SQL Server transaction fails and table gets locked - sql

Question

My stored procedure is like this
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[Bid_Create]
#BidType int,
#ClientId int,
#BidDate date,
#EmailNotificationStatus int,
#BidStatus int,
#BidAmount int,
#ProductId int
AS
DECLARE #highestBid int;
BEGIN
BEGIN TRY
BEGIN TRANSACTION
SET NOCOUNT ON;
SET #highestBid = (SELECT Max(wf_bid.BidAmount) AS HighestBitAmount
FROM wf_bid
WHERE wf_bid.ProductId = #ProductId)
IF #highestBid is NULL OR #highestBid < #BidAmount
BEGIN
UPDATE wf_bid
SET BidStatus = '1'
WHERE Id = (SELECT TOP 1 id
FROM [wf_bid]
WHERE BidAmount = (SELECT MAX(BidAmount)
FROM [wf_bid]
WHERE ProductId = #ProductId
AND ClientId = #ClientId))
INSERT INTO wf_bid (BidType, ClientId, BidDate, EmailNotificationStatus, BidStatus)
VALUES (#BidType, #ClientId, #BidDate, #EmailNotificationStatus, #BidStatus)
END
COMMIT TRANSACTION
END TRY
BEGIN CATCH
ROLLBACK TRANSACTION
END CATCH
END
Everything looks okay to me. But once I run this, table is getting locked. No other query on the table works (I think it is because transaction is not getting committed).
Can anyone point out what is wrong with this query? And how can I unlock the table?

Answer 1

But once I run this, table is getting locked
This may be due to update taking many locks,which in turn may be due to predicate not being sargable. Though this update locks(U) lock will be released as soon as the predicate is not matched.You will experience blocking
One more reason ,why this update may block your whole table is when this transaction acquires more than 5000 locks..
another reason can be when your transaction fails after committing so many rows and it has to do a lot of rollback work
Above are the reasons ,i could think of,where you can experience table is locked feeling
to troubleshoot that,you will need to check lockings blokcings using below query
select resource_type,resource_Database_id,
request_mode,request_type,request_Status,request_session_id
from sys.dm_tran_locks
where request_session_id=<<your update session id>>
also you are accessing table many times,for getting max.you can rewrite it like below
;with cte
as
(
select top (1) with ties id,bidstatus from
wf_bid
where ProductId=#ProductId and ClientId=#ClientId)
order by
row_number() over (partition by id order by bid_Amount desc)
)
update cte
set bidstatus=1