kvdb-rocksdb: set format_version to 5

[ordian]

The block_restart_interval is set in accordance with https://rocksdb.org/blog/2019/03/08/format-version-4.html.

Context: https://github.com/facebook/rocksdb/blob/a1523efcdf2f0e8133b9a9f6e170a0dad49f928f/include/rocksdb/table.h#L246-L271

This change is backwards compatible with rocksdb versions >= 6.6.

// This option only affects newly written tables. When reading existing
// tables, the information about version is read from the footer.

[dvdplm]

Context: https://github.com/facebook/rocksdb/blob/a1523efcdf2f0e8133b9a9f6e170a0dad49f928f/include/rocksdb/table.h#L246-L271

Given the outcome of our experiments with version 5 it seems likely that this also is effective only for new tables, do you agree?

[ordian]

Context: https://github.com/facebook/rocksdb/blob/a1523efcdf2f0e8133b9a9f6e170a0dad49f928f/include/rocksdb/table.h#L246-L271

Given the outcome of our experiments with version 5 it seems likely that this also is effective only for new tables, do you agree?

yeah, it's explicitly mentioned in version 3 and 4

// This option only affects newly written tables. When reading existing
// tables, the information about version is read from the footer.

[dvdplm]

@NikVolf can you take a look at this please? Would be good to include this before we merge #402

[NikVolf]

Why is it needed?

Sorry, missed this thing for a while 😔

[ordian]

version 5 introduces improvements to bloom filter https://github.com/facebook/rocksdb/wiki/RocksDB-Bloom-Filter#full-filters-new-format

[ordian]

the default version in librocksdb-sys 6.7.4 (the latest published one) is 2 https://github.com/facebook/rocksdb/blob/27e593fbe10efa5a562ca79b1939ffb69d25163f/include/rocksdb/table.h#L275
in librocksdb-sys 6.10.1, which is merged in master, but not published, it's 4: https://github.com/facebook/rocksdb/blob/1482c8697c260cc12f7fce9f15401a85330d2ff1/include/rocksdb/table.h#L272

[NikVolf]

I hope this get tested on the database created without this update

[ordian]

I just tested this with openethereum, it worked.