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[已解决] 无需改写SQL和加索引，GreatSQL Rapid引擎一招优化提升1300多倍

785 2 2024-4-16 15:13
原始案例：记一个优化SQL (qq.com)


在上述案例中，我在复现过程中，两个测试表均填充10万条记录，执行计划如下


  3. *************************** 1. row ***************************
  4.            id: 1
  5.   select_type: PRIMARY
  6.         table: t
  7.    partitions: NULL
  8.          type: ALL
  9. possible_keys: NULL
  10.           key: NULL
  11.       key_len: NULL
  12.           ref: NULL
  13.          rows: 100010
  14.      filtered: 100.00
  15.         Extra: NULL
  16. *************************** 2. row ***************************
  17.            id: 2
  18.   select_type: DEPENDENT SUBQUERY
  19.         table: s
  20.    partitions: NULL
  21.          type: ref
  22. possible_keys: idx_de3_n1
  23.           key: idx_de3_n1
  24.       key_len: 19
  25.           ref: sbtest.t.dept_no
  26.          rows: 594
  27.      filtered: 11.11
  28.         Extra: Using index condition; Using where




  33. | -> Table scan on t  (cost=9934.85 rows=98626) (actual time=0.028..30.044 rows=100000 loops=1)
  34. -> Select #2 (subquery in projection; dependent)
  35.     -> Aggregate: count(s.to_date)  (cost=160.68 rows=1) (actual time=1.159..1.159 rows=1 loops=100000)
  36.         -> Filter: ((s.from_date >= '1900-01-03') and (s.from_date <= '1985-01-01'))  (cost=154.13 rows=66) (actual time=1.159..1.159 rows=0 loops=100000)
  37.             -> Index lookup on s using idx_de3_n1 (dept_no=t.dept_no), with index condition: (s.dept_no = t.dept_no)  (cost=154.13 rows=590) (actual time=0.160..1.103 rows=676 loops=100000)

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这条SQL在测试环境中耗时 113秒，详情见下：


  3. # Query_time: 113.026347  Lock_time: 0.000002 Rows_sent: 100000  Rows_examined: 67747561 Thread_id: 4355 Errno: 0 Killed: 0 Bytes_received: 189 Bytes_sent: 4935625 Read_first: 1 Read_last: 0 Read_key: 100001 Read_next: 67647561 Read_prev: 0 Read_rnd: 0 Read_rnd_next: 100001 Sort_merge_passes: 0 Sort_range_count: 0 Sort_rows: 0 Sort_scan_count: 0 Created_tmp_disk_tables: 0 Created_tmp_tables: 0 Start: 2024-04-16T14:57:47.921731+08:00 End: 2024-04-16T14:59:40.948078+08:00 Schema: sbtest Rows_affected: 0
  4. # Tmp_tables: 0  Tmp_disk_tables: 0  Tmp_table_sizes: 0
  5. # InnoDB_trx_id: 0
  6. # Full_scan: Yes  Full_join: No  Tmp_table: No  Tmp_table_on_disk: No
  7. # Filesort: No  Filesort_on_disk: No  Merge_passes: 0
  8. #   InnoDB_IO_r_ops: 0  InnoDB_IO_r_bytes: 0  InnoDB_IO_r_wait: 0.000000
  9. #   InnoDB_rec_lock_wait: 0.000000  InnoDB_queue_wait: 0.000000
  10. #   InnoDB_pages_distinct: 873
  11. SET timestamp=1713250455;
  12. select *  ,(select count(to_date) from dept_emp5 s force index(idx_de3_n1)   where s.dept_no = t.dept_no and from_date >='1900-01-03'  and from_date <= '1985-01-01') s from t_group t;

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由于t_group表需要全表扫描所以特别慢，可以看到总共需要扫描 67747561 行记录，但只返回10万条记录，所以特别慢。

这个案例我改成用Rapid引擎来跑，同样环境下，只需要耗时 0.08秒，性能提升1366倍，在这个过程中完全无需改写SQL、调整优化参数等额外动作，详情见下：


  3. # Query_time: 0.082696  Lock_time: 0.000002 Rows_sent: 100000  Rows_examined: 0 Thread_id: 4355 Errno: 0 Killed: 0 Bytes_received: 189 Bytes_sent: 4935523 Read_first: 0 Read_last: 0 Read_key: 0 Read_next: 0 Read_prev: 0 Read_rnd: 0 Read_rnd_next: 0 Sort_merge_passes: 0 Sort_range_count: 0 Sort_rows: 0 Sort_scan_count: 0 Created_tmp_disk_tables: 0 Created_tmp_tables: 0 Start: 2024-04-16T15:02:37.423297+08:00 End: 2024-04-16T15:02:37.505993+08:00 Schema: sbtest Rows_affected: 0
  4. # Tmp_tables: 0  Tmp_disk_tables: 0  Tmp_table_sizes: 0
  5. # Full_scan: Yes  Full_join: Yes  Tmp_table: No  Tmp_table_on_disk: No
  6. # Filesort: No  Filesort_on_disk: No  Merge_passes: 0

