to construct column x?

For example, a Job might executes the following query:

INSERT INTO top_delivery_times (
    order_id,
    order_placed_on,
    order_delivered_on,
    order_delivery_time
)
SELECT
    order_id,
    order_placed_on,
    order_delivered_on,
    DATEDIFF(minute, order_placed_on, order_delivered_on) AS order_delivery_time,
FROM delivery_7_days
ORDER BY order_delivery_time DESC
LIMIT 1;

This would establish the following relationships between the delivery_7_days and top_delivery_times tables:

An OpenLinage run state update that represent this query using column-level lineage facets might look like:

{
    "eventType": "START",
    "eventTime": "2020-02-22T22:42:42.000Z",
    "run": ...,
    "job": ...,
    "inputs": [
        {
          "namespace": "food_delivery",
          "name": "public.delivery_7_days"
        }
    ],
    "outputs": [
        {
            "namespace": "food_delivery",
            "name": "public.top_delivery_times",
            "facets": {
                "columnLineage": {
                    "_producer": "https://github.com/MarquezProject/marquez/blob/main/docker/metadata.json",
                    "_schemaURL": "https://openlineage.io/spec/facets/1-0-1/ColumnLineageDatasetFacet.json",
                    "fields": {
                        "order_id": {
                            "inputFields": [
                                {
                                    "namespace": "food_delivery",
                                    "name": "public.delivery_7_days",
                                    "field": "order_id",
                                    "transformations": [
                                        {
                                            "type": "DIRECT",
                                            "subtype": "IDENTITY",
                                            "description": "",
                                            "masking": false
                                        }
                                    ]
                                }
                            ]
                        },
                        "order_placed_on": {
                            "inputFields": [
                                {
                                    "namespace": "food_delivery",
                                    "name": "public.delivery_7_days",
                                    "field": "order_placed_on",
                                    "transformations": [
                                        {
                                            "type": "DIRECT",
                                            "subtype": "IDENTITY",
                                            "description": "",
                                            "masking": false
                                        }
                                    ]                                  
                                }
                            ]
                        },
                        "order_delivered_on": {
                            "inputFields": [
                                {
                                    "namespace": "food_delivery",
                                    "name": "public.delivery_7_days",
                                    "field": "order_delivered_on",
                                    "transformations": [
                                        {
                                            "type": "DIRECT",
                                            "subtype": "IDENTITY",
                                            "description": "",
                                            "masking": false
                                        }
                                    ]
                                }
                            ]
                        },
                        "order_delivery_time": {
                            "inputFields": [
                                {
                                    "namespace": "food_delivery",
                                    "name": "public.delivery_7_days",
                                    "field": "order_placed_on",
                                    "transformations": [
                                        {
                                            "type": "DIRECT",
                                            "subtype": "TRANSFORMATION",
                                            "description": "",
                                            "masking": false
                                        }
                                    ]
                                },
                                {
                                    "namespace": "food_delivery",
                                    "name": "public.delivery_7_days",
                                    "field": "order_delivered_on",
                                    "transformations": [
                                        {
                                            "type": "DIRECT",
                                            "subtype": "TRANSFORMATION",
                                            "description": "",
                                            "masking": false
                                        }
                                    ]
                                }
                            ]
                        }
                    }
                }
            }
        }
    ],
    ...
}

The facet specification can be found here.

Transformation Type

To provide the best information about each field lineage, each inputField of an output can contain the transformations field. This field describes what is the nature of relation between the input and the output columns. Each transformation is described by 4 fields: type, subtype, description and masking.

Type

Indicates how direct is the relationship e.g. in query

SELECT 
    source AS result 
FROM TAB 
WHERE pred = true;

1. DIRECT - output column value was somehow derived from inputField value. In example result value is derived from source
2. INDIRECT - output column value is impacted by the value of inputField column, but it's not derived from it. In example no part result value is derived from pred but pred has impact on the values of result in the output dataset

Subtype

Contains more specific information about the transformation Direct

• Identity - output value is taken as is from the input
• Transformation - output value is transformed source value from input row
• Aggregation - output value is aggregation of source values from multiple input rows Indirect
• Join - input used in join condition
• GroupBy - output is aggregated based on input (e.g. GROUP BY clause)
• Filter - input used as a filtering condition (e.g. WHERE clause)
• Order - output is sorted based on input field
• Window - output is windowed based on input field
• Conditional - input value is used in IF of CASE WHEN statements

Masking

Boolean value indicating if the input value was obfuscated during the transformation. The examples are: hash for Transformation and count for Aggregation. List of available methods that are considered masking is dependent on the source system.