# Execute and Read (Continue...)


![left](./student-guide/diagram/05-Read-execution-01-03.png)

------------------------------------------------------------
Finally, the query results will be return to the TiDB server, but the computation request that can be pushed to TiKV currently include TableScan, IndexScan, Selection, TopN, Limit, and PartialAggregation. Other more complex operators still need a single TiDB server. Therefore, it will be summarized in TiDB Server. After summarizing, the result set is formed. If it is a query operation, the result set (including Field list, row data) is written back to the client.

It should be mentioned here that in the execution of the read (2), part of the operator is pushed down to TiKV for execution, and the other part is finally summarized in the TiDB Server. As a result, there are two computational tasks (Tasks), which are Cop Tasks and Root Tasks, which are defined as follows:
  - CopTask is a physical plan that needs to be pushed down to the storage engine (TiKV) for computation. Each TiKV node that receives the request will do the same.
  - RootTask is the part of the physical plan that is calculated in TiDB.