Optymalizacja hierarchii CTE

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Mam tabelę kont o typowej architekturze kont acct / parent do reprezentowania hierarchii kont (SQL Server 2012). Stworzyłem WIDOK za pomocą CTE, aby wyrównać hierarchię, i ogólnie działa pięknie i zgodnie z przeznaczeniem. Mogę sprawdzać hierarchię na dowolnym poziomie i łatwo przeglądać gałęzie.

Istnieje jedno pole logiki biznesowej, które należy zwrócić jako funkcję hierarchii. Pole w każdym rekordzie konta opisuje rozmiar firmy (nazwiemy to CustomerCount). Logika, którą muszę zgłosić, wymaga zsumowania CustomerCount z całego oddziału. Innymi słowy, biorąc pod uwagę konto, muszę sumować wartości liczby klientów dla tego konta wraz z każdym dzieckiem w każdym oddziale poniżej konta wzdłuż hierarchii.

Pomyślnie obliczyłem pole, używając pola hierarchii zbudowanego w CTE, które wygląda jak acct4.acct3.acct2.acct1. Problem, na który wpadam, polega po prostu na szybkim uruchomieniu. Bez tego jednego pola obliczeniowego zapytanie jest uruchamiane w ~ 3 sekund. Kiedy dodam w polu obliczeniowym, zamienia się w 4-minutowe zapytanie.

Oto najlepsza wersja, jaką udało mi się wymyślić, która zwraca poprawne wyniki. Szukam pomysłów na to, jak mogę zrestrukturyzować to JAK WIDOK bez tak dużych poświęceń dla wydajności.

Rozumiem powód, dla którego ten zwalnia (wymaga obliczenia predykatu w klauzuli where), ale nie mogę wymyślić innego sposobu, aby go ustrukturyzować i nadal uzyskiwać takie same wyniki.

Oto przykładowy kod do zbudowania tabeli i wykonania CTE w przybliżeniu dokładnie tak, jak działa w moim środowisku.

Use Tempdb
go
CREATE TABLE dbo.Account
(
   Acctid varchar(1) NOT NULL
    , Name varchar(30) NULL
    , ParentId varchar(1) NULL
    , CustomerCount int NULL
);

INSERT Account
SELECT 'A','Best Bet',NULL,21  UNION ALL
SELECT 'B','eStore','A',30 UNION ALL
SELECT 'C','Big Bens','B',75 UNION ALL
SELECT 'D','Mr. Jimbo','B',50 UNION ALL
SELECT 'E','Dr. John','C',100 UNION ALL
SELECT 'F','Brick','A',222 UNION ALL
SELECT 'G','Mortar','C',153 ;


With AccountHierarchy AS

(                                                                           --Root values have no parent
    SELECT
        Root.AcctId                                         AccountId
        , Root.Name                                         AccountName
        , Root.ParentId                                     ParentId
        , 1                                                 HierarchyLevel  
        , cast(Root.Acctid as varchar(4000))                IdHierarchy     --highest parent reads right to left as in id3.Acctid2.Acctid1
        , cast(replace(Root.Name,'.','') as varchar(4000))  NameHierarchy   --highest parent reads right to left as in name3.name2.name1 (replace '.' so name parse is easy in last step)
        , cast(Root.Acctid as varchar(4000))                HierarchySort   --reverse of above, read left to right name1.name2.name3 for sorting on reporting only
        , cast(Root.Name as varchar(4000))                  HierarchyLabel  --use for labels on reporting only, indents names under sorted hierarchy
        , Root.CustomerCount                                CustomerCount   

    FROM 
        tempdb.dbo.account Root

    WHERE
        Root.ParentID is null

    UNION ALL

    SELECT
        Recurse.Acctid                                      AccountId
        , Recurse.Name                                      AccountName
        , Recurse.ParentId                                  ParentId
        , Root.HierarchyLevel + 1                           HierarchyLevel  --next level in hierarchy
        , cast(cast(recurse.Acctid as varchar(40)) + '.' + Root.IdHierarchy as varchar(4000))   IdHierarchy --cast because in real system this is a uniqueidentifier type needs converting
        , cast(replace(recurse.Name,'.','') + '.' + Root.NameHierarchy as varchar(4000)) NameHierarchy  --replace '.' for parsing in last step, cast to make room for lots of sub levels down the hierarchy
        , cast(Root.AccountName + '.' + Recurse.Name as varchar(4000)) HierarchySort    
        , cast(space(root.HierarchyLevel * 4) + Recurse.Name as varchar(4000)) HierarchyLabel
        , Recurse.CustomerCount                             CustomerCount

    FROM
        tempdb.dbo.account Recurse INNER JOIN
        AccountHierarchy Root on Root.AccountId = Recurse.ParentId
)


