I am having a SharePoint list which contains millions of ite

Hi,

 

When there are more than 5000 items in sharepoint list that yiu have to query you are obviously stuck with the thresh hold limitation  . This is a restriction imposed in Share Point by design  . Though you can change it in Central Admin dont change it as it will cause Performance issues . You are basically left with 2 options.

 

1. Create a new view in the big list with a filter that will show a subset of the main data. Then query against this view in CSOM/JSOM or server side

 

2. Create an index on the field that comes in your CAML Query . Indexing helps to circumvent the thresh hold issue 

 

Ref :https://thedotnetter.wordpress.com/2013/04/25/spquery-and-the-list-view-threshold/