I have this query running around 15 seconds on my system. The query plan is here. I believe the main problem is around here, where the optimizer chooses nested loops and is mistaken with cardinality:
Tables _Reference65215 and _InfoRg100966 have 454 and 3332 rows respectively.
If I force SQL Server to use hash match here the execution time drops to 2 seconds.
I cannot use any kind of hints here as the code comes from the platform. The platform uses its own language which then gets interpreted to T-SQL. I can change the query. Stats are up to date. Maxdop 1 is a general recommendation from the vendor of the platform
What might be the reason of choosing nested loops and how to fix it? Maybe there is something else that is worth attention?
EXEC sp_executesql
N'SELECT TOP 45 T1._IDRRef,
T1._Marked,
T1._Number,
T1._Date_Time,
T1._Posted,
T1._Fld74271RRef,
CASE
WHEN T1._Fld74272RRef=@P1
THEN T1._Fld74307RRef
ELSE T1._Fld74272RRef
END,
T1._Fld74273,
T1._Fld74274RRef,
T1._Fld74281,
CASE
WHEN T1._Fld74272RRef=@P2
THEN 0x000100DD
WHEN T1._Fld74272RRef=@P3
OR T1._Fld74272RRef=@P4
OR T1._Fld74272RRef=@P5
THEN 0x0000FF7E
ELSE 0x0000FF3E
END,
CASE
WHEN T1._Fld74272RRef=@P6
THEN T1._Fld74284RRef
WHEN T1._Fld74272RRef=@P7
OR T1._Fld74272RRef=@P8
OR T1._Fld74272RRef=@P9
THEN T1._Fld74285RRef
ELSE T1._Fld74282RRef
END,
T1._Fld74289RRef,
T1._Fld74303,
CASE
WHEN T1._Fld74333RRef IN( SELECT TOP 1 T12._IDRRef
AS Q_001_F_000RRef
FROM dbo._Reference65527 T12
WHERE T12._Fld67386=@P10
ORDER BY T12._Fld124008 )
THEN @P11
WHEN T1._Fld74333RRef IN( SELECT TOP 1 T13._IDRRef
AS Q_002_F_000RRef
FROM dbo._Reference65527 T13
WHERE T13._Fld67386=@P12
ORDER BY T13._Fld124008 DESC )
THEN @P13
ELSE @P14
END,
CASE
WHEN ISNULL( CAST( T2.Fld109931Balance_ AS NUMERIC(27, 2) ), @P15 )<=@P16
AND T1._Posted=0x01
AND T1._Fld74271RRef<>@P17
THEN 0x01
ELSE 0x00
END,
CASE
WHEN T11._Fld101929 IS NULL
THEN @P18
WHEN T11._Fld101929=0x01
THEN @P19
ELSE @P20
END
FROM dbo._Document65911 T1
LEFT OUTER JOIN
(
SELECT T3._Fld109927_TYPE
AS Fld109927_TYPE,
T3._Fld109927_RTRef
AS Fld109927_RTRef,
T3._Fld109927_RRRef
AS Fld109927_RRRef,
CAST( SUM( T3._Fld109931 ) AS NUMERIC(27, 2) )
AS Fld109931Balance_
FROM dbo._AccumRgT109935 T3
WHERE T3._Fld67386=@P21
AND EXISTS
(
SELECT 0x01
AS Q_001_F_000_
FROM dbo._Reference65291 T4
INNER JOIN
dbo._Reference65215 T5
ON T4._Fld118298=@P22
AND EXISTS
(
SELECT 0x01
AS Q_004_F_000_
FROM dbo._InfoRg107349 T6
WHERE T6._Fld67386=@P23
AND T6._Fld107350RRef=T4._IDRRef
AND T6._Fld107351RRef=T5._IDRRef
)
AND T5._IDRRef IN
(
SELECT T7._Reference65215_IDRRef
AS Q_005_F_000RRef
FROM dbo._Reference65215_VT116326 T7
INNER JOIN
dbo._InfoRg106545 T8
ON T8._Fld106547_TYPE=0x08
AND T8._Fld106547_RTRef=0x0000FFD5
AND T8._Fld106547_RRRef=@P24
AND T8._Fld106546_TYPE=T7._Fld116328_TYPE
AND T8._Fld106546_RTRef=T7._Fld116328_RTRef
AND T8._Fld106546_RRRef=T7._Fld116328_RRRef
WHERE T7._Fld67386=@P25
AND T8._Fld67386=@P26
)
WHERE T5._Fld67386=@P27
AND 0x08<>0x01
AND CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_002_F_000_
FROM dbo._InfoRg100966 T9
WHERE T9._Fld67386=@P28
AND T9._Fld100967RRef=T5._IDRRef
AND T9._Fld100968_TYPE=0x08
AND T9._Fld100968_RTRef=0x0000FF7E
AND T9._Fld100968_RRRef=T3._Fld109930RRef
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_003_F_000_