SELECT
    hier.AccountId
    , Hier.AccountName
    , hier.ParentId
    , hier.HierarchyLevel
    , hier.IdHierarchy
    , hier.NameHierarchy
    , hier.HierarchyLabel
    , parsename(hier.IdHierarchy,1) Acct1Id
    , parsename(hier.NameHierarchy,1) Acct1Name     --This is why we stripped out '.' during recursion
    , parsename(hier.IdHierarchy,2) Acct2Id
    , parsename(hier.NameHierarchy,2) Acct2Name
    , parsename(hier.IdHierarchy,3) Acct3Id
    , parsename(hier.NameHierarchy,3) Acct3Name
    , parsename(hier.IdHierarchy,4) Acct4Id
    , parsename(hier.NameHierarchy,4) Acct4Name
    , hier.CustomerCount

    /* fantastic up to this point. Next block of code is what causes problem. 
        Logic of code is "sum of CustomerCount for this location and all branches below in this branch of hierarchy"
        In live environment, goes from taking 3 seconds to 4 minutes by adding this one calc */

    , (
        SELECT  
            sum(children.CustomerCount)
        FROM
            AccountHierarchy Children
        WHERE
            hier.IdHierarchy = right(children.IdHierarchy, (1 /*length of id field*/ * hier.HierarchyLevel) + hier.HierarchyLevel - 1 /*for periods inbetween ids*/)
            --"where this location's idhierarchy is within child idhierarchy"
            --previously tried a charindex(hier.IdHierarchy,children.IdHierarchy)>0, but that performed even worse
        ) TotalCustomerCount
FROM
    AccountHierarchy hier

ORDER BY
    hier.HierarchySort


drop table tempdb.dbo.Account

AKTUALIZACJA 11/20/2013

Niektóre z sugerowanych rozwiązań sprawiły, że moje soki płynęły, i próbowałem nowego podejścia, które jest bliskie, ale wprowadza nową / inną przeszkodę. Szczerze mówiąc, nie wiem, czy to gwarantuje oddzielny post, czy nie, ale ma to związek z rozwiązaniem tego problemu.

Uznałem, że to, co utrudnia sumę (liczbę klientów), to identyfikacja dzieci w kontekście hierarchii, która zaczyna się u góry i rozwija. Zacząłem więc od utworzenia hierarchii, która buduje się od podstaw, używając katalogu głównego zdefiniowanego przez „konta, które nie są rodzicami dla żadnego innego konta” i wykonując rekurencyjne połączenie wstecz (root.parentacctid = recurse.acctid)

W ten sposób mogłem po prostu dodać liczbę nadrzędnych klientów do elementu nadrzędnego, gdy nastąpi rekurencja. Z powodu tego, jak potrzebuję raportowania i poziomów, robię to od dołu do góry oprócz odgórnego, a następnie dołączam do nich za pomocą identyfikatora konta. Takie podejście okazuje się znacznie szybsze niż pierwotne zewnętrzne zapytanie klienta, ale napotkałem kilka przeszkód.

Po pierwsze, nieumyślnie rejestrowałem zduplikowaną liczbę klientów dla kont nadrzędnych dla wielu dzieci. Byłem podwójnym lub potrójnym liczeniem klientów dla niektórych acctid, według liczby dzieci. Moim rozwiązaniem było stworzenie kolejnego cte, który liczy, ile węzłów ma acct, i podzielenie acct.customercount podczas rekurencji, więc kiedy dodam całą gałąź, acct nie jest liczony podwójnie.

W tym momencie wyniki tej nowej wersji są nieprawidłowe, ale wiem dlaczego. Bottomup cte tworzy duplikaty. Kiedy rekurencja mija, szuka wszystkiego w katalogu głównym (dzieci podrzędne na poziomie niższym), które są potomkami konta w tabeli kont. Przy trzeciej rekurencji pobiera te same konta, które zrobił w drugiej i umieszcza je ponownie.

Pomysły na to, jak zrobić oddolne Cte, czy może napływają jakieś inne pomysły?

Use Tempdb
go


CREATE TABLE dbo.Account
(
    Acctid varchar(1) NOT NULL
    , Name varchar(30) NULL
    , ParentId varchar(1) NULL
    , CustomerCount int NULL
);

INSERT Account
SELECT 'A','Best Bet',NULL,1  UNION ALL
SELECT 'B','eStore','A',2 UNION ALL
SELECT 'C','Big Bens','B',3 UNION ALL
SELECT 'D','Mr. Jimbo','B',4 UNION ALL
SELECT 'E','Dr. John','C',5 UNION ALL
SELECT 'F','Brick','A',6 UNION ALL
SELECT 'G','Mortar','C',7 ;



With AccountHierarchy AS

(                                                                           --Root values have no parent
    SELECT
        Root.AcctId                                         AccountId
        , Root.Name                                         AccountName
        , Root.ParentId                                     ParentId
        , 1                                                 HierarchyLevel  
        , cast(Root.Acctid as varchar(4000))                IdHierarchy     --highest parent reads right to left as in id3.Acctid2.Acctid1
        , cast(replace(Root.Name,'.','') as varchar(4000))  NameHierarchy   --highest parent reads right to left as in name3.name2.name1 (replace '.' so name parse is easy in last step)
        , cast(Root.Acctid as varchar(4000))                HierarchySort   --reverse of above, read left to right name1.name2.name3 for sorting on reporting only
        , cast(Root.Acctid as varchar(4000))                HierarchyMatch 
        , cast(Root.Name as varchar(4000))                  HierarchyLabel  --use for labels on reporting only, indents names under sorted hierarchy
        , Root.CustomerCount                                CustomerCount   

