I've got a large list (>75,000 items, 41 columns) and therefore have to follow all the rules for handling large lists.
If a new column needs to be filtered on (and therefore needs to be indexed) then I'm force to export the list, delete rows until I'm < 5000 rows, add the index, and re-import the rows I deleted. This process as currently done is very slow (days) because it is done with non-optimized CSOM code that copies to/from a SQL database. An additional challenge is that the rules of large lists make it more difficult to write queries to identify 70K+ rows to use in the process.
My question is this: How can I more quickly copy >70k rows to a temporary location, delete them, and then after indexing, moving the rows back to the original list? Does Sharepoint support any form of quickly moving items to another table? Are there any bulk import/export utilities for situations like this?