Question

I am a very beginner with sql and I need to write a SP in order to increment products views count. When user searches on site we want to increment the counter for all products that were returned by search. I see two problems with my SP:

1. it uses cursor
2. it starts a lot of transactions

The SP is called simultaneous by many threads. After I implemented it I got many timeout exceptions. My count table looks like this:

ProductsViewsCount(ProductId int, Timestamp datetime, ViewType int, Count int)

Tiemstamp column is rounded to the closest hour in .net code that calls the SP. Basically I will count the views by hour.

The SP looks like this:

    CREATE PROCEDURE [dbo].[IncrementProductsViews]
    -- Add the parameters for the stored procedure here
    @ProductsIds as varchar(max) = '', --CSV ids of products that were returned by search
    @ViewType int,
    @Timestamp datetime
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    DECLARE @id int 
    DECLARE idsCursor CURSOR FOR 
        SELECT Data FROM dbo.Split(@ProductsIds,',')

    OPEN idsCursor
    FETCH NEXT FROM idsCursor INTO @id
    WHILE @@FETCH_STATUS = 0
    BEGIN
        BEGIN TRAN
            UPDATE dbo.ProductsViewsCount SET Count = Count + 1 
                WHERE ProductId = @id AND ViewType = @ViewType AND Timestamp = @Timestamp
            if @@rowcount = 0
            BEGIN
                INSERT INTO dbo.ProductsViewsCount (ProductId, Timestamp, ViewType, Count) 
                    VALUES (@id, @Timestamp, @ViewType, 1)
            END
        COMMIT TRAN     
        FETCH NEXT FROM idsCursor INTO @id
    END     
    CLOSE idsCursor   
    DEALLOCATE idsCursor
    select 1
END

Can I do this in a more efficient manner?

Answer 1

You can do it on a set operation instead of a cursor:

CREATE PROCEDURE [dbo].[IncrementProductsViews]
    -- Add the parameters for the stored procedure here
    @ProductsIds as varchar(max) = '', --CSV ids of products that were returned by search
    @ViewType int,
    @Timestamp datetime
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    ;WITH CTE AS
    (
        SELECT *
        FROM dbo.ProductsViewsCount
        WHERE ViewType = @ViewType AND [Timestamp] = @Timestamp
    )


    MERGE CTE AS A
    USING (SELECT * FROM dbo.Split(@ProductsIds,',')) B
    ON A.ProductId = B.Data 
    WHEN MATCHED THEN UPDATE SET A.[Count] = B.[Count] + 1
    WHEN NOT MATCHED BY TARGET THEN
    INSERT(ProductId, [Timestamp], ViewType, [Count])
    VALUES(Data, @Timestamp, @ViewType, 1);

    SELECT 1 -- I don't know why this is here
END