    FROM 
        tempdb.dbo.account Root

    WHERE
        Root.ParentID is null

    UNION ALL

    SELECT
        Recurse.Acctid                                      AccountId
        , Recurse.Name                                      AccountName
        , Recurse.ParentId                                  ParentId
        , Root.HierarchyLevel + 1                           HierarchyLevel  --next level in hierarchy
        , cast(cast(recurse.Acctid as varchar(40)) + '.' + Root.IdHierarchy as varchar(4000))   IdHierarchy --cast because in real system this is a uniqueidentifier type needs converting
        , cast(replace(recurse.Name,'.','') + '.' + Root.NameHierarchy as varchar(4000)) NameHierarchy  --replace '.' for parsing in last step, cast to make room for lots of sub levels down the hierarchy
        , cast(Root.AccountName + '.' + Recurse.Name as varchar(4000)) HierarchySort    
        , CAST(CAST(Root.HierarchyMatch as varchar(40)) + '.' 
            + cast(recurse.Acctid as varchar(40))   as varchar(4000))   HierarchyMatch
        , cast(space(root.HierarchyLevel * 4) + Recurse.Name as varchar(4000)) HierarchyLabel
        , Recurse.CustomerCount                             CustomerCount

    FROM
        tempdb.dbo.account Recurse INNER JOIN
        AccountHierarchy Root on Root.AccountId = Recurse.ParentId
)

, Nodes as
(   --counts how many branches are below for any account that is parent to another
    select
        node.ParentId Acctid
        , cast(count(1) as float) Nodes
    from AccountHierarchy  node
    group by ParentId
)

, BottomUp as
(   --creates the hierarchy starting at accounts that are not parent to any other
    select
        Root.Acctid
        , root.ParentId
        , cast(isnull(root.customercount,0) as float) CustomerCount
    from
        tempdb.dbo.Account Root
    where
        not exists ( select 1 from tempdb.dbo.Account OtherAccts where root.Acctid = OtherAccts.ParentId)

    union all

    select
        Recurse.Acctid
        , Recurse.ParentId
        , root.CustomerCount + cast ((isnull(recurse.customercount,0) / nodes.nodes) as float) CustomerCount
        -- divide the recurse customercount by number of nodes to prevent duplicate customer count on accts that are parent to multiple children, see customercount cte next
    from
        tempdb.dbo.Account Recurse inner join 
        BottomUp Root on root.ParentId = recurse.acctid inner join
        Nodes on nodes.Acctid = recurse.Acctid
)

, CustomerCount as
(
    select
        sum(CustomerCount) TotalCustomerCount
        , hier.acctid
    from
        BottomUp hier
    group by 
        hier.Acctid
)


SELECT
    hier.AccountId
    , Hier.AccountName
    , hier.ParentId
    , hier.HierarchyLevel
    , hier.IdHierarchy
    , hier.NameHierarchy
    , hier.HierarchyLabel
    , hier.hierarchymatch
    , parsename(hier.IdHierarchy,1) Acct1Id
    , parsename(hier.NameHierarchy,1) Acct1Name     --This is why we stripped out '.' during recursion
    , parsename(hier.IdHierarchy,2) Acct2Id
    , parsename(hier.NameHierarchy,2) Acct2Name
    , parsename(hier.IdHierarchy,3) Acct3Id
    , parsename(hier.NameHierarchy,3) Acct3Name
    , parsename(hier.IdHierarchy,4) Acct4Id
    , parsename(hier.NameHierarchy,4) Acct4Name
    , hier.CustomerCount

    , customercount.TotalCustomerCount

FROM
    AccountHierarchy hier inner join
    CustomerCount on customercount.acctid = hier.accountid

ORDER BY
    hier.HierarchySort 



drop table tempdb.dbo.Account

Edycja: to druga próba

Oparty na odpowiedzi @Max Vernon, tutaj jest sposób na ominięcie użycia CTE w wewnętrznym podzapytaniu, które jest jak samodzielne dołączenie do CTE i przypuszczam, że jest to przyczyną niskiej wydajności. Wykorzystuje funkcje analityczne dostępne tylko w wersji SQL-Server 2012. Testowane w SQL-Fiddle

Tę część można pominąć w czytaniu, jest to kopia-wklej z odpowiedzi Maxa:

;With AccountHierarchy AS
(                                                                           
    SELECT
        Root.AcctId                                         AccountId
        , Root.Name                                         AccountName
        , Root.ParentId                                     ParentId
        , 1                                                 HierarchyLevel  
        , cast(Root.Acctid as varchar(4000))                IdHierarchyMatch        
        , cast(Root.Acctid as varchar(4000))                IdHierarchy
        , cast(replace(Root.Name,'.','') as varchar(4000))  NameHierarchy   
        , cast(Root.Acctid as varchar(4000))                HierarchySort
        , cast(Root.Name as varchar(4000))                  HierarchyLabel          ,
        Root.CustomerCount                                  CustomerCount   

