Replicated table-based routing for strong-consistency reads

Replicated table is a special table schema in OceanBase Database. A replicated table can read the latest data changes from any replica and applies to scenarios with low write frequency requirements but high read latency and read load balancing requirements. For more information about replicated tables, see Create a table.

Examples

1. Execute the following statement to create a replicated table:

   obclient [test]> CREATE TABLE TEST.DUP(C1 INT) DUPLICATE_SCOPE = 'cluster';
   

2. Provide the partitioning key value in the SQL statement to be executed.

   obclient [test]> SELECT * FROM TEST.DUP WHERE C1=123\G
   

3. Run the EXPLAIN ROUTE statement to view the routing process in OceanBase Database Proxy (ODP).

   obclient [test]> EXPLAIN ROUTE SELECT * FROM test.dup WHERE C1=123\G
   

   The following return result shows that ODP performs routing based on the DUP_REPLICA_FIRST routing strategy.

   ...
   > ROUTE_POLICY
     [INFO] Strong read duplicated table. Ignore proxy route policy and session route policy
   
   Route Plan
   -----------------
   > SQL_PARSE:{cmd:"COM_QUERY", table:"dup"}
   > ROUTE_INFO:{route_info_type:"USE_PARTITION_LOCATION_LOOKUP"}
   > LOCATION_CACHE_LOOKUP:{mode:"oceanbase"}
     > TABLE_ENTRY_LOOKUP_START:{}
       > FETCH_TABLE_RELATED_DATA:{table_entry:"not partition table or part info no exists"}
     > TABLE_ENTRY_LOOKUP_DONE:{table:"dup", table_id:500685, table_type:"USER TABLE", has_dup_replica:true}
   > ROUTE_POLICY:{replica:"10.10.10.2:50110", idc_type:"SAME_IDC", zone_type:"ReadWrite", role:"FOLLOWER", type:"FULL", is_dup_replica:true, is_partition_server:true, chosen_route_type:"ROUTE_TYPE_DUP_PARTITION_UNMERGE_LOCAL", route_policy:"DUP_REPLICA_FIRST", trans_consistency:"STRONG", session_consistency:"STRONG", proxy_idc_name:"zue"}
   > CONGESTION_CONTROL:{svr_addr:"10.10.10.2:50110"}