FROM dbo._InfoRg100973 T10
WHERE T10._Fld67386=@P29
AND T10._Fld100974RRef=T5._IDRRef
AND T10._Fld100975_TYPE=0x08
AND T10._Fld100975_RTRef=0x0000FF7E
AND T10._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END
)
AND T3._Period=@P30
AND T3._Fld109931<>@P31
AND T3._Fld109931<>@P32
GROUP BY T3._Fld109927_TYPE,
T3._Fld109927_RTRef,
T3._Fld109927_RRRef
HAVING CAST( SUM( T3._Fld109931 ) AS NUMERIC(27, 2) )<>0.0
) T2
ON T2.Fld109927_TYPE=0x08
AND T2.Fld109927_RTRef=0x00010177
AND T2.Fld109927_RRRef=T1._IDRRef
LEFT OUTER JOIN
dbo._InfoRg101927 T11
ON(0x08=T11._Fld101928_TYPE
AND 0x00010177=T11._Fld101928_RTRef
AND T1._IDRRef=T11._Fld101928_RRRef)
AND T11._Fld67386=@P33
WHERE T1._Fld67386=@P34
AND EXISTS
(
SELECT 1
FROM
(
SELECT 1
AS SDBL_DUMMY
) SDBL_DUAL
LEFT OUTER JOIN
dbo._Document65911_VT74348 T14
ON T1._IDRRef=T14._Document65911_IDRRef
AND T14._Fld67386=T1._Fld67386
LEFT OUTER JOIN
dbo._Reference65239 T15
ON T1._Fld74344_TYPE=0x08
AND T1._Fld74344_RTRef=0x0000FED7
AND T1._Fld74344_RRRef=T15._IDRRef
AND T15._Fld67386=@P35
LEFT OUTER JOIN
dbo._Reference65757 T16
ON T1._Fld74284RRef=T16._IDRRef
AND T16._Fld67386=@P36
WHERE EXISTS
(
SELECT 0x01
AS Q_001_F_000_
FROM dbo._Reference65291 T17
INNER JOIN
dbo._Reference65215 T18
ON T17._Fld118298=@P37
AND EXISTS
(
SELECT 0x01
AS Q_015_F_000_
FROM dbo._InfoRg107349 T19
WHERE T19._Fld67386=@P38
AND T19._Fld107350RRef=T17._IDRRef
AND T19._Fld107351RRef=T18._IDRRef
)
AND T18._IDRRef IN
(
SELECT T20._Reference65215_IDRRef
AS Q_016_F_000RRef
FROM dbo._Reference65215_VT116326 T20
INNER JOIN
dbo._InfoRg106545 T21
ON T21._Fld106547_TYPE=0x08
AND T21._Fld106547_RTRef=0x0000FFD5
AND T21._Fld106547_RRRef=@P39
AND T21._Fld106546_TYPE=T20._Fld116328_TYPE
AND T21._Fld106546_RTRef=T20._Fld116328_RTRef
AND T21._Fld106546_RRRef=T20._Fld116328_RRRef
WHERE T20._Fld67386=@P40
AND T21._Fld67386=@P41
)
LEFT OUTER JOIN
dbo._Reference65493 T22
ON @P42=T22._IDRRef
AND T22._Fld67386=@P43
WHERE T18._Fld67386=@P44
AND 0x08<>0x01
AND CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_002_F_000_
FROM dbo._InfoRg100966 T23
WHERE T23._Fld67386=@P45
AND T23._Fld100967RRef=T18._IDRRef
AND T23._Fld100968_TYPE=0x08
AND T23._Fld100968_RTRef=0x0000FF7E
AND T23._Fld100968_RRRef=T1._Fld74270RRef
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_003_F_000_
FROM dbo._InfoRg100973 T24
WHERE T24._Fld67386=@P46
AND T24._Fld100974RRef=T18._IDRRef
AND T24._Fld100975_TYPE=0x08
AND T24._Fld100975_RTRef=0x0000FF7E
AND T24._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END
AND 0x08<>0x01
AND NOT(NOT EXISTS
(
SELECT 0x01
AS Q_004_F_000_
FROM dbo._InfoRg99652 T25
WHERE T25._Fld67386=@P47
AND T25._Fld99653_TYPE=0x08
AND T25._Fld99653_RTRef=0x0000FFD5
AND T25._Fld99653_RRRef=T1._Fld74289RRef
AND T25._Fld99654_TYPE=0x08
AND T25._Fld99654_RTRef=0x0000FFD5
AND T25._Fld99654_RRRef=@P48
)
AND NOT CASE
WHEN EXISTS
(
SELECT top 356165165156165165 0x01
AS Q_005_F_000_
FROM dbo._InfoRg100966 T26
INNER JOIN ---------------------------------------------------------------------------
dbo._InfoRg99652 T27
ON T26._Fld100967RRef=T18._IDRRef
AND T26._Fld100968_TYPE=T27._Fld99654_TYPE
AND T26._Fld100968_RTRef=T27._Fld99654_RTRef
AND T26._Fld100968_RRRef=T27._Fld99654_RRRef
AND T27._Fld99653_TYPE=0x08
AND T27._Fld99653_RTRef=0x0000FFD5
