EXPLAIN 生成的查询计划

EXPLAIN 返回用于执行指定查询的优化器查询计划。例如：

 QUERY PLAN DESCRIPTION:
 ------------------------------

 EXPLAIN SELECT customer_name, customer_state FROM customer_dimension WHERE customer_state IN ('MA','NH') AND customer_gender='Male' ORDER BY customer_name LIMIT 10;

 Access Path:
 +-SELECT  LIMIT 10 [Cost: 365, Rows: 10] (PATH ID: 0)
 |  Output Only: 10 tuples
 |  Execute on: Query Initiator
 | +---> SORT [TOPK] [Cost: 365, Rows: 544] (PATH ID: 1)
 | |      Order: customer_dimension.customer_name ASC
 | |      Output Only: 10 tuples
 | |      Execute on: Query Initiator
 | | +---> STORAGE ACCESS for customer_dimension [Cost: 326, Rows: 544] (PATH ID: 2)
 | | |      Projection: public.customer_dimension_DBD_1_rep_VMartDesign_node0001
 | | |      Materialize: customer_dimension.customer_state, customer_dimension.customer_name
 | | |      Filter: (customer_dimension.customer_gender = 'Male')
 | | |      Filter: (customer_dimension.customer_state = ANY (ARRAY['MA', 'NH']))
 | | |      Execute on: Query Initiator
 | | |      Runtime Filter: (SIP1(TopK): customer_dimension.customer_name)

您可以使用 EXPLAIN 评估优化器做出的关于给定查询的选择。如果您认为查询性能未达到最佳效果，请通过 Database Designer 运行该查询。有关详细信息，请参阅增量设计和缩短查询运行时间。