In Amazon Redshift, if a table is used for both delivery and updates, do you need to run VACUUM to maintain performance?
💡 Model Answer
Yes, running VACUUM is often necessary in Redshift when a table experiences frequent updates or deletes. Redshift stores data in columnar blocks; updates are implemented as a delete followed by an insert, leaving orphaned rows that consume space and degrade query performance. VACUUM reclaims space and reorders rows to improve compression and query speed. The decision to vacuum depends on the workload:
- High update/delete rate: schedule a VACUUM after peak write windows or use a nightly job.
- Read-heavy, write-light: a full VACUUM may be unnecessary; a VACUUM SORT only can be used to maintain sort order.
- Large tables: use VACUUM DELETE ONLY to reclaim space without sorting.
Additionally, enable automatic vacuuming via Redshift’s maintenance window or use the VACUUM command with SORTKEY to keep data sorted for faster scans. Monitoring the pg_table_def and stv_blocklist views helps determine when a vacuum is needed. Thus, for a table that serves both delivery and updates, a scheduled VACUUM is recommended to keep performance optimal.
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