This script will delete rows within a table that are out-with the specified retention period. This can be useful if you’re running deletes on large tables, and particularly if;
# Deletes are taking a long time & you’re finding it difficult to track progress.
# You have a short maintenance window each day to perform such tasks, which could be due to caution over blocking/deadlocks.
# Your server is not equipped to handle the log file bloat associated with running the delete as a single transaction.
Whatever the reason is, this is a useful script to have in the toolbelt.
I’ve set this to delete 10k rows at a time, although you can find your own sweet spot.
USE [Adventureworks] GO SET NOCOUNT ON DECLARE @today_floored DATETIME, @retention_period INT, @retention_date DATETIME -- Get today, clearing time to 12:00am SET @today_floored = (SELECT DATEADD(m, DATEDIFF(m, 0, GETDATE()), 0)) --+(SELECT [rollover_time] FROM [table]) -- Set retention period (in months, unless the line above is changed) SET @retention_period = 13 -- Apply retention date deduction to floored date SELECT @retention_date = DATEADD(m, -@retention_period, @today_floored) PRINT 'Deleting data < '+ CAST(@retention_date AS VARCHAR(20)) -- Delete in batches; set preferred rowcount and enter the table/column names DECLARE @BatchSize INT = 1, @total BIGINT = 0 SET rowcount 10000 WHILE @BatchSize <> 0 BEGIN DELETE [dbo].[FactResellerSalesXL_CCI] WHERE [ShipDate] < @retention_date SET @BatchSize = @@rowcount SET @total = @total + @batchsize PRINT @total END
To find out how long it’ll take until all rows have been deleted, you could;
1. Get row counts.
2. Run deletion script for 10 minutes.
3. Check how many rows were affected.
4. Refresh Disk Usage by Top Tables report / get new counts.
5. Compare numbers above.
6. If the math works out to be 9 months before it’ll finish, then get an index added.