RBAR vs Batch

Many years ago Jeff Moden (of SQL Server Central fame) came up with the concept of RBAR. Row-By-Agonizing-Row. At it’s most basic it means you are inserting one row at a time. A more broad interpretation says it’s any type of loop even the type caused by a recursive CTE.

And the point? Loops are slower than batches.

Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.

Simple example:

Batch

USE AdventureWorks2014;
GO
SELECT TOP 0 * INTO vSWA FROM Sales.vStoreWithAddresses;
GO
DECLARE @StartTime datetime = getdate()
INSERT INTO vSWA
SELECT * FROM Sales.vStoreWithAddresses;
SELECT DATEDIFF(millisecond,@StartTime,getdate())
GO
DROP TABLE vSWA;
GO
-- 23 milliseconds

RBAR

USE AdventureWorks2014;
GO
SELECT TOP 0 * INTO vSWA FROM Sales.vStoreWithAddresses;
GO

DECLARE curSWA CURSOR KEYSET FOR 
SELECT * FROM Sales.vStoreWithAddresses;

DECLARE @BusinessEntityID int
		,@Name Name
		,@AddressType Name
		,@AddressLine1 nvarchar(60)
		,@AddressLine2 nvarchar(60)
		,@City nvarchar(30)
		,@StateProvinceName Name
		,@PostalCode nvarchar(15)
		,@CountryRegionName Name;

OPEN curSWA

DECLARE @StartTime datetime = getdate();
FETCH NEXT FROM curSWA INTO @BusinessEntityID, @Name, @AddressType, @AddressLine1,
					@AddressLine2, @City, @StateProvinceName, @PostalCode,
					@CountryRegionName;
WHILE (@@fetch_status <> -1)
BEGIN
	IF (@@fetch_status <> -2)
	BEGIN
		INSERT INTO vSWA (BusinessEntityID, Name, AddressType, AddressLine1,
						AddressLine2, City, StateProvinceName, PostalCode,
						CountryRegionName)
			VALUES (@BusinessEntityID, @Name, @AddressType, @AddressLine1,
					@AddressLine2, @City, @StateProvinceName, @PostalCode,
					@CountryRegionName)
	END
	FETCH NEXT FROM curSWA INTO @BusinessEntityID, @Name, @AddressType, @AddressLine1,
					@AddressLine2, @City, @StateProvinceName, @PostalCode,
					@CountryRegionName;
END
SELECT DATEDIFF(millisecond,@StartTime,getdate());

CLOSE curSWA;
DEALLOCATE curSWA;
GO

DROP TABLE vSWA;
GO
--850

So 23 milliseconds for the batch version and 850 milliseconds for RBAR. What a difference.

Now in this case the code for the RBAR is also a lot more complicated. But that isn’t always the case. It also isn’t always the case that RBAR is slower. But it’s almost always a lot slower than batch.

So, while the code for RBAR is often easier to write, even though it might be physically longer, it’s probably going to be slower too.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.