Create a batch of regions at once, usually used to create multiple logical
regions at once. Different engines can choose whether to support this
request. Metric Engine needs it.
Same as CreateRequests, but for dropping regions.
The column definition of a region. Unlike the message ColumnDef in
ddl.proto which is for clients outside GreptimeDB, this RegionColumnDef
is for region requests use only. So it carries an extra field column_id
that is known internally.
/ Regular compaction
/ Strictly-windowed compaction.