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Determining the Right Batch Size for Deletes

Jess Pomfret breaks out the lab coat and safety goggles:

I found myself needing to clear out a large amount of data from a table this week as part of a clean up job.  In order to avoid the transaction log catching fire from a long running, massive delete, I wrote the following T-SQL to chunk through the rows that needed to be deleted in batches. The question is though, what’s the optimal batch size?

I usually go with a rule of thumb: 1K for wide tables (in terms of columns and row size) or when there are foreign key constraints, 10K for medium-width tables, and about 25K for narrow tables. But if this is an operation you run frequently, it’s worth experimenting a bit.