Problem optimizing sql query with cross apply sub query - sql

Question

So I have three tables:
MakerParts, that holds the primary information of a Vehicle Part:
Id
MakerId
PartNumber
Description
1
1
ABC1234
Tire
2
1
XYZ1234
Door
MakerPrices, that holds the price history variation for the parts (references MakerParts.Id on MakerPartNumberId, and the table MakerPriceUpdates on UpdateId):
Id
MakerPartNumberId
UpdateId
Price
1
1
1
9.83
2
1
2
11.23
MakerPriceUpdates, that holds the date of prices updates. This update is basically a CSV file that is uploaded to our system. One file, one line on this table, multiple prices changes on the table MakerPrices.
Id
Date
FileName
1
2019-01-09 00:00:00.000
temp.csv
2
2019-01-11 00:00:00.000
temp2.csv
This means that one part (MakerParts) may have multiple prices (MakerPrices). The date of the price change is on the table MakerPricesUpdates.
I want to select all MakerParts where the most recent price is zero, filtering by the MakerId on table MakerParts.
What I've tried:
select mp.* from MakerParts mp cross apply
(select top 1 Price from MakerPrices inner join
MakerPricesUpdates on MakerPricesUpdates.Id = MakerPrices.UpdateId where
MakerPrices.MakerPartNumberId = mp.Id order by Date desc) as p
where mp.MakerId = 1 and p.Price = 0
But that is absurdly slow (we have about 100 million lines on the MakerPrices table). I'm having a hard time optimizing this query. (the result is only two rows for the MakerId 1, and it took 2 mins to run). I also tried:
select * from (
select
mp.*,
(select top 1 Price from MakerPrices inner join
MakerPricesUpdates on MakerPricesUpdates.Id = MakerPrices.UpdateId
where MakerPrices.MakerPartNumberId = mp.Id order by Date desc) as Price
from MakerParts mp) as temp
where temp.Price = 0 and MakerId = 1
Same result, and same time. My query plan (for the first query) (no new indexes suggested by Management Studio):

Answer 1

I think you can avoid joining MakerPriceUpdates with makerprices since with the highest
UpdateId you can find the latest price updates. It will save you some time.
select mp.* from MakerParts mp cross apply
(select top 1 Price from MakerPrices where
MakerPrices.MakerPartNumberId = mp.Id order by MakerPrices.UpdateId desc) as p
where mp.MakerId = 1 and p.Price = 0
You can further reduced some times by avoiding sort and order by with cte and row_number() as below:
;with LatestMakerPrices as
(
select *,row_number()over(partition by MakerPartNumberId order by updateid desc)rn from MakerPrices
)
select mp.* from MakerParts mp cross apply
(select price from LatestMakerPrices lmp where lmp.MakerPartNumberId=mp.Id) as p
where mp.MakerId = 1 and p.Price = 0
Execution plan difference between query in question and my answer:

Answer 2

try:
WITH tab AS (
SELECT *, NULL as Price FROM MakerParts
WHERE not exists (
SELECT Id
FROM MakerPrices
WHERE MakerPrices.MakerPartNumberId = MakerParts.Id
)
)
SELECT * from tab WHERE MakerId = 2
UNION ALL
SELECT a.* , Price
FROM [dbo].[MakerParts] a
LEFT JOIN [dbo].[MakerPrices] b
ON b.MakerPartNumberId = a.Id
WHERE MakerId = 2 AND Price = 0

Answer 3

Try your query:
select mp.* from MakerParts mp cross apply
(select top 1 Price from MakerPrices inner join
MakerPricesUpdates on MakerPricesUpdates.Id = MakerPrices.UpdateId where
MakerPrices.MakerPartNumberId = mp.Id order by Date desc) as p
where mp.MakerId = 1 and p.Price = 0
After creating below index:
CREATE NONCLUSTERED INDEX [NCIdx_MakerPrices_MakerPartNumberId_UpdateId] ON [dbo].[MakerPrices]
(
[MakerPartNumberId] ASC,
[UpdateId] ASC
)
INCLUDE([Price])
And making ID column of MakerPricesUpdates table primary key.