Improve Efficiency of SQL Query (reducing Hash Match cost)

Question

I have the following SQL query that only takes 6 seconds to run, but I am trying to get it down to around 3 seconds if possible. I've noticed that there are 3 places in the Execution Plan that have pretty high costs. 1: Hash Match (partial aggregate) - 12%.
2: Hash Match (inner join) - 36%. 3: Index Scan - 15%.
I've been researching Hash Match for a couple days now, but I just don't seem to be getting it. I can't seem to figure out how to decrease the cost. I've read that OUTER APPLY is really inefficient and I have two of those in my query, but I haven't been
able to figure out a way to get the results I need without them. 
I am fairly new to SQL so I am hoping I can get some help with this.
SELECT wi.WorkItemID,
wi.WorkQueueID as WorkQueueID,
wi.WorkItemTypeID,
wi.WorkItemIdentifier,
wi.DisplayIdentifier,
wi.WorkItemStatusID,
wi.SiteID,
wi.AdditionalIdentifier,
wi.WorkQueueDescription,
wi.WorkItemTypeDescription,
wi.WorkQueueCategoryDescription,
wi.Active,
wi.CheckedOutOn,
wi.CheckedOutBy_UserID,
wi.CheckedOutBy_UserName,
wi.CheckedOutBy_FirstName,
wi.CheckedOutBy_LastName,
wi.CheckedOutBy_FullName,
wi.CheckedOutBy_Alias,
b.[Description] as BatchDescription,
bt.[Description] as BatchType,
bs.[Description] as PaymentBatchStatus,
b.PostingDate AS PostingDate,
b.DepositDate,
b.BatchDate,
b.Amount as BatchTotal,
PostedAmount = ISNULL(PostedPayments.PostedAmount, 0),
TotalPayments = ISNULL(PostedPayments.PostedAmount, 0), --Supporting legacy views
TotalVariance = b.Amount - ISNULL(PostedPayments.PostedAmount, 0), -- ISNULL(Payments.TotalPayments, 0),
PaymentsCount = ISNULL(Payments.PaymentsCount, 0),
ISNULL(b.ReferenceNumber, '') AS PaymentBatchReferenceNumber,
b.CreatedOn,
b.CreatedBy_UserID,
cbu.FirstName AS CreatedBy_FirstName,
cbu.LastName AS CreatedBy_LastName,
cbu.DisplayName AS CreatedBy_DisplayName,
cbu.Alias AS CreatedBy_Alias,
cbu.UserName AS CreatedBy_UserName,
b.LastModifiedOn,
b.LastModifiedBy_UserID,
lmbu.FirstName AS LastModifiedBy_FirstName,
lmbu.LastName AS LastModifiedBy_LastName,
lmbu.DisplayName AS LastModifiedBy_DisplayName,
lmbu.Alias AS LastModifiedBy_Alias,
lmbu.UserName AS LastModifiedBy_UserName,
0 AS VisitID, --Payment work items are not associated with VisitID, but it is a PK field on all the Work Queue view models...for now...
0 AS RCMPatientID, --Payment work items are not associated with RCMPatientID, but it is a PK field on all the Work Queue view models...for now...
0 AS PatientID
FROM Account.PaymentBatch AS b (NOLOCK)
INNER JOIN ViewManager.WorkItems AS wi (NOLOCK)
ON wi.WorkitemIdentifier = b.PaymentBatchID
AND wi.WorkItemTypeID = 3
INNER JOIN Account.PaymentBatchStatus AS bs (NOLOCK)
ON b.PaymentBatchStatusID = bs.PaymentBatchStatusID
LEFT JOIN Account.PaymentBatchType bt (NOLOCK)
ON b.PaymentBatchTypeID = bt.PaymentBatchTypeID
INNER JOIN ViewManager.[User] AS cbu (NOLOCK)
ON b.CreatedBy_UserID = cbu.UserID
INNER JOIN ViewManager.[User] AS lmbu (NOLOCK)
ON b.LastModifiedBy_UserID = lmbu.UserID
LEFT JOIN (
SELECT p.PaymentBatchID
, SUM(p.Amount) AS TotalPayments
, COUNT(0) AS PaymentsCount
FROM Account.Payment AS p (NOLOCK)
WHERE p.PaymentTypeID = 1
AND ISNULL(p.Voided, 0) = 0
GROUP BY p.PaymentBatchID
) AS Payments ON b.PaymentBatchID = Payments.PaymentBatchID
LEFT JOIN (
SELECT p.PaymentBatchID
, SUM(pa.Amount) AS PostedAmount
FROM Account.Payment AS p (NOLOCK)
INNER JOIN Account.PaymentAllocation AS PA (NOLOCK)
ON p.PaymentID = pa.PaymentID
AND (pa.AllocationTypeID = 101 OR pa.AllocationTypeID = 111)
WHERE p.PaymentTypeID = 1
AND ISNULL(p.Voided, 0) = 0
GROUP BY p.PaymentBatchID
) AS PostedPayments ON b.PaymentBatchID = PostedPayments.PaymentBatchID
OUTER APPLY (
SELECT
P.PaymentBatchID,
SUM(CASE WHEN P.PaymentTypeID = 1 THEN 1 ELSE 0 END) as PaymentsCount --only count regular payments not adjustments
FROM
Account.Payment p (NOLOCK)
WHERE
p.PaymentBatchID = b.PaymentBatchID
AND p.PaymentTypeID IN (1,2) AND ISNULL(p.Voided, 0)= 0
GROUP BY
P.PaymentBatchID
) payments
OUTER APPLY (
SELECT
P.PaymentBatchID,
SUM(pa.Amount) as PostedAmount
FROM
Account.PaymentAllocation pa (NOLOCK)
INNER JOIN
Account.Payment p (NOLOCK) ON pa.PaymentID = p.PaymentID
INNER JOIN
Account.AllocationType t (NOLOCK) ON pa.AllocationTypeID = t.AllocationTypeID
WHERE
p.PaymentBatchID = b.PaymentBatchID
AND p.PaymentTypeID IN (1,2)
AND ISNULL(p.Voided, 0)= 0
--AND (t.Credit = 0
--OR (t.Credit <> 0 And Offset_PaymentAllocationID IS NULL AND (SELECT COUNT(1) FROM Account.paymentAllocation pa2 (NOLOCK)
-- WHERE pa2.PaymentID = pa.PaymentID AND pa2.AllocationTypeID IN (101, 111)
-- AND pa2.Offset_PaymentAllocationID IS NULL) > 0))
GROUP BY
P.PaymentBatchID
) PostedPayments

Answer 1

The percentages you see are only estimates and may not necessarily not reflect where the real bottleneck is. Particularly, if it is due to a misestimate somewhere.
To be able to help you improve the performance, we need to see the CREATE TABLE and CREATE INDEX statements for the tables. We also need to see the actual query plan. (In XML format, not a screen shot.) Posting all this here is not practical, but you could
upload it somewhere. (Dropbox, Google Drive etc.)
Be very careful with the NOLOCK hint. Using the NOLOCK hint casually lead to transient erratic behaviour which is very difficult to understand. Using it consistenly through a query like you do, is definitely bad practice.
Erland Sommarskog, SQL Server MVP, [email protected]