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D.4  Reset Cluster and Delete From Cluster

The RESET CLUSTER clustername statement resets all values in the current cluster row (or the entire cluster, if applicable) to nulls and zeros. However, it does not remove the row, meaning the row remains in place but with cleared values. When new rows are added, this reset row is not reused. This statement also works for scalar clusters.

In contrast, the DELETE FROM CLUSTER clustername statement removes the current row entirely, making it available for reuse when new rows are added. This deletion affects the cluster's ordering, meaning the rows may no longer maintain their original order. To remove all rows from a cluster — commonly used when reloading data — use: delete from cluster xxx: all where xxx is the cluster name.


Note: The DELETE FROM CLUSTER statement works by removing the current row and replacing its data with the data from the last row in the cluster. The cluster's size is then reduced by one.

Advantages:
  1. Prevents Fragmentation: Prevents gaps in cluster rows by keeping the cluster compact, ensuring efficient memory use.
  2. Reduces Overhead: Moves only one row instead of shifting multiple rows, making deletion operations very faster.
  3. Optimized for Frequent Adds/Deletes: Keeps space immediately reusable, making it ideal for dynamic datasets.

Summary table

Operation Effect Reusability Impact on Cluster
RESET CLUSTER Sets values in the row to nulls and zeros Row remains but is not reused Keeps order intact
DELETE FROM CLUSTER Removes the row entirely Row space is reused Last row replaces deleted row, affecting order
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