Feeling pain in importing data to index table; here it is dub way out

Disable Index and Insert!!! Is this the solution???

In order to speed the import of our large amount of data we want to disable all non-clustered indexes.  The easiest way of doing this is to disable the clustered index since whenever we disable a clustered index; it disables all the non-clustered indexes on the table as well. 

NOTE: An interesting side-effect that saves us the time of disabling each non-clustered index individually but presents us with a serious problem: once a clustered index is disabled, users can not access the underlying table data.

Let me say that again: once a clustered index is disabled, users can not access the underlying table data. 

So, we want the ease of disabling all indexes at once but need to mitigate the rather pesky side-effect of losing access to the data that occurs when one disables a clustered index.  The way to do that is to disable the clustered index, then re-enable it, leaving the non-clustered indexes disabled.

Lets fuel up our discussion by stimulate the same scenario, we are create table  InsertNdisableIndexDemo and defining cluster index on primary key and non cluster index on fName, sName and education

create table InsertNdisableIndexDemo

(id int identity(1,1) primary key clustered,

fName varchar(10),

sName varchar(10),

age int,

education varchar(10))

command(s) completed successfully.

create nonclustered index nonClusterd_fName ON InsertNdisableIndexDemo (fName)

create nonclustered index nonClusterd_sName ON InsertNdisableIndexDemo (sName)

create nonclustered index nonClusterd_education ON InsertNdisableIndexDemo (education)

Command(s) completed successfully.

Now we have indexes on place for InsertNdisableIndexDemo table, lets query the sys.indexs table to see all the indexes and the status of each index.

select name 'IndexName', type_desc, is_disabled from sys.indexes

where object_id = (select object_id from sys.objects where name = 'InsertNdisableIndexDemo')

IndexName                       type_desc     is_disabled

------------------------------- ---------     -----------

PK__InsertNd__3213E83F403A8C7D  CLUSTERED     0

nonClusterd_fName               NONCLUSTERED  0

nonClusterd_sName               NONCLUSTERED  0

nonClusterd_education           NONCLUSTERED  0

(4 row(s) affected)

We can see from the result of query that all indexes are in place and are in enable status. Now our task is to diable the indexes so as to ease the work of importing data to sql server, for this we will be taking the below approach, let find out each step

Follow this procedure:

1. Disable all indexes on a table by disabling the clustered index
2. Rebuild only the clustered index (since a rebuild is the method for re-enabling an index), leaving the non-clustered indexes disabled
3. Check disabled indexes
4. Check to make sure no clustered indexes are disabled in the database
5. Import the data
6. Rebuild all indexes (since a rebuild is the method for re-enabling an index) on a table

Disable all indexes on a table by disabling the clustered index

We are now disabling our cluster index, which will ultimately all non cluster index will get disable.

  

alter index PK__InsertNd__3213E83F403A8C7D on InsertNdisableIndexDemo disable

Warning: Index 'nonClusterd_fName' on table 'InsertNdisableIndexDemo' was disabled as a result of disabling the clustered index on the table.

Warning: Index 'nonClusterd_sName' on table 'InsertNdisableIndexDemo' was disabled as a result of disabling the clustered index on the table.

Warning: Index 'nonClusterd_education' on table 'InsertNdisableIndexDemo' was disabled as a result of disabling the clustered index on the table.

We can check out the indexes status by querying the sys.indexes table

select name 'IndexName', type_desc, is_disabled from sys.indexes

where object_id = (select object_id from sys.objects where name = 'InsertNdisableIndexDemo')

IndexName                       type_desc     is_disabled

------------------------------- ---------     -----------

PK__InsertNd__3213E83F403A8C7D  CLUSTERED     1

nonClusterd_fName               NONCLUSTERED  1

nonClusterd_sName               NONCLUSTERED  1

nonClusterd_education           NONCLUSTERED  1

(4 row(s) affected)

As to our discussion all the non cluster indexes are disabled by disabling the cluster index.  

Now if we try to insert data to the table, it will give error

insert into InsertNdisableIndexDemo

select 'Akansha','Patnaik',24,'BE'

Msg 8655, Level 16, State 1, Line 1

The query processor is unable to produce a plan because the index 'PK__InsertNd__3213E83F403A8C7D' on table or view 'InsertNdisableIndexDemo' is disabled.

Reason: Cluster index is disable

Rebuild clustered index

alter index PK__InsertNd__3213E83F403A8C7D on InsertNdisableIndexDemo rebuild

Command(s) completed successfully.

This will rebuild only the clustered index, re-enabling access to the data. Now lets check the disable index

select name 'IndexName', type_desc, is_disabled from sys.indexes

where object_id = (select object_id from sys.objects where name = 'InsertNdisableIndexDemo')

IndexName                       type_desc     is_disabled

------------------------------- ---------     -----------

PK__InsertNd__3213E83F403A8C7D  CLUSTERED     0

nonClusterd_fName               NONCLUSTERED  1

nonClusterd_sName               NONCLUSTERED  1

nonClusterd_education           NONCLUSTERED  1

(4 row(s) affected)

Now, checking the disabled indexes on InsertNdisableIndexDemo shows that only the non-clustered indexes are disabled.

 Once all non cluster index gets disabled, you can go ahead and perform your import/insert of data to your table.

insert into InsertNdisableIndexDemo

select 'Akansha','Patnaik',24,'BE'

union all

select 'Pratiksha','Sharma',24,'Mtec'

union all

select 'Aadhya','Mohapatra',24,'BE'

union all

select 'Prajna','Das',24,'Btec'

union all

select 'Nandani','Ray',24,'MBA'

union all

select 'Apali','Mohanty',24,'CA'

union all

select 'Niharika','Patnaik',24,'BE'

(7 row(s) affected)

Once the insert completes we can rebuild all indexes which will both re-enable the indexes and update them with the new data.

alter index all on InsertNdisableIndexDemo rebuild

select name 'IndexName', type_desc, is_disabled from sys.indexes

where object_id = (select object_id from sys.objects where name = 'InsertNdisableIndexDemo')

IndexName                       type_desc     is_disabled

------------------------------- ---------     -----------

PK__InsertNd__3213E83F403A8C7D  CLUSTERED     0

nonClusterd_fName               NONCLUSTERED  0

nonClusterd_sName               NONCLUSTERED  0

nonClusterd_education           NONCLUSTERED  0

(4 row(s) affected)

Just code,have fun. Enjoy the game