Discussion in 'ALL SQL SERVER QUESTIONS' started by lara999, Oct 25, 2012.
How to reduce BootStrap lookups in executino plan?
There are mainly 2 kinds of lookup :
· Bookmark lookup (key lookup )
· RID (Row identified lookup )
Each one has it its own cases, reasons, impacts and solutions as follows:
Bookmark lookup is resulted by lots of reasons :
· Missing covering compound indexes that perhaps might be some column is missed from index design either key columns part or Include column part that yields the query execution plans to scan the data entity of table to fetch values of this column , and this can impact adversely on query performance thereby you have to create efficient covering compound indexes.
· Data Type conversation resulted of Using different Data types in where conditions like you are using EmpployeeID=123455 although it should be EmpployeeID=’123455’ as ExmployeeID is already varchar column not int column, thereby you have to use data type wisely ..
RID (Record identified lookup ) is resulted of one major reason which is missing clustered indexes on the relevant tables which they are called then Heap tables thereby the main solutions here is to create a clustered index on the relevant table and it shouldn’t be PK as you can ignore the uniqueness feature of this new clustered index and that is adequate enough for performance aspect..
You can read more about index tuning at my blog : http://www.sqlserver-performance-tuning.com/apps/blog/show/12927042-t-sql-performance-optimization-6-6/
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