Summary:
Some specific old versions around RocksDB 2.5 would compress the metaindex and properties blocks. This hasn't been done since, probably because it interferes with the properties block indicating how to set up for decompression (so the reader can read those blocks before doing any decompression).
To fix backward compatibility, we establish a decompressor early if format_version indicates the file could come from a sufficiently old version.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/13628
Test Plan: local and CI runs of tools/check_format_compatible.sh. (I don't believe we need special code to set up a unit test for this case.)
Reviewed By: jowlyzhang
Differential Revision: D75107623
Pulled By: pdillinger
fbshipit-source-id: 97132b8c5e0602e8e27254a11386d866b23cb4f5
cda1e40498