    FROM 
        account Root

    WHERE
        Root.ParentID is null

    UNION ALL

    SELECT
        Recurse.Acctid                                      AccountId
        , Recurse.Name                                      AccountName
        , Recurse.ParentId                                  ParentId
        , Root.HierarchyLevel + 1                           HierarchyLevel
        , CAST(CAST(Root.IdHierarchyMatch as varchar(40)) + '.' 
            + cast(recurse.Acctid as varchar(40))   as varchar(4000))   IdHierarchyMatch
        , cast(cast(recurse.Acctid as varchar(40)) + '.' 
            + Root.IdHierarchy  as varchar(4000))           IdHierarchy
        , cast(replace(recurse.Name,'.','') + '.' 
            + Root.NameHierarchy as varchar(4000))          NameHierarchy
        , cast(Root.AccountName + '.' 
            + Recurse.Name as varchar(4000))                HierarchySort   
        , cast(space(root.HierarchyLevel * 4) 
            + Recurse.Name as varchar(4000))                HierarchyLabel
        , Recurse.CustomerCount                             CustomerCount
    FROM
        account Recurse INNER JOIN
        AccountHierarchy Root on Root.AccountId = Recurse.ParentId
)

Tutaj porządkujemy wiersze CTE za pomocą IdHierarchyMatchi obliczamy numery wierszy i sumę bieżącą (od następnego wiersza do końca).

, cte1 AS 
(
SELECT
    h.AccountId
    , h.AccountName
    , h.ParentId
    , h.HierarchyLevel
    , h.IdHierarchy
    , h.NameHierarchy
    , h.HierarchyLabel
    , parsename(h.IdHierarchy,1) Acct1Id
    , parsename(h.NameHierarchy,1) Acct1Name
    , parsename(h.IdHierarchy,2) Acct2Id
    , parsename(h.NameHierarchy,2) Acct2Name
    , parsename(h.IdHierarchy,3) Acct3Id
    , parsename(h.NameHierarchy,3) Acct3Name
    , parsename(h.IdHierarchy,4) Acct4Id
    , parsename(h.NameHierarchy,4) Acct4Name
    , h.CustomerCount
    , h.HierarchySort
    , h.IdHierarchyMatch
        , Rn = ROW_NUMBER() OVER 
                  (ORDER BY h.IdHierarchyMatch)
        , RunningCustomerCount = COALESCE(
            SUM(h.CustomerCount)
            OVER
              (ORDER BY h.IdHierarchyMatch
               ROWS BETWEEN 1 FOLLOWING
                        AND UNBOUNDED FOLLOWING)
          , 0) 
FROM
    AccountHierarchy AS h  
)

Następnie mamy jeszcze jeden pośredni CTE, w którym wykorzystujemy poprzednie sumy bieżące i numery wierszy - w zasadzie, aby znaleźć miejsce, w którym kończą się gałęzie struktury drzewa:

, cte2 AS
(
SELECT
    cte1.*
    , rn3  = LAST_VALUE(Rn) OVER 
               (PARTITION BY Acct1Id, Acct2Id, Acct3Id 
                ORDER BY Acct4Id
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)       
    , rn2  = LAST_VALUE(Rn) OVER 
               (PARTITION BY Acct1Id, Acct2Id 
                ORDER BY Acct3Id, Acct4Id
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
    , rn1  = LAST_VALUE(Rn) OVER 
               (PARTITION BY Acct1Id 
                ORDER BY Acct2Id, Acct3Id, Acct4Id
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
    , rcc3 = LAST_VALUE(RunningCustomerCount) OVER 
               (PARTITION BY Acct1Id, Acct2Id, Acct3Id 
                ORDER BY Acct4Id
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)       
    , rcc2 = LAST_VALUE(RunningCustomerCount) OVER 
               (PARTITION BY Acct1Id, Acct2Id 
                ORDER BY Acct3Id, Acct4Id
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
    , rcc1 = LAST_VALUE(RunningCustomerCount) OVER 
               (PARTITION BY Acct1Id 
                ORDER BY Acct2Id, Acct3Id, Acct4Id
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
FROM
    cte1 
) 

i na koniec budujemy ostatnią część:

SELECT
    hier.AccountId
    , hier.AccountName
    ---                        -- columns skipped 
    , hier.CustomerCount

    , TotalCustomerCount = hier.CustomerCount
        + hier.RunningCustomerCount 
        - ca.LastRunningCustomerCount

