A Delta table in Unity Catalog is partitioned by event_date and is queried mostly by customer_id, which filters poorly because it is not a partition column. The team decides to move the table to liquid clustering on customer_id and event_date, and recreates it with the statement below. Which two statements correctly describe what liquid clustering means for the new table? (Select TWO.)
CREATE OR REPLACE TABLE prod.events.page_views
CLUSTER BY (customer_id, event_date)
AS SELECT * FROM prod.events.page_views_legacy;- AA table that uses liquid clustering cannot also declare partition columns, which is why the move required the table to be recreated rather than altered in place. Correct
- BClustering keys are fixed at table creation, so a later change in the team's query filters would require the table to be recreated and reloaded from the source data.
- CClustering keys can be revised later with an ALTER TABLE statement carrying a new CLUSTER BY clause, and files already written stay as they are until a later OPTIMIZE run. Correct
- DZ-ordering should be applied over the same two columns during each OPTIMIZE run, so that data skipping keeps working alongside the declared clustering keys.
- EEach clustering key must be a generated column derived from the ingest timestamp, so that the resulting layout follows the order in which the rows arrived at the table.
Why A is correct: Liquid clustering and Hive style partitioning are alternative layout strategies on a Delta table, and clustering cannot be added to a table that already carries partition columns.
Why B is wrong: This is tempting because partition columns really are fixed for the life of a table, but clustering keys are deliberately not: they can be redeclared at any time.
Why C is correct: Redeclaring the keys changes the layout that future writes and future OPTIMIZE runs target; it does not rewrite history at the moment the statement is issued.
Why D is wrong: It sounds like belt and braces, but ZORDER BY is not supported on a liquid clustered table; the clustering keys are what OPTIMIZE uses to lay the data out.
Why E is wrong: Generated columns are a real Delta feature often used with partitioning, which makes this plausible, but liquid clustering places no such requirement on its keys.