When compacting several sstables, get and merge their encoding_stats
for encoding the result.
Introduce sstable::get_encoding_stats_for_compaction to return encoding_stats
based on the sstable's column stats.
Use encoding_stats_collector to keep track of the minimum encoding_stats
values of all input sstables.
Fixes#3971
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
We keep track of all updates and store the minimal values of timestamps,
TTLs and local deletion times across all the inserted data.
These values are written as a part of serialization_header for
Statistics.db and used for delta-encoding values when writing Data.db
file in SSTables 3.0 (mc) format.
For #1969.
Signed-off-by: Vladimir Krivopalov <vladimir@scylladb.com>
