Crawler
The policy that specifies update and delete behaviors for the crawler. The policy tells the crawler what to do in the event that it detects a change in a table that already exists in the customer's database at the time of the crawl. The SchemaChangePolicy does not affect whether or how new tables and partitions are added. New tables and partitions are always created regardless of the SchemaChangePolicy on a crawler. The SchemaChangePolicy consists of two components, UpdateBehavior and DeleteBehavior.
Properties
The deletion behavior when the crawler finds a deleted object. A value of LOG specifies that if a table or partition is found to no longer exist, do not delete it, only log that it was found to no longer exist. A value of DELETE_FROM_DATABASE specifies that if a table or partition is found to have been removed, delete it from the database. A value of DEPRECATE_IN_DATABASE specifies that if a table has been found to no longer exist, to add a property to the table that says 'DEPRECATED' and includes a timestamp with the time of deprecation.
The update behavior when the crawler finds a changed schema. A value of LOG specifies that if a table or a partition already exists, and a change is detected, do not update it, only log that a change was detected. Add new tables and new partitions (including on existing tables). A value of UPDATE_IN_DATABASE specifies that if a table or partition already exists, and a change is detected, update it. Add new tables and partitions.