Databricks-Certified-Professional-Data-Engineer Exam Dumps : Databricks Certified Data Engineer Professional Exam

The Tungsten encoding used by Databricks is optimized for storing string data; newly-added native support for querying JSON strings means that string types are always most efficient.

Because Delta Lake uses Parquet for data storage, data types can be easily evolved by just modifying file footer information in place.

Human labor in writing code is the largest cost associated with data engineering workloads; as such, automating table declaration logic should be a priority in all migration workloads.

Because Databricks will infer schema using types that allow all observed data to be processed, setting types manually provides greater assurance of data quality enforcement.

Schema inference and evolution on .Databricks ensure that inferred types will always accurately match the data types used by downstream systems.

It marks a column as having low enough cardinality to properly map distinct values to available partitions, allowing a broadcast join.

It marks a column as small enough to store in memory on all executors, allowing a broadcast join.

It caches a copy of the indicated table on attached storage volumes for all active clusters within a Databricks workspace.

It marks a DataFrame as small enough to store in memory on all executors, allowing a broadcast join.

It caches a copy of the indicated table on all nodes in the cluster for use in all future queries during the cluster lifetime.

Because the vacuum command permanently deletes all files containing deleted records, deleted records may be accessible with time travel for around 24 hours.

Because the default data retention threshold is 24 hours, data files containing deleted records will be retained until the vacuum job is run the following day.

Because Delta Lake time travel provides full access to the entire history of a table, deleted records can always be recreated by users with full admin privileges.

Because Delta Lake's delete statements have ACID guarantees, deleted records will be permanently purged from all storage systems as soon as a delete job completes.

Because the default data retention threshold is 7 days, data files containing deleted records will be retained until the vacuum job is run 8 days later.