Tables are dropped, schemas change, views are created: lineage tracks these changes over time.
Atlas reads the content of the metadata it collects to build relationships among data assets. When Atlas receives query information, it notes the input and output of the query at the column level: Atlas generates a lineage map that traces how data is used and transformed over time. This visualization of data transformations allows governance teams to quickly identify the source of data and to understand the impact of data changes.
Atlas processes contain lineage info; data assets by themselves do not. Impala queries are represented as processes and have lineage information; the data asset affected by Impala queries appear as Hive entities.
HDFS, S3, ADLS files appear when they are referenced by Hive, Impala, or Spark queries; operations that occur on the file system are not reflected in Atlas lineage.
The contents of a lineage graph are determined by what metadata is collected from services. If a process refers to a data asset but Atlas doesn't have an entity for that data asset, Atlas isn’t able to create an entity for the process and the lineage defined by that process won’t appear in Atlas.
Deleted data assets
Entities that represent data assets that have been deleted (such as after a DROP TABLE command in Hive) are marked as deleted. They show up in search results only if the checkbox to Show historical entities is checked. Deleted entities appear in lineage graph dimmed-out.
Historical entities are never automatically removed or archived from Atlas' metadata. If you find you need to remove specific deleted entities, you can purge specific entities by their GUIDs through REST API calls.
Temporary data assets
Sometimes operations include data assets that are created and then deleted as part of the operation (or as part of a series of operations that occur close together in time). Atlas collects metadata for these temporary objects. The technical metadata for the operation, such as query text, includes a reference to the temporary object; the object itself will show in the Atlas lineage diagrams.
For example, consider a Hive pipeline that writes data to a table, transforms the data and writes it to a second table, then removes the first table. The lineage graph shows the source file, the process that creates the first table, the first table, the process that transforms the data and loads it into the second table, and the second table. Atlas also collects the process where the first table is dropped. When you view the lineage graph, you can choose to show the first table or to exclude it by setting the filter option Hide Deleted Entity.