Identify what a ".save" file is and its purpose

After deleting some documents from an index, I noticed a compound-file (.cfs) .save file extension as in . I have looked for this file in open source docs/searches and within the community, but I have been unable to identify anything that viably explains what this file does or is.

Has anyone come across this file type and/or know what its use is?

Thank you in advance.

I'm pretty sure this isn't a file created by Elasticsearch - at least, I can see no reference to this extension anywhere in the source code, and I've never seen such a file before. This indicates there's a pretty serious problem with your setup, see these docs:

WARNING: Don’t modify anything within the data directory or run processes that might interfere with its contents. If something other than Elasticsearch modifies the contents of the data directory, then Elasticsearch may fail, reporting corruption or other data inconsistencies, or may appear to work correctly having silently lost some of your data.


Thanks, David.