    , hier.HierarchySort
    , hier.IdHierarchyMatch
FROM
    cte2 hier
  OUTER APPLY
    ( SELECT  LastRunningCustomerCount, Rn
      FROM
      ( SELECT LastRunningCustomerCount
              = RunningCustomerCount, Rn
        FROM (SELECT NULL a) x  WHERE 4 <= HierarchyLevel 
      UNION ALL
        SELECT rcc3, Rn3
        FROM (SELECT NULL a) x  WHERE 3 <= HierarchyLevel 
      UNION ALL
        SELECT rcc2, Rn2 
        FROM (SELECT NULL a) x  WHERE 2 <= HierarchyLevel 
      UNION ALL
        SELECT rcc1, Rn1
        FROM (SELECT NULL a) x  WHERE 1 <= HierarchyLevel 
      ) x
      ORDER BY Rn 
      OFFSET 0 ROWS
      FETCH NEXT 1 ROWS ONLY
      ) ca
ORDER BY
    hier.HierarchySort ; 

I uproszczenie, przy użyciu tego samego cte1co powyższy kod. Test w SQL-Fiddle-2 . Pamiętaj, że oba rozwiązania działają przy założeniu, że masz maksymalnie cztery poziomy w swoim drzewie:

SELECT
    hier.AccountId
    ---                      -- skipping rows
    , hier.CustomerCount

    , TotalCustomerCount = CustomerCount
        + RunningCustomerCount 
        - CASE HierarchyLevel
            WHEN 4 THEN RunningCustomerCount
            WHEN 3 THEN LAST_VALUE(RunningCustomerCount) OVER 
                   (PARTITION BY Acct1Id, Acct2Id, Acct3Id 
                    ORDER BY Acct4Id
                    ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)       
            WHEN 2 THEN LAST_VALUE(RunningCustomerCount) OVER 
                   (PARTITION BY Acct1Id, Acct2Id 
                    ORDER BY Acct3Id, Acct4Id
                    ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
            WHEN 1 THEN LAST_VALUE(RunningCustomerCount) OVER 
                   (PARTITION BY Acct1Id 
                    ORDER BY Acct2Id, Acct3Id, Acct4Id
                    ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) 
          END

    , hier.HierarchySort
    , hier.IdHierarchyMatch
FROM cte1 AS hier
ORDER BY
    hier.HierarchySort ; 

Trzecie podejście, z tylko jednym CTE, dla części rekurencyjnej, a następnie tylko funkcji agregujących okna ( SUM() OVER (...)), więc powinno działać w dowolnej wersji od 2005 roku w górę. Test w SQL-Fiddle-3 To rozwiązanie zakłada, podobnie jak poprzednie, że w drzewie hierarchii są maksymalnie 4 poziomy:

;WITH AccountHierarchy AS
(                                                                           
    SELECT
          AccountId      = Root.AcctId                                         
        , AccountName    = Root.Name                                         
        , ParentId       = Root.ParentId                                     
        , HierarchyLevel = 1                                                   
        , HierarchySort  = CAST(Root.Acctid AS VARCHAR(4000))                
        , HierarchyLabel = CAST(Root.Name AS VARCHAR(4000))                   
        , Acct1Id        = CAST(Root.Acctid AS VARCHAR(4000))                
        , Acct2Id        = CAST(NULL AS VARCHAR(4000))                       
        , Acct3Id        = CAST(NULL AS VARCHAR(4000))                       
        , Acct4Id        = CAST(NULL AS VARCHAR(4000))                       
        , Acct1Name      = CAST(Root.Name AS VARCHAR(4000))                  
        , Acct2Name      = CAST(NULL AS VARCHAR(4000))                       
        , Acct3Name      = CAST(NULL AS VARCHAR(4000))                       
        , Acct4Name      = CAST(NULL AS VARCHAR(4000))                       
        , CustomerCount  = Root.CustomerCount                                   

    FROM 
        account AS Root

    WHERE
        Root.ParentID IS NULL

    UNION ALL

    SELECT
          Recurse.Acctid 
        , Recurse.Name 
        , Recurse.ParentId 
        , Root.HierarchyLevel + 1 
        , CAST(Root.AccountName + '.' 
            + Recurse.Name AS VARCHAR(4000)) 
        , CAST(SPACE(Root.HierarchyLevel * 4) 
            + Recurse.Name AS VARCHAR(4000)) 
        , Root.Acct1Id 
        , CASE WHEN Root.HierarchyLevel = 1 
              THEN cast(Recurse.Acctid AS VARCHAR(4000)) 
              ELSE Root.Acct2Id 
          END 
        , CASE WHEN Root.HierarchyLevel = 2 
              THEN CAST(Recurse.Acctid AS VARCHAR(4000)) 
              ELSE Root.Acct3Id 
          END 
        , CASE WHEN Root.HierarchyLevel = 3 
              THEN CAST(Recurse.Acctid AS VARCHAR(4000)) 
              ELSE Root.Acct4Id 
          END 

        , cast(Root.AccountName as varchar(4000))          
        , CASE WHEN Root.HierarchyLevel = 1 
              THEN CAST(Recurse.Name AS VARCHAR(4000)) 
              ELSE Root.Acct2Name 
          END 
        , CASE WHEN Root.HierarchyLevel = 2 
              THEN CAST(Recurse.Name AS VARCHAR(4000)) 
              ELSE Root.Acct3Name 
          END 
        , CASE WHEN Root.HierarchyLevel = 3 
              THEN CAST(Recurse.Name AS VARCHAR(4000)) 
              ELSE Root.Acct4Name 
          END 
        , Recurse.CustomerCount 
    FROM 
        account AS Recurse INNER JOIN 
        AccountHierarchy AS Root ON Root.AccountId = Recurse.ParentId
)

