chore(sharding): fix sum prepare error (#389)

* fix(sharding): fix min max error

Signed-off-by: wangbo <wangbo@sphere-ex.com>

* feat(sharding): support sum

Signed-off-by: wangbo <wangbo@sphere-ex.com>

* chore(sharding): fix sum prepare

Signed-off-by: wangbo <wangbo@sphere-ex.com>

* chore(sharding): fix sum prepare

Signed-off-by: wangbo <wangbo@sphere-ex.com>

Signed-off-by: wangbo <wangbo@sphere-ex.com>
Co-authored-by: wangbo <wangbo@sphere-ex.com>

Author: wbtlb

pisa-proxy/runtime/mysql/src/server/executor.rs

@@ -461,6 +461,10 @@ where
                 _ => {}
             }
 
+            if chunk.par_iter().map(|x| &x[4..]).min() == chunk.par_iter().map(|x| &x[4..]).max() {
+                return Ok(())
+            }
+
             let chunk_data = &chunk[0];
             let ori_row_data = row_data.clone();
             let mut row_data = row_data.clone();