Open closed index with older version

Hi everyone,

I have doubts about how to retrieve documents from a closed index in older version of Elasticsearch.

Suppose we close an index because it is already out of the “online” query range and that index when we close it is in version 6.6.0 for example.

Suppose that within 1 or 2 we need to recover the documents of that index for legal needs or whatever and we are already in version 8.x or 9.x.

Initially the indexes are compatible with the previous major version, my question is what happens if it is 2 or 3 major versions older?

What are the possibilities to access these documents? because I think the versions will be incompatible and it will not be possible open the index directly and read the documents.

Thank you

That will indeed not be possible, so you will need to open and reindex a certain points.

First of all, thanks Christian!!

So, closed indexes should be taken into consideration when making upgrades.

Should only this process be done with closed indexes in the major version upgrades or every major o minor upgrade is made?

The process would it be… open, reindex, and close again?

Thanks again!!