topic Re: time travel with DLT in Get Started Discussions

time travel with DLT

leelee3000 — Thu, 14 Dec 2023 14:30:22 GMT

Needed some help with Time Travel with Delta Live tables

We were trying to figure out if we can go in and alter the history on this table, and what would happen to data that we mass upload? By this we mean we have data from the past that we would like to upload, and were wondering what the Time Travel information would look like for that.

Our concern is that since it already happened and potentially schema changes took place, data was updated etc how would that look within the Delta Live tables and its time travel output. #deltalivetables #DLT #timetravel

Re: time travel with DLT

leelee3000 — Thu, 14 Dec 2023 14:50:36 GMT

I'm assuming Time Travel in Delta Lake doesn't allow you to change historical data versions?

Re: time travel with DLT

Louis_Frolio — Thu, 14 Dec 2023 14:50:57 GMT

Delta Live Tables leverage Delta Lake, or Delta Tables. Delta tables, through transactions (e.g. insert, update, delete, merges, optimization) create versions of said Delta Table. Once a version is created it cannot be altered, it is immutable. You can always roll back (restore) to an ealier version of the Delta table, this action will create a new version of the table. The older versions will always be present unless vacuum is run.

Hope this helps.

Louis