Question

这是我运行的日志。随着intarray关闭，它运行在56毫秒。然后我启用了intarray，并运行相同的查询，而且速度要慢得多。

启用扩展程序后，是否需要重新索引表格或类似内容？

db.Query("SELECT COUNT(*) FROM some_tbl")

这是tutor_topic表的架构;

test_int=# explain analyze select * from tutor_topic tt1 where tt1.topic_id @> '{5,7,8,9}';
                                                      QUERY PLAN                                                       
-----------------------------------------------------------------------------------------------------------------------
 Seq Scan on tutor_topic tt1  (cost=0.00..29742.00 rows=1000 width=105) (actual time=24.903..1937.480 rows=68 loops=1)
   Filter: (topic_id @> '{5,7,8,9}'::integer[])
   Rows Removed by Filter: 999932
 Planning time: 0.084 ms
 Execution time: 1937.521 ms
(5 rows)

Time: 1938.000 ms
test_int=# DROP EXTENSION intarray;                                                                                                                              DROP EXTENSION
Time: 10.516 ms
test_int=# explain analyze select * from tutor_topic tt1 where tt1.topic_id @> '{5,7,8,9}';
                                                            QUERY PLAN                                                            
----------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on tutor_topic tt1  (cost=108.78..487.18 rows=100 width=105) (actual time=55.063..55.138 rows=68 loops=1)
   Recheck Cond: (topic_id @> '{5,7,8,9}'::integer[])
   Heap Blocks: exact=68
   ->  Bitmap Index Scan on message_rdtree_idx  (cost=0.00..108.75 rows=100 width=0) (actual time=55.047..55.047 rows=68 loops=1)
         Index Cond: (topic_id @> '{5,7,8,9}'::integer[])
 Planning time: 0.196 ms
 Execution time: 55.180 ms
(7 rows)

Time: 56.095 ms
test_int=#

这些是指数：

CREATE TABLE IF NOT EXISTS tutor_topic                                               
(                                                                                    
      tutor_id              INT NOT NULL,                                            
      topic_id              INT[]                                                    
);

Answer 1

我想出了答案！

创建索引时，我需要从扩展名中指定功能： CREATE INDEX message_rdtree_idx ON tutor_topic使用GIN（topic_id gin__int_ops）;

现在表现匹配。从explain analyze调用来看，似乎根本没有使用索引。

为什么在PostgreSQL上启用intarray扩展导致性能下降10倍？

1 个答案: