When Deletes Increase Data Size

Brent Ozar shows a case where indexes can grow in size as you delete data:

Here’s one way that deletes can cause a table to grow:
– The rows were originally written when the database didn’t have Read Committed Snapshot (RCSI), Snapshot Isolation (SI), or Availability Groups (AGs) enabled
– RCSI or SI was enabled, or the database was added into an Availability Group
– During the deletions, a 14-byte timestamp was added to each deleted row to support RCSI/SI/AG reads

Click through for a demo and takeaways.

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