Split a tablet into primary key ranges by size

// A split key range request. Split tablet to key ranges, the request
// doesn't change layout of tablet.
message SplitKeyRangeRequestPB {
 required bytes tablet_id = 1;

 // Encoded primary key to begin scanning at (inclusive).
 optional bytes start_primary_key = 2 [(kudu.REDACT) = true];
 // Encoded primary key to stop scanning at (exclusive).
 optional bytes stop_primary_key = 3 [(kudu.REDACT) = true];

 // Number of bytes to try to return in each chunk. This is a hint.
 // The tablet server may return chunks larger or smaller than this value.
 optional uint64 target_chunk_size_bytes = 4;

 // The columns to consider when chunking.
 // If specified, then the size estimate used for 'target_chunk_size_bytes'
 // should only include these columns. This can be used if a query will
 // only scan a certain subset of the columns.
 repeated ColumnSchemaPB columns = 5;
}

// The primary key range of a Kudu tablet.
message KeyRangePB {
 // Encoded primary key to begin scanning at (inclusive).
 optional bytes start_primary_key = 1 [(kudu.REDACT) = true];
 // Encoded primary key to stop scanning at (exclusive).
 optional bytes stop_primary_key = 2 [(kudu.REDACT) = true];
 // Number of bytes in chunk.
 required uint64 size_bytes_estimates = 3;
}

message SplitKeyRangeResponsePB {
 // The error, if an error occurred with this request.
 optional TabletServerErrorPB error = 1;

 repeated KeyRangePB ranges = 2;
}