Need to convert a recursive CTE query to an index query

Question

After going through all the hard work of writing a recursive CTE query to satisfy my needs, I realize that I cannot use it because it does not work in an indexed view. So I need something else to replace the CTE below. (Yes, you can use CTE in an unindexed form, but it is too slow for me).

Requirements:

• My ultimate goal is to have a self-updating indexed view (it should not be a view, but something similar) ... that is, if the data changes in any of the tables, then the view needs to be updated.

• A view needs to be indexed because it must be very fast and data does not change very often. Unfortunately, non-indexed browsing using CTE takes 3-5 seconds to start, which is too long for my needs. I need a request to run in milliseconds. A recursive table contains several hundred thousand records.

As for my research, the best solution to meet all these requirements is an indexed view, but I'm open to any solution.

CTE can be found in the answer to my other post . Or here again:

DECLARE @tbl TABLE ( 
     Id INT 
    ,[Name] VARCHAR(20) 
    ,ParentId INT 
    ) 

INSERT INTO @tbl( Id, Name, ParentId ) 
VALUES 
 (1, 'Europe', NULL) 
,(2, 'Asia',   NULL) 
,(3, 'Germany', 1) 
,(4, 'UK',      1) 
,(5, 'China',   2) 
,(6, 'India',   2) 
,(7, 'Scotland', 4) 
,(8, 'Edinburgh', 7) 
,(9, 'Leith', 8) 

; 
DECLARE @tbl2 table (id int, abbreviation varchar(10), tbl_id int)
INSERT INTO @tbl2( Id, Abbreviation, tbl_id ) 
VALUES 
 (100, 'EU', 1) 
,(101, 'AS', 2) 
,(102, 'DE', 3) 
,(103, 'CN', 5)

;WITH abbr AS (
    SELECT a.*, isnull(b.abbreviation,'') abbreviation
    FROM @tbl a
    left join @tbl2 b on a.Id = b.tbl_id
), abcd AS ( 
          -- anchor 
        SELECT  id, [Name], ParentID,
                CAST(([Name]) AS VARCHAR(1000)) [Path],
                cast(abbreviation as varchar(max)) abbreviation
        FROM    abbr
        WHERE   ParentId IS NULL 
        UNION ALL
          --recursive member 
        SELECT  t.id, t.[Name], t.ParentID, 
                CAST((a.path + '/' + t.Name) AS VARCHAR(1000)) [Path],
                isnull(nullif(t.abbreviation,'')+',', '') + a.abbreviation
        FROM    abbr AS t 
                JOIN abcd AS a 
                  ON t.ParentId = a.id 
       )
SELECT *, [Path] + ':' + abbreviation
FROM abcd

Answer 1

, (self join, cte, udf accessing data ..), .

4 ( 5). CTE

CREATE FUNCTION dbo.GetHierPath(@hier_id int) returns varchar(max)
WITH SCHEMABINDING
as
begin
return (
    select FullPath =
               isnull(H5.Name+'/','') + 
               isnull(H4.Name+'/','') +
               isnull(H3.Name+'/','') +
               isnull(H2.Name+'/','') +
               H1.Name
             +
               ':'
             +
               isnull(STUFF(
               isnull(','+A1.abbreviation,'') +
               isnull(','+A2.abbreviation,'') + 
               isnull(','+A3.abbreviation,'') +
               isnull(','+A4.abbreviation,'') +
               isnull(','+A5.abbreviation,''),1,1,''),'')
    from dbo.HIER H1
    left join dbo.ABBR A1 on A1.hier_id = H1.Id
    left join dbo.HIER H2 on H1.ParentId = H2.Id
    left join dbo.ABBR A2 on A2.hier_id = H2.Id
    left join dbo.HIER H3 on H2.ParentId = H3.Id
    left join dbo.ABBR A3 on A3.hier_id = H3.Id
    left join dbo.HIER H4 on H3.ParentId = H4.Id
    left join dbo.ABBR A4 on A4.hier_id = H4.Id
    left join dbo.HIER H5 on H4.ParentId = H5.Id
    left join dbo.ABBR A5 on A5.hier_id = H5.Id
    where H1.id = @hier_id)
end
GO

, fullpath, , 2 CTE, dbo.GetHierPath ':' (left=>path, right=>abbreviations)

-- index maximum key length is 900, based on your data, 400 is enough
ALTER TABLE HIER ADD FullPath VARCHAR(400)

- X , Y Z, INSTEAD OF AFTER. ,

• , , .
• CTE 3-5 , .

, 3-5 ( , 5- ).

CREATE TRIGGER TG_HIER
ON HIER
AFTER INSERT, UPDATE, DELETE
AS
UPDATE HIER
SET FullPath = dbo.GetHierPath(HIER.Id)

,

create index ix_hier_fullpath on HIER(FullPath)

_{, .}

TSQL

.

CREATE TABLE dbo.HIER (Id INT Primary Key Clustered, [Name] VARCHAR(20) ,ParentId INT)
;
INSERT dbo.HIER( Id, Name, ParentId ) VALUES 
     (1, 'Europe', NULL) 
    ,(2, 'Asia',   NULL) 
    ,(3, 'Germany', 1) 
    ,(4, 'UK',      1) 
    ,(5, 'China',   2) 
    ,(6, 'India',   2) 
    ,(7, 'Scotland', 4) 
    ,(8, 'Edinburgh', 7) 
    ,(9, 'Leith', 8)
    ,(10, 'Antartica', NULL) 
; 
CREATE TABLE dbo.ABBR (id int primary key clustered, abbreviation varchar(10), hier_id int)
;
INSERT dbo.ABBR( Id, Abbreviation, hier_id ) VALUES 
     (100, 'EU', 1) 
    ,(101, 'AS', 2) 
    ,(102, 'DE', 3) 
    ,(103, 'CN', 5)
GO

EDIT - ,

, , , FullPath HIER.ID. support function where H1.id = @hier_id . , FullPath PathOnly Abbreviation . CTE, , .