AND T27._Fld99653_RRRef=T1._Fld74289RRef
WHERE T26._Fld67386=@P49
AND T27._Fld67386=@P50
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_006_F_000_
FROM dbo._InfoRg100973 T28
WHERE T28._Fld67386=@P51
AND T28._Fld100974RRef=T18._IDRRef
AND T28._Fld100975_TYPE=0x08
AND T28._Fld100975_RTRef=0x0000FFD5
AND T28._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END)
AND 0x08<>0x01
AND CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_007_F_000_
FROM dbo._InfoRg100966 T29
WHERE T29._Fld67386=@P52
AND T29._Fld100967RRef=T18._IDRRef
AND T29._Fld100968_TYPE=0x08
AND T29._Fld100968_RTRef=0x000106FA
AND T29._Fld100968_RRRef=T1._Fld74272RRef
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_008_F_000_
FROM dbo._InfoRg100973 T30
WHERE T30._Fld67386=@P53
AND T30._Fld100974RRef=T18._IDRRef
AND T30._Fld100975_TYPE=0x08
AND T30._Fld100975_RTRef=0x000106FA
AND T30._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END
AND CASE
WHEN T1._Fld74272RRef=@P54
OR T1._Fld74272RRef=@P55
THEN CASE
WHEN CASE
WHEN T14._Fld74350RRef IS NULL
THEN 0x01
ELSE CASE
WHEN T14._Fld74350RRef IS NOT NULL
THEN 0x08
END
END<>0x01
THEN 0x01
ELSE 0x00
END
WHEN T1._Fld74272RRef=@P56
THEN CASE
WHEN 0x08<>0x01
THEN 0x01
ELSE 0x00
END
ELSE 0x01
END=0x01
AND CASE
WHEN T1._Fld74272RRef=@P57
OR T1._Fld74272RRef=@P58
THEN CASE
WHEN 0x08<>0x01
AND CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_011_F_000_
FROM dbo._InfoRg100966 T31
WHERE T31._Fld67386=@P59
AND T31._Fld100967RRef=T18._IDRRef
AND T31._Fld100968_TYPE=0x08
AND T31._Fld100968_RTRef=0x0001007C
AND T31._Fld100968_RRRef=ISNULL( T15._Fld116737RRef, @P60 )
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_012_F_000_
FROM dbo._InfoRg100973 T32
WHERE T32._Fld67386=@P61
AND T32._Fld100974RRef=T18._IDRRef
AND T32._Fld100975_TYPE=0x08
AND T32._Fld100975_RTRef=0x0001007C
AND T32._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END
AND 0x08<>0x01
AND CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_013_F_000_
FROM dbo._InfoRg100966 T33
WHERE T33._Fld67386=@P62
AND T33._Fld100967RRef=T18._IDRRef
AND T33._Fld100968_TYPE=0x08
AND T33._Fld100968_RTRef=0x00010103
AND T33._Fld100968_RRRef=ISNULL( T15._Fld116803RRef, @P63 )
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_014_F_000_
FROM dbo._InfoRg100973 T34
WHERE T34._Fld67386=@P64
AND T34._Fld100974RRef=T18._IDRRef
AND T34._Fld100975_TYPE=0x08
AND T34._Fld100975_RTRef=0x00010103
AND T34._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END
THEN 0x01
ELSE 0x00
END
ELSE CASE
WHEN 0x08<>0x01
AND CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_009_F_000_
FROM dbo._InfoRg100966 T35
WHERE T35._Fld67386=@P65
AND T35._Fld100967RRef=T18._IDRRef
AND T35._Fld100968_TYPE=0x08
AND T35._Fld100968_RTRef=0x0001007C
AND T35._Fld100968_RRRef=T1._Fld74288RRef
)
THEN 0x01
ELSE 0x00
END=CASE
WHEN EXISTS
(
SELECT 0x01
AS Q_010_F_000_
FROM dbo._InfoRg100973 T36
WHERE T36._Fld67386=@P66
AND T36._Fld100974RRef=T18._IDRRef
AND T36._Fld100975_TYPE=0x08
AND T36._Fld100975_RTRef=0x0001007C
AND T36._Fld100976=0x00
)
THEN 0x01
ELSE 0x00
END
THEN 0x01
ELSE 0x00
END
END=0x01
AND (0x08<>0x01
OR T1._Fld74284RRef=T22._Fld123105RRef)
)
)
ORDER BY T1._Date_Time DESC,
T1._IDRRef DESC',
