Detect Redundant Indexes

August 26, 2004



>>Script Language and Platform: T-Sql
This script gives a table, with Table, Index, Index contained, Index that contains.

I recommend to review each case, before you drop.

I run it in the Query Analyzer, one statement at a time.

Author: Fernando Madrigal Hidalgo


USE database

-- tab,idx,col,order
create view listaidxcols as 
select SO.name as tabname,
       SI.name as idxname,
       IK.keyno as keyno,
       SC.name as colname
from sysindexkeys IK, 
     syscolumns SC,
     sysindexes SI,
     sysobjects SO
where -- Link syscolumns
      IK.id=SC.id 
and   IK.colid=SC.colid
-- link sysindexes
and   IK.id=SI.id 
and   IK.indid=SI.indid
-- Link a sysObjects (tablas)
and   IK.id=SO.id
and   SO.xtype='U'
and   SI.name   not like '_WA_Sys_%'
and   SI.name   not like 'hind_%'

--  how many cols x index
create view cantcolsidx
as select tabname, 
          idxname, 
          count(*) as numllaves
from listaidxcols
group by tabname,idxname

-- get the redundant index list
select A.tabname as tabla,A.idxname as Aidx, B.idxname as Bidx
from cantcolsidx A, cantcolsidx B
where A.tabname  = B.tabname
and A.numllaves < B.numllaves
and A.idxname   <> B.idxname
and A.numllaves in (
    select count(*)
    from listaidxcols C, listaidxcols D
    where C.tabname=A.tabname
    and   C.idxname=A.idxname
    and   D.tabname=B.tabname
    and   D.idxname=B.idxname
    and   C.idxname<>D.idxname
    and   C.colname=D.colname
    and   C.keyno  =D.keyno
)

-- Clean up
drop view listaidxcols;
drop view cantcolsidx;

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