SELECT
      h.AccountId
    , h.AccountName
    , h.ParentId
    , h.HierarchyLevel
    , IdHierarchy = 
          CAST(COALESCE(h.Acct4Id+'.','') 
               + COALESCE(h.Acct3Id+'.','') 
               + COALESCE(h.Acct2Id+'.','') 
               + h.Acct1Id AS VARCHAR(4000))
    , NameHierarchy = 
          CAST(COALESCE(h.Acct4Name+'.','') 
               + COALESCE(h.Acct3Name+'.','') 
               + COALESCE(h.Acct2Name+'.','') 
               + h.Acct1Name AS VARCHAR(4000))   
    , h.HierarchyLabel
    , h.Acct1Id
    , h.Acct1Name
    , h.Acct2Id
    , h.Acct2Name
    , h.Acct3Id
    , h.Acct3Name
    , h.Acct4Id
    , h.Acct4Name
    , h.CustomerCount
    , TotalCustomerCount =  
          CASE h.HierarchyLevel
            WHEN 4 THEN h.CustomerCount
            WHEN 3 THEN SUM(h.CustomerCount) OVER 
                   (PARTITION BY h.Acct1Id, h.Acct2Id, h.Acct3Id)       
            WHEN 2 THEN SUM(h.CustomerCount) OVER 
                   (PARTITION BY Acct1Id, h.Acct2Id) 
            WHEN 1 THEN SUM(h.CustomerCount) OVER 
                   (PARTITION BY h.Acct1Id) 
          END
    , h.HierarchySort
    , IdHierarchyMatch = 
          CAST(h.Acct1Id 
               + COALESCE('.'+h.Acct2Id,'') 
               + COALESCE('.'+h.Acct3Id,'') 
               + COALESCE('.'+h.Acct4Id,'') AS VARCHAR(4000))   
FROM
    AccountHierarchy AS h  
ORDER BY
    h.HierarchySort ; 

Czwarte podejście, które oblicza jako pośrednie CTE, tabelę zamknięcia hierarchii. Test w SQL-Fiddle-4 . Korzyścią jest to, że w obliczeniach sum nie ma ograniczenia liczby poziomów.

;WITH AccountHierarchy AS
( 
    -- skipping several line, identical to the 3rd approach above
)

, ClosureTable AS
( 
    SELECT
          AccountId      = Root.AcctId  
        , AncestorId     = Root.AcctId  
        , CustomerCount  = Root.CustomerCount 
    FROM 
        account AS Root

    UNION ALL

    SELECT
          Recurse.Acctid 
        , Root.AncestorId 
        , Recurse.CustomerCount
    FROM 
        account AS Recurse INNER JOIN 
        ClosureTable AS Root ON Root.AccountId = Recurse.ParentId
)

, ClosureGroup AS
(                                                                           
    SELECT
          AccountId           = AncestorId  
        , TotalCustomerCount  = SUM(CustomerCount)                             
    FROM 
        ClosureTable AS a
    GROUP BY
        AncestorId
)

SELECT
      h.AccountId
    , h.AccountName
    , h.ParentId
    , h.HierarchyLevel 
    , h.HierarchyLabel
    , h.CustomerCount
    , cg.TotalCustomerCount 

    , h.HierarchySort
FROM
    AccountHierarchy AS h  
  JOIN
    ClosureGroup AS cg
      ON cg.AccountId = h.AccountId
ORDER BY
    h.HierarchySort ;  

Uważam, że powinno to przyspieszyć:

;With AccountHierarchy AS
(                                                                           
    SELECT
        Root.AcctId                                         AccountId
        , Root.Name                                         AccountName
        , Root.ParentId                                     ParentId
        , 1                                                 HierarchyLevel  
        , cast(Root.Acctid as varchar(4000))                IdHierarchyMatch        
        , cast(Root.Acctid as varchar(4000))                IdHierarchy
        , cast(replace(Root.Name,'.','') as varchar(4000))  NameHierarchy   
        , cast(Root.Acctid as varchar(4000))                HierarchySort
        , cast(Root.Name as varchar(4000))                  HierarchyLabel          ,
        Root.CustomerCount                                  CustomerCount   

    FROM 
        tempdb.dbo.account Root

    WHERE
        Root.ParentID is null

    UNION ALL

    SELECT
        Recurse.Acctid                                      AccountId
        , Recurse.Name                                      AccountName
        , Recurse.ParentId                                  ParentId
        , Root.HierarchyLevel + 1                           HierarchyLevel
        , CAST(CAST(Root.IdHierarchyMatch as varchar(40)) + '.' 
            + cast(recurse.Acctid as varchar(40))   as varchar(4000))   IdHierarchyMatch
        , cast(cast(recurse.Acctid as varchar(40)) + '.' 
            + Root.IdHierarchy  as varchar(4000))           IdHierarchy
        , cast(replace(recurse.Name,'.','') + '.' 
            + Root.NameHierarchy as varchar(4000))          NameHierarchy
        , cast(Root.AccountName + '.' 
            + Recurse.Name as varchar(4000))                HierarchySort   
        , cast(space(root.HierarchyLevel * 4) 
            + Recurse.Name as varchar(4000))                HierarchyLabel
        , Recurse.CustomerCount                             CustomerCount
    FROM
        tempdb.dbo.account Recurse INNER JOIN
        AccountHierarchy Root on Root.AccountId = Recurse.ParentId
)


