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Trying to improve the vIew performance


Trying to improve the vIew performance

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meetvini.reddy
meetvini.reddy
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Group: General Forum Members
Points: 1 Visits: 389
I have which im looking to optimize ...

I have tried whatever i could think like Creating indexes, schema binding the view to create an index on the view ([dbo].v_adnetwork..... View in the code), included columns, but to no success. Could any one suggest anything which could help me

Below is how the view looks

select
client_name,
client_id,
web_id,
CASE
    when active_hierarchy.trending_id is null
    then 1   -- web_id expired
    else
      CASE
         when mapping_is_historical=1
         then 2
         else 0

    end
end is_historical
from
      (
         select distinct client_name,client_id,web_id,
         CASE
            when dbo.CurrentEffectiveDate(-1) between EFFECTIVE_DATE and EXPIRATION_DATE
            then 0
            else 1
         end mapping_is_historical
         from
          (   select category_id as webster_category_id,
                     trending_id as web_id,
                     map.EFFECTIVE_DATE,
                     map.EXPIRATION_DATE
               from object_category_map map (nolock),
               level l (nolock)
               where category_index between 50000 and 60000
               and
               (object_id=level_id and level_type='SYN'
                or
                object_id=level_id and level_type='CUS' and level_level=1
                or
                object_id=level_id and level_type='ALT' and right(level_name,3)<>'_AR'
               Wink
             ) entity_client_map,

             (
             select category_id as webster_category_id, CATEGORY_NAME as client_name, CATEGORY_DESCRIPTION as client_id
             from category nolock
             ) client_defintion
               where client_defintion.webster_category_id=entity_client_map.webster_category_id
               and client_defintion.webster_category_id=entity_client_map.webster_category_id
       ) all_client_web_mapping_active_and_expired

left outer join

      (
         select trending_id,
         case when hierarchy_id is null then syn.level_type
             else other_type.level_type
         end as level_type
         from level syn (nolock)
         left outer join
         (
            select dc_hierarchy_id as hierarchy_id,'WGG' as level_type
            from [dbo].v_distributed_content (nolock)
            union
            select adn_hierarchy_id as hierarchy_id,'ADN' as level_type
            from [dbo].v_adnetwork (nolock)
         Wink other_type
         on level_group_id=hierarchy_id
         where dbo.CurrentEffectiveDate(-1) between syn.EFFECTIVE_DATE and syn.EXPIRATION_DATE
      Wink active_hierarchy

on all_client_web_mapping_active_and_expired.web_id = active_hierarchy.trending_id


Thanks
Sean Lange
Sean Lange
SSCoach
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Group: General Forum Members
Points: 16542 Visits: 16997
Hi and welcome to SSC.

The first I did was run through a formatter so I could read it.




SELECT client_name
   ,client_id
   ,web_id
   ,CASE
      WHEN active_hierarchy.trending_id IS NULL
         THEN 1 -- web_id expired
      ELSE CASE
            WHEN mapping_is_historical = 1
               THEN 2
            ELSE 0
            END
      END is_historical
FROM (
   SELECT DISTINCT client_name
      ,client_id
      ,web_id
      ,CASE
         WHEN dbo.CurrentEffectiveDate(- 1) BETWEEN EFFECTIVE_DATE
               AND EXPIRATION_DATE
            THEN 0
         ELSE 1
         END mapping_is_historical
   FROM (
      SELECT category_id AS webster_category_id
         ,trending_id AS web_id
         ,map.EFFECTIVE_DATE
         ,map.EXPIRATION_DATE
      FROM object_category_map map(NOLOCK)
         ,LEVEL l(NOLOCK)
      WHERE category_index BETWEEN 50000
            AND 60000
         AND (
            object_id = level_id
            AND level_type = 'SYN'
            OR object_id = level_id
            AND level_type = 'CUS'
            AND level_level = 1
            OR object_id = level_id
            AND level_type = 'ALT'
            AND right(level_name, 3) <> '_AR'
            Wink
      Wink entity_client_map
      ,(
         SELECT category_id AS webster_category_id
            ,CATEGORY_NAME AS client_name
            ,CATEGORY_DESCRIPTION AS client_id
         FROM category NOLOCK
         Wink client_defintion
   WHERE client_defintion.webster_category_id = entity_client_map.webster_category_id
      AND client_defintion.webster_category_id = entity_client_map.webster_category_id
   Wink all_client_web_mapping_active_and_expired
LEFT JOIN (
   SELECT trending_id
      ,CASE
         WHEN hierarchy_id IS NULL
            THEN syn.level_type
         ELSE other_type.level_type
         END AS level_type
   FROM LEVEL syn(NOLOCK)
   LEFT JOIN (
      SELECT dc_hierarchy_id AS hierarchy_id
         ,'WGG' AS level_type
      FROM [dbo].v_distributed_content(NOLOCK)
      
      UNION
      
      SELECT adn_hierarchy_id AS hierarchy_id
         ,'ADN' AS level_type
      FROM [dbo].v_adnetwork(NOLOCK)
      Wink other_type ON level_group_id = hierarchy_id
   WHERE dbo.CurrentEffectiveDate(- 1) BETWEEN syn.EFFECTIVE_DATE
         AND syn.EXPIRATION_DATE
   Wink active_hierarchy ON all_client_web_mapping_active_and_expired.web_id = active_hierarchy.trending_id




A couple of things just jump off the page as performance hogs here.

First you have a scalar function CurrentEffectiveDate.

Secondly you have several different predicates that are nonSARGable. Like right(level_name, 3) <> '_AR'. No matter what kind of indexing you do there you will have a scan. That one is actually nonSARGable twice. First you have the column inside a function and then you have a <> comparison.

You have what looks like views joining views from within a subselect that do a UNION to other views joining views.

You might want to take a look at this article that explains best practices when trying to solve performance problems. http://www.sqlservercentral.com/articles/SQLServerCentral/66909/

Last but not least, be VERY careful using the NOLOCK hint, especially in a view. If duplicate data, missing data and dirty reads are ok then this hint may be ok.

http://blogs.msdn.com/b/davidlean/archive/2009/04/06/sql-server-nolock-hint-other-poor-ideas.aspx

If possible using snapshot isolation would be better.

http://msdn.microsoft.com/en-us/library/ms173763.aspx

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