I read a lot of articles about list threshold and indexes. for example some of the weird things i read, is that if we have a list/library which already exceed the threshold (5,000), and we tried to add indexes to it (to have our lists views working again), then sharepoint will not allow us to index a list which already exceed the threshold. So currently I have these cases., which i am not sure about:-
- Inside SharePoint online, I have 2 document libraries each one contain around 300++ documents and folders/sub-folders.
- Inside sharepoint online, i have a cusotm list which contain 500++ items.
- Inside sharepoint on-premises 2013 i have a document library which contain 2,500++ documents and folders.
- Inside sharepoint on-premises 2013 i have a custom list which contain 3,000++ items.
now inside the above cases i did not create any indexes, and now i am revisiting these lists/libraries to add indexes. but my question is; if we can add indexes to the lists/libraries which already contain items and documents (of course technically i can do so, from the list setting >> Add indexes)? or the indexes need to be added to empty lists/libraries for them to work correctly? or since the lists/libraries did not exceed the threshold limit yet, then it is fine to add indexes to them while they have items/documents inside them?
Second question, how i can confirm that our lists/libraries are being indexed correctly? as i read some articles which mentioned that users have defined indexes on their lists/libraries when they created them, and this did not prevent them from receiving threshold errors when their lists/libraries exceed the threshold limit, and when they open a ticket with Microsoft, Microsoft replied that they can not support indexes on the lists, in other words the indexes were corrupted. so how i can monitor/check if the indexes on our lists/libraries are valid?