SELECT
    hier.AccountId
    , Hier.AccountName
    , hier.ParentId
    , hier.HierarchyLevel
    , hier.IdHierarchy
    , hier.NameHierarchy
    , hier.HierarchyLabel
    , parsename(hier.IdHierarchy,1) Acct1Id
    , parsename(hier.NameHierarchy,1) Acct1Name
    , parsename(hier.IdHierarchy,2) Acct2Id
    , parsename(hier.NameHierarchy,2) Acct2Name
    , parsename(hier.IdHierarchy,3) Acct3Id
    , parsename(hier.NameHierarchy,3) Acct3Name
    , parsename(hier.IdHierarchy,4) Acct4Id
    , parsename(hier.NameHierarchy,4) Acct4Name
    , hier.CustomerCount
    , (
        SELECT  
            sum(children.CustomerCount)
        FROM
            AccountHierarchy Children
        WHERE
            Children.IdHierarchyMatch LIKE hier.IdHierarchyMatch + '%'
        ) TotalCustomerCount
        , HierarchySort
        , IdHierarchyMatch
FROM
    AccountHierarchy hier
ORDER BY
    hier.HierarchySort

Dodałem kolumnę w nazwie CTE, IdHierarchyMatchktóra jest wersją IdHierarchydo przodu, aby umożliwić klauzulę TotalCustomerCountpodzapytania WHERE.

Porównując szacunkowe koszty poddrzewa dla planów wykonania, ten sposób powinien być około 5 razy szybszy.

Dałem też szansę. Nie jest bardzo ładny, ale wydaje się, że działa lepiej.

USE Tempdb
go

SET STATISTICS IO ON;
SET STATISTICS TIME OFF;
SET NOCOUNT ON;

--------
-- assuming the original table looks something like this 
-- and you cannot control it's indexes 
-- (only widened the data types a bit for the extra sample rows)
--------
CREATE TABLE dbo.Account
    (
      Acctid VARCHAR(10) NOT NULL ,
      Name VARCHAR(100) NULL ,
      ParentId VARCHAR(10) NULL ,
      CustomerCount INT NULL
    );

--------
-- inserting the same records as in your sample
--------
INSERT  Account
        SELECT  'A' ,
                'Best Bet' ,
                NULL ,
                21
        UNION ALL
        SELECT  'B' ,
                'eStore' ,
                'A' ,
                30
        UNION ALL
        SELECT  'C' ,
                'Big Bens' ,
                'B' ,
                75
        UNION ALL
        SELECT  'D' ,
                'Mr. Jimbo' ,
                'B' ,
                50
        UNION ALL
        SELECT  'E' ,
                'Dr. John' ,
                'C' ,
                100
        UNION ALL
        SELECT  'F' ,
                'Brick' ,
                'A' ,
                222
        UNION ALL
        SELECT  'G' ,
                'Mortar' ,
                'C' ,
                153;

--------
-- now lets up the ante a bit and add some extra rows with random parents 
-- to these 7 items, it is hard to measure differences with so few rows
--------
DECLARE @numberOfRows INT = 25000
DECLARE @from INT = 1
DECLARE @to INT = 7
DECLARE @T1 TABLE ( n INT ); 

WITH    cte ( n )
          AS ( SELECT   ROW_NUMBER() OVER ( ORDER BY CURRENT_TIMESTAMP )
               FROM     sys.messages
             )
    INSERT  INTO @T1
            SELECT  n
            FROM    cte
            WHERE   n <= @numberOfRows;

INSERT  INTO dbo.Account
        ( acctId ,
          name ,
          parentId ,
          Customercount
        )
        SELECT  CHAR(64 + RandomNumber) + CAST(n AS VARCHAR(10)) AS Id ,
                CAST('item ' + CHAR(64 + RandomNumber) + CAST(n AS VARCHAR(10)) AS VARCHAR(100)) ,
                CHAR(64 + RandomNumber) AS parentId ,
                ABS(CHECKSUM(NEWID()) % 100) + 1 AS RandomCustCount
        FROM    ( SELECT    n ,
                            ABS(CHECKSUM(NEWID()) % @to) + @from AS RandomNumber
                  FROM      @T1
                ) A;

