How to Repair a Corrupted Mptt Tree (Nested Set) in the Database Using SQL

How to repair a corrupted MPTT tree (nested set) in the database using SQL?

Using SQL Server, following script seems to be working for me.

Output testscript

category_id name                 parent      lft         rgt         lftcalc     rgtcalc
----------- -------------------- ----------- ----------- ----------- ----------- -----------
1           ELECTRONICS          NULL        1           20          1           20
2           TELEVISIONS          1           2           9           2           9
3           TUBE                 2           3           4           3           4
4           LCD                  2           5           6           5           6
5           PLASMA               2           7           8           7           8
6           PORTABLE ELECTRONICS 1           10          19          10          19
7           MP3 PLAYERS          6           11          14          11          14
8           FLASH                7           12          13          12          13
9           CD PLAYERS           6           15          16          15          16
10          2 WAY RADIOS         6           17          18          17          18

Script

SET NOCOUNT ON
GO

DECLARE @nested_category TABLE (
 category_id INT PRIMARY KEY,
 name VARCHAR(20) NOT NULL,
 parent INT,
 lft INT,
 rgt INT
);

DECLARE @current_Category_ID INTEGER
DECLARE @current_parent INTEGER
DECLARE @SafeGuard INTEGER
DECLARE @myLeft INTEGER
SET @SafeGuard = 100

INSERT INTO @nested_category 
SELECT           1,'ELECTRONICS',NULL,NULL,NULL
UNION ALL SELECT 2,'TELEVISIONS',1,NULL,NULL
UNION ALL SELECT 3,'TUBE',2,NULL,NULL
UNION ALL SELECT 4,'LCD',2,NULL,NULL
UNION ALL SELECT 5,'PLASMA',2,NULL,NULL
UNION ALL SELECT 6,'PORTABLE ELECTRONICS',1,NULL,NULL
UNION ALL SELECT 7,'MP3 PLAYERS',6,NULL,NULL
UNION ALL SELECT 8,'FLASH',7,NULL,NULL
UNION ALL SELECT 9,'CD PLAYERS',6,NULL,NULL
UNION ALL SELECT 10,'2 WAY RADIOS',6,NULL,NULL

/* Initialize */
UPDATE  @nested_category 
SET     lft = 1
        , rgt = 2
WHERE   parent IS NULL

UPDATE  @nested_category 
SET     lft = NULL
        , rgt = NULL
WHERE   parent IS NOT NULL

WHILE EXISTS (SELECT * FROM @nested_category WHERE lft IS NULL) AND @SafeGuard > 0
BEGIN
  SELECT  @current_Category_ID = MAX(nc.category_id)
  FROM    @nested_category nc
          INNER JOIN @nested_category nc2 ON nc2.category_id = nc.parent
  WHERE   nc.lft IS NULL
          AND nc2.lft IS NOT NULL

  SELECT  @current_parent = parent
  FROM    @nested_category
  WHERE   category_id = @current_category_id

  SELECT  @myLeft = lft
  FROM    @nested_category
  WHERE   category_id = @current_parent

  UPDATE @nested_category SET rgt = rgt + 2 WHERE rgt > @myLeft;
  UPDATE @nested_category SET lft = lft + 2 WHERE lft > @myLeft;
  UPDATE @nested_category SET lft = @myLeft + 1, rgt = @myLeft + 2 WHERE category_id = @current_category_id

  SET @SafeGuard = @SafeGuard - 1
END

SELECT * FROM @nested_category ORDER BY category_id

SELECT  COUNT(node.name), node.name, MIN(node.lft)
FROM    @nested_category AS node,
        @nested_category AS parent
WHERE   node.lft BETWEEN parent.lft AND parent.rgt
GROUP BY 
        node.name
ORDER BY
        3, 1

Testscript ##

SET NOCOUNT ON
GO

DECLARE @nested_category TABLE (
 category_id INT PRIMARY KEY,
 name VARCHAR(20) NOT NULL,
 parent INT,
 lft INT,
 rgt INT, 
 lftcalc INT,
 rgtcalc INT
);

INSERT INTO @nested_category 
SELECT           1,'ELECTRONICS',NULL,1,20,NULL,NULL
UNION ALL SELECT 2,'TELEVISIONS',1,2,9,NULL,NULL
UNION ALL SELECT 3,'TUBE',2,3,4,NULL,NULL
UNION ALL SELECT 4,'LCD',2,5,6,NULL,NULL
UNION ALL SELECT 5,'PLASMA',2,7,8,NULL,NULL
UNION ALL SELECT 6,'PORTABLE ELECTRONICS',1,10,19,NULL,NULL
UNION ALL SELECT 7,'MP3 PLAYERS',6,11,14,NULL,NULL
UNION ALL SELECT 8,'FLASH',7,12,13,NULL,NULL
UNION ALL SELECT 9,'CD PLAYERS',6,15,16,NULL,NULL
UNION ALL SELECT 10,'2 WAY RADIOS',6,17,18,NULL,NULL

/* Initialize */
UPDATE  @nested_category 
SET     lftcalc = 1
        , rgtcalc = 2
WHERE   parent IS NULL

DECLARE @current_Category_ID INTEGER
DECLARE @current_parent INTEGER
DECLARE @SafeGuard INTEGER
DECLARE @myRight INTEGER
DECLARE @myLeft INTEGER
SET @SafeGuard = 100
WHILE EXISTS (SELECT * FROM @nested_category WHERE lftcalc IS NULL) AND @SafeGuard > 0
BEGIN
  SELECT  @current_Category_ID = MAX(nc.category_id)
  FROM    @nested_category nc
          INNER JOIN @nested_category nc2 ON nc2.category_id = nc.parent
  WHERE   nc.lftcalc IS NULL
          AND nc2.lftcalc IS NOT NULL

  SELECT  @current_parent = parent
  FROM    @nested_category
  WHERE   category_id = @current_category_id

  SELECT  @myLeft = lftcalc
  FROM    @nested_category
  WHERE   category_id = @current_parent

  UPDATE @nested_category SET rgtcalc = rgtcalc + 2 WHERE rgtcalc > @myLeft;
  UPDATE @nested_category SET lftcalc = lftcalc + 2 WHERE lftcalc > @myLeft;
  UPDATE @nested_category SET lftcalc = @myLeft + 1, rgtcalc = @myLeft + 2 WHERE category_id = @current_category_id

  SELECT * FROM @nested_category WHERE category_id = @current_parent
  SELECT * FROM @nested_category ORDER BY category_id
  SET @SafeGuard = @SafeGuard - 1
END

SELECT * FROM @nested_category ORDER BY category_id

SELECT  COUNT(node.name), node.name, MIN(node.lft)
FROM    @nested_category AS node,
        @nested_category AS parent
WHERE   node.lft BETWEEN parent.lft AND parent.rgt
GROUP BY 
        node.name
ORDER BY
        3, 1

How to optimize a 'col = col + 1' UPDATE query that runs on 100,000+ records?

I never used it, but if your have enough memory, try the memory table.

Create a table with the same structure as tree, insert into .. select from .., run your scripts against the memory table, and write it back.

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