Indexing Fields in Servicenow

[Madhan007]

Hi Everyone,

We are planning to Index the following fields.
1. Custom Corelation ID field on Security Incident [sn_si_incident] Table.

2.Employment Number field on HR Profile Table

3.Code field on Cost Center Table

4.Custom field on a Group table

5.Custom field on a core Table

Note : All these fields are being used as Coalesce fields in Transform maps

I want to learn a few things about Indexing -
1. will there be any impact if the field is Indexed ?
2.How much time does it take to index a field for a table and will there be any performance issues on the Instance while indexing a field ?

3.Will there be any impact on Transform Maps ( since these fields are being used as Coelasce)?
4.Can we move Indexing changes on Update sets ?

Please pour your Insights.

Thanks in Advance!!

[Ankur Bawiskar · Accepted solution]

@Madhan007 

my thoughts and reference links

Improve performance: database indexes and slow queries 

Fields Used To Coalesce Records In A Table Transform Map Should Be Indexed 

Area	Key Point
Query Performance	Improves lookup and import speed, especially for coalesce fields
Write Performance	Slightly slower inserts/updates due to index maintenance
Indexing Time	Typically a few minutes; longer for large/busy tables; minor latency possible during build
Impact on Transform Map	Enhances transform map performance; no functional risk; best practice to index coalesce fields
Migration	Index definitions are NOT captured in update sets; must be recreated manually in each environment
Best Practice	Test in sub-prod first; index only relevant fields to avoid unnecessary overhead

If my response helped please mark it correct and close the thread so that it benefits future readers.

[Madhan007]

@Ankur Bawiskar , Thanks for the reply.

which Indexes should I mark as Unique ?

[Ankur Bawiskar]

@Madhan007 

if you are asking which field on table to be marked as index?

then whichever field is Unique that one.

Example: on incident table it's number field

If my response helped please mark it correct and close the thread so that it benefits future readers.

[Madhan007]

@Ankur Bawiskar while creating an Index, there is an option called Unique . when should I check it ? 
Also I tried Indexing a field in PDI, one update is captured in update set, a record in v_index_creator table.

Thanks!