coprocessor: select response of dag don't need row meta.

src/coprocessor/dag/dag.rs

@@ -15,7 +15,7 @@ use std::rc::Rc;
 
 use tipb::executor::{ExecType, Executor};
 use tipb::schema::ColumnInfo;
-use tipb::select::{DAGRequest, RowMeta, SelectResponse};
+use tipb::select::{DAGRequest, SelectResponse};
 use kvproto::coprocessor::{KeyRange, Response};
 use protobuf::{Message as PbMsg, RepeatedField};
 
@@ -67,7 +67,6 @@ impl<'s> DAGContext<'s> {
                 Ok(Some(row)) => {
                     try!(self.req_ctx.check_if_outdated());
                     let chunk = get_chunk(&mut chunks);
-                    let length = chunk.get_rows_data().len();
                     if self.has_aggr {
                         chunk.mut_rows_data().extend_from_slice(&row.data.value);
                     } else {
@@ -78,10 +77,6 @@ impl<'s> DAGContext<'s> {
                         ));
                         chunk.mut_rows_data().extend_from_slice(&value);
                     }
-                    let mut meta = RowMeta::new();
-                    meta.set_handle(row.handle);
-                    meta.set_length((chunk.get_rows_data().len() - length) as i64);
-                    chunk.mut_rows_meta().push(meta);
                 }
                 Ok(None) => {
                     let mut resp = Response::new();

src/coprocessor/dag/executor/aggregation.rs

@@ -143,7 +143,9 @@ impl<'a> Executor for AggregationExecutor<'a> {
         let value_size = group_key.len() + approximate_size(&aggr_cols, false);
         let mut value = Vec::with_capacity(value_size);
         box_try!(value.encode(aggr_cols.as_slice(), false));
-        value.extend_from_slice(group_key);
+        if !self.group_by.is_empty() {
+            value.extend_from_slice(group_key);
+        }
         self.cursor += 1;
         Ok(Some(Row {
             handle: 0,