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  • Deleting 1 millions rows in SQL Server

    Deleting 1 millions rows in SQL Server

    I am working on a client's database and there is about 1 million rows that need to be deleted due to a bug in the software. Is there an efficient way to delete them besides:

    DELETE FROM table_1 where condition1 = 'value' ?
    

    回答1

    Here is a structure for a batched delete as suggested above. Do not try 1M at once...

    The size of the batch and the waitfor delay are obviously quite variable, and would depend on your servers capabilities, as well as your need to mitigate contention. You may need to manually delete some rows, measuring how long they take, and adjust your batch size to something your server can handle. As mentioned above, anything over 5000 can cause locking (which I was not aware of).

    This would be best done after hours... but 1M rows is really not a lot for SQL to handle. If you watch your messages in SSMS, it may take a while for the print output to show, but it will after several batches, just be aware it won't update in real-time.

    Edit: Added a stop time @MAXRUNTIME & @BSTOPATMAXTIME. If you set @BSTOPATMAXTIME to 1, the script will stop on it's own at the desired time, say 8:00AM. This way you can schedule it nightly to start at say midnight, and it will stop before production at 8AM.

    Edit: Answer is pretty popular, so I have added the RAISERROR in lieu of PRINT per comments.

    DECLARE @BATCHSIZE INT, @WAITFORVAL VARCHAR(8), @ITERATION INT, @TOTALROWS INT, @MAXRUNTIME VARCHAR(8), @BSTOPATMAXTIME BIT, @MSG VARCHAR(500)
    SET DEADLOCK_PRIORITY LOW;
    SET @BATCHSIZE = 4000
    SET @WAITFORVAL = '00:00:10'
    SET @MAXRUNTIME = '08:00:00' -- 8AM
    SET @BSTOPATMAXTIME = 1 -- ENFORCE 8AM STOP TIME
    SET @ITERATION = 0 -- LEAVE THIS
    SET @TOTALROWS = 0 -- LEAVE THIS
    
    WHILE @BATCHSIZE>0
    BEGIN
        -- IF @BSTOPATMAXTIME = 1, THEN WE'LL STOP THE WHOLE JOB AT A SET TIME...
        IF CONVERT(VARCHAR(8),GETDATE(),108) >= @MAXRUNTIME AND @BSTOPATMAXTIME=1
        BEGIN
            RETURN
        END
    
        DELETE TOP(@BATCHSIZE)
        FROM SOMETABLE
        WHERE 1=2
    
        SET @BATCHSIZE=@@ROWCOUNT
        SET @ITERATION=@ITERATION+1
        SET @TOTALROWS=@TOTALROWS+@BATCHSIZE
        SET @MSG = 'Iteration: ' + CAST(@ITERATION AS VARCHAR) + ' Total deletes:' + CAST(@TOTALROWS AS VARCHAR)
        RAISERROR (@MSG, 0, 1) WITH NOWAIT
        WAITFOR DELAY @WAITFORVAL 
    END
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  • 原文地址:https://www.cnblogs.com/chucklu/p/14921520.html
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