| # Doris reads data through the Thrift interface |
| ## Scenes |
| It is necessary to read a large amount of data, and spark/flink connectors use this method to read data. |
| ## process |
| ### 1. Query the corresponding queryPlan according to SQL |
| Call api：/api/<db>/<table>/_query_plan |
| Specifically, can see: https://doris.apache.org/zh-CN/docs/dev/admin-manual/http-actions/fe/table-query-plan-action |
| This interface will return the tabletID hit by the corresponding SQL and the distributed backend information |
| |
| ### 2. Access backend and read tablet data directly |
| Interact with BE through Thrift interface, Thrift interface definition can be seen TDorisExternalService |
| #### 2.1 doris will build a scan context for this session, context_id returned if success |
| TScanOpenResult open(1: TScanOpenParams params); |
| |
| #### 2.2 return the batch_size of data |
| TScanBatchResult getNext(1: TScanNextBatchParams params); |
| |
| #### 2.3 release the context resource associated with the context_id |
| TScanCloseResult close(1: TScanCloseParams params); |
| |
| ### 3. Convert Arrow data |
| Read data through Arrow and convert it to row data |
| |
| For more design documents, please refer to: https://github.com/apache/doris/issues/1525 |
