apache
Revert required SegmentInfos min version in header check in readCommit to continue binary compatibility with 8.x indexes
Description
#14607 advanced the SegmentInfos version to VERSION_86 (10) in header check during readCommit() to allow tests to find backward codecs until 9.x while throwing a graceful IndexFormatTooOldException for indexes < v8.6.0 (since by default anything < 10x is "too old"). Earlier with VERSION_74 (9), readCodec() would throw an IllegalArgumentException since readCommit now checks for segment level compatibility instead of looking at when the index was first created, and would find the 7.x codecs missing for some of the old indexes. This was causing some of the tests to fail.
However #15431 made me realize that we can afford to allow binary readability on 8.x indexes like was the case previously and also keep the tests happy., This change would also help keep the core logic and constraints consistent across 10x and main.
Hi @msokolov , gentle reminder for whenever you are able to get to this. Thank you.