--------
-- Assuming you cannot control it's indexes, in my tests we're better off taking the IO hit of copying the data
-- to some structure that is better optimized for this query. Not quite what I initially expected,  but we seem 
-- to be better off that way.
--------
CREATE TABLE tempdb.dbo.T1
    (
      AccountId VARCHAR(10) NOT NULL
                            PRIMARY KEY NONCLUSTERED ,
      AccountName VARCHAR(100) NOT NULL ,
      ParentId VARCHAR(10) NULL ,
      HierarchyLevel INT NULL ,
      HPath VARCHAR(1000) NULL ,
      IdHierarchy VARCHAR(1000) NULL ,
      NameHierarchy VARCHAR(1000) NULL ,
      HierarchyLabel VARCHAR(1000) NULL ,
      HierarchySort VARCHAR(1000) NULL ,
      CustomerCount INT NOT NULL
    );

CREATE CLUSTERED INDEX IX_Q1
ON tempdb.dbo.T1  ([ParentId]);

-- for summing customer counts over parents
CREATE NONCLUSTERED INDEX IX_Q2 
ON tempdb.dbo.T1  (HPath) INCLUDE(CustomerCount);

INSERT  INTO tempdb.dbo.T1
        ( AccountId ,
          AccountName ,
          ParentId ,
          HierarchyLevel ,
          HPath ,
          IdHierarchy ,
          NameHierarchy ,
          HierarchyLabel ,
          HierarchySort ,
          CustomerCount 
        )
        SELECT  Acctid AS AccountId ,
                Name AS AccountName ,
                ParentId AS ParentId ,
                NULL AS HierarchyLevel ,
                NULL AS HPath ,
                NULL AS IdHierarchy ,
                NULL AS NameHierarchy ,
                NULL AS HierarchyLabel ,
                NULL AS HierarchySort ,
                CustomerCount AS CustomerCount
        FROM    tempdb.dbo.account;



--------
-- I cannot seem to force an efficient way to do the sum while selecting over the recursive cte, 
-- so I took it aside. I am sure there is a more elegant way but I can't seem to make it happen. 
-- At least it performs better this way. But it remains a very expensive query.
--------
;
WITH    AccountHierarchy
          AS ( SELECT   Root.AccountId AS AcId ,
                        Root.ParentId ,
                        1 AS HLvl ,
                        CAST(Root.AccountId AS VARCHAR(1000)) AS [HPa] ,
                        CAST(Root.accountId AS VARCHAR(1000)) AS hid ,
                        CAST(REPLACE(Root.AccountName, '.', '') AS VARCHAR(1000)) AS hn ,
                        CAST(Root.accountid AS VARCHAR(1000)) AS hs ,
                        CAST(Root.accountname AS VARCHAR(1000)) AS hl
               FROM     tempdb.dbo.T1 Root
               WHERE    Root.ParentID IS NULL
               UNION ALL
               SELECT   Recurse.AccountId AS acid ,
                        Recurse.ParentId ParentId ,
                        Root.Hlvl + 1 AS hlvl ,
                        CAST(Root.HPa + '.' + Recurse.AccountId AS VARCHAR(1000)) AS hpa ,
                        CAST(recurse.AccountId + '.' + Root.hid AS VARCHAR(1000)) AS hid ,
                        CAST(REPLACE(recurse.AccountName, '.', '') + '.' + Root.hn AS VARCHAR(1000)) AS hn ,
                        CAST(Root.hs + '.' + Recurse.AccountName AS VARCHAR(1000)) AS hs ,
                        CAST(SPACE(root.hlvl * 4) + Recurse.AccountName AS VARCHAR(1000)) AS hl
               FROM     tempdb.dbo.T1 Recurse
                        INNER JOIN AccountHierarchy Root ON Root.AcId = Recurse.ParentId
             )
    UPDATE  tempdb.dbo.T1
    SET     HierarchyLevel = HLvl ,
            HPath = Hpa ,
            IdHierarchy = hid ,
            NameHierarchy = hn ,
            HierarchyLabel = hl ,
            HierarchySort = hs
    FROM    AccountHierarchy
    WHERE   AccountId = AcId;

SELECT  --HPath ,
        AccountId ,
        AccountName ,
        ParentId ,
        HierarchyLevel ,
        IdHierarchy ,
        NameHierarchy ,
        HierarchyLabel ,
        PARSENAME(IdHierarchy, 1) Acct1Id ,
        PARSENAME(NameHierarchy, 1) Acct1Name ,
        PARSENAME(IdHierarchy, 2) Acct2Id ,
        PARSENAME(NameHierarchy, 2) Acct2Name ,
        PARSENAME(IdHierarchy, 3) Acct3Id ,
        PARSENAME(NameHierarchy, 3) Acct3Name ,
        PARSENAME(IdHierarchy, 4) Acct4Id ,
        PARSENAME(NameHierarchy, 4) Acct4Name ,
        CustomerCount ,
        Cnt.TotalCustomerCount
FROM    tempdb.dbo.t1 Hier
        CROSS APPLY ( SELECT    SUM(CustomerCount) AS TotalCustomerCount
                      FROM      tempdb.dbo.t1
                      WHERE     HPath LIKE hier.HPath + '%'
                    ) Cnt
ORDER BY HierarchySort;

DROP TABLE tempdb.dbo.t1;
DROP TABLE tempdb.dbo.Account;