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另一个SQL优化案例参考：SQL优化案例解析：MINUS改写为标量子查询后提升5倍，但还可以再快近百倍 (qq.com)。

关于GreatSQL Rapid引擎详情参考：Rapid引擎（Rapid Engine） | GreatSQL用户手册。
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yejr 2024-4-16 16:03:56
这是另一个优化案例：SQL 优化案例_(1) (qq.com)


在本案中，我填充了100万行测试数据，下面是对比结果

原始SQL运行了387秒还没结束，被我CTRL+C强制终止：


  3. # Query_time: 387.640089  Lock_time: 0.000002 Rows_sent: 0  Rows_examined: 1755869365 Thread_id: 4355 Errno: 1317 Killed: 0 Bytes_received: 663 Bytes_sent: 266 Read_first: 1757 Read_last: 0 Read_key: 1757 Read_next: 0 Read_prev: 0 Read_rnd: 0 Read_rnd_next: 1755871120 Sort_merge_passes: 0 Sort_range_count: 0 Sort_rows: 0 Sort_scan_count: 0 Created_tmp_disk_tables: 0 Created_tmp_tables: 1 Start: 2024-04-16T15:39:48.025906+08:00 End: 2024-04-16T15:46:15.665995+08:00 Schema: sbtest Rows_affected: 0
  4. # Tmp_tables: 1  Tmp_disk_tables: 0  Tmp_table_sizes: 85880
  5. # InnoDB_trx_id: 0
  6. # Full_scan: Yes  Full_join: No  Tmp_table: Yes  Tmp_table_on_disk: No
  7. # Filesort: No  Filesort_on_disk: No  Merge_passes: 0
  8. #   InnoDB_IO_r_ops: 0  InnoDB_IO_r_bytes: 0  InnoDB_IO_r_wait: 0.000000
  9. #   InnoDB_rec_lock_wait: 0.000000  InnoDB_queue_wait: 0.000000
  10. #   InnoDB_pages_distinct: 7485
  11. SET timestamp=1713253188;
  12. select S.syctime_day,
  13. (select count(*) from t1 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'CDE',
  14. (select count(*) from t1 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'SDE',
  15. (select count(*) from t1 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'PDE',
  16. (select count(*) from t1 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'CSE',
  17. (select count(*) from t1 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'SSE'
  18. from t1 S where S.syctime_day > '2024-01-01' and S.syctime_day < '2024-08-01'
  19. GROUP BY S.syctime_day order by S.syctime_day asc;

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改用Rapid引擎（无需改写SQL、无需添加索引等额外工作）后，秒出结果，详情如下：


  3. # Query_time: 0.022815  Lock_time: 0.000003 Rows_sent: 1  Rows_examined: 0 Thread_id: 4355 Errno: 0 Killed: 0 Bytes_received: 662 Bytes_sent: 223 Read_first: 0 Read_last: 0 Read_key: 0 Read_next: 0 Read_prev: 0 Read_rnd: 0 Read_rnd_next: 0 Sort_merge_passes: 0 Sort_range_count: 0 Sort_rows: 0 Sort_scan_count: 0 Created_tmp_disk_tables: 0 Created_tmp_tables: 0 Start: 2024-04-16T15:57:40.723431+08:00 End: 2024-04-16T15:57:40.746246+08:00 Schema: sbtest Rows_affected: 0
  4. # Tmp_tables: 0  Tmp_disk_tables: 0  Tmp_table_sizes: 0
  5. # Full_scan: Yes  Full_join: Yes  Tmp_table: No  Tmp_table_on_disk: No
  6. # Filesort: No  Filesort_on_disk: No  Merge_passes: 0
  7. # No InnoDB statistics available for this query
  8. SET timestamp=1713254260;
  9. select S.syctime_day,
  10. (select count(*) from t2 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'CDE',
  11. (select count(*) from t2 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'SDE',
  12. (select count(*) from t2 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'PDE',
  13. (select count(*) from t2 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'CSE',
  14. (select count(*) from t2 SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'SSE'
  15. from t2 S where S.syctime_day > '2024-01-01' and S.syctime_day < '2024-08-01'

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效率提升不止数万倍。

以上。

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yejr 2024-4-17 10:39:40
传统SQL优化案例：GreatSQL优化技巧：半连接(semijoin)优化，在这个案例中，如果采用GreatSQL Rapid引擎，则相比原始SQL提升120倍，相比优化后的SQL提升18倍
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