N'@P1 varbinary(16),@P2 varbinary(16),@P3 varbinary(16),@P4 varbinary(16),@P5 varbinary(16),@P6 varbinary(16),@P7 varbinary(16),@P8 varbinary(16),@P9 varbinary(16),@P10 numeric(10),@P11 numeric(10),@P12 numeric(10),@P13 numeric(10),@P14 numeric(10),@P15 numeric(10),@P16 numeric(10),@P17 varbinary(16),@P18 numeric(10),@P19 numeric(10),@P20 numeric(10),@P21 numeric(10),@P22 nvarchar(4000),@P23 numeric(10),@P24 varbinary(16),@P25 numeric(10),@P26 numeric(10),@P27 numeric(10),@P28 numeric(10),@P29 numeric(10),@P30 datetime2(3),@P31 numeric(10),@P32 numeric(10),@P33 numeric(10),@P34 numeric(10),@P35 numeric(10),@P36 numeric(10),@P37 nvarchar(4000),@P38 numeric(10),@P39 varbinary(16),@P40 numeric(10),@P41 numeric(10),@P42 varbinary(16),@P43 numeric(10),@P44 numeric(10),@P45 numeric(10),@P46 numeric(10),@P47 numeric(10),@P48 varbinary(16),@P49 numeric(10),@P50 numeric(10),@P51 numeric(10),@P52 numeric(10),@P53 numeric(10),@P54 varbinary(16),@P55 varbinary(16),@P56 varbinary(16),@P57 varbinary(16),@P58 varbinary(16),@P59 numeric(10),@P60 varbinary(16),@P61 numeric(10),@P62 numeric(10),@P63 varbinary(16),@P64 numeric(10),@P65 numeric(10),@P66 numeric(10)',
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0xB96DB293C2F88D8C46DF79811923F574,
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Best Answer
I would add
OPTION(USE HINT 'DISABLE_OPTIMIZER_ROWGOAL')
to the query to disable row goals.The easiest way to spot the use of row goals is when using the
TOP()
operator, used to return 45 rows as quickly as possible in your case.The use of loop joins is more common here as it is estimating smaller result sets & using non blocking operators.
Row goals will in most cases help, but with big convoluted queries I have seen them being bothersome in the past.
By disabling these row goals you should get a more optimized plan for the entire query.
You could also disable this by adding
OPTION(QUERYTRACEON 4138)
to the end of the query.Removing the
TOP(45)
removed the row goal & improved performance in this case.Paul White has some great blog posts on row goals. Parts 1 and 2 can be found here and here. There is also Inside the Optimizer: Row Goals In Depth.
If you cannot change the query, a plan guide could be added for the specific query to disable the row goal.
Another method to remove the row goal without adding the hint(s)
Following the statement:
Again from: Setting and Identifying Row Goals in Execution Plans
You could specify a nonsensical
TOP()
with such a high number that the row goal will not be set and then wrap your actualTOP()
around it.For example:
More examples:
DB<>Fiddle
In short, the
TOP(5)
rowgoal is overriden by the much highertop(99999999999)
in the inner query, resulting in only 2 actual row goals remaining in my example, one on theTOP(99999999)
operator:And one on the Nested loops operator right after the second
TOP()
that exactly matches theEstimateRows
For a real world example with a row goal issue such as yours, I was able to change the plan shape with non-blocking operators such as NL joins due to a
TOP(5)
row goal:Actual performance issue not shown in screenshots
To hash match operators by using the
TOP(999999999)
method.This plan shape matches the query when applying the row goal disable hints.
I would still prefer to add the query hint instead of writing the two
TOP()
s. But if you are not allowed to or can't, this could help.