Performing bulk deletion in very large, high-volume PostgreSQL tables quickly and efficiently can be achieved through several strategies:

1. Batch Deletion:
   • Method: Delete records in smaller batches (e.g., 10,000 rows at a time).
   • Benefits: Reduces the load on the transaction log, minimizes locking, and helps in managing resources effectively.
2. Use of Indexes:
   • Method: Ensure deletion criteria are indexed to speed up the deletion process.
   • Benefits: Significantly reduces the time to find rows to be deleted.
3. Temporary Disabling of Indexes:
   • Method: Disable non-critical indexes temporarily during bulk deletion.
   • Benefits: Increases deletion speed as the database won't have to update indexes during deletion.
4. Table Partitioning:
   • Method: Use partitioned tables and drop entire partitions if applicable.
   • Benefits: Dropping a partition is much faster than deleting rows and is effective for deleting large contiguous datasets.
5. Avoid Cascade Deletes:
   • Method: Structure deletions to avoid cascading to related tables unless necessary.
   • Benefits: Reduces the complexity and time of deletion operations.
6. Post-Deletion Vacuuming:
   • Method: Run VACUUM FULL after deletion to reclaim space.
   • Benefits: Helps in reclaiming disk space and updating statistics, thus maintaining database performance.
7. Schedule During Off-Peak Hours:
   • Method: Perform deletion tasks during periods of low activity.
   • Benefits: Minimizes impact on database performance and user experience.
8. Monitoring:
   • Method: Monitor system performance during deletion.
   • Benefits: Allows for adjustments in batch size or pauses in the operation to mitigate performance impacts.

These strategies, when applied thoughtfully, can lead to efficient management of bulk deletion operations in large-scale PostgreSQL environments. Remember to always backup critical data before performing bulk deletions.