4
我正在做一个概念证明,我正在试验一个奇怪的行为。 我有一个按日期字段进行范围分区的表格,如果我设置了一个固定日期或由SYSDATE创建了一个查询,那么查询的成本会发生很大变化。oracle过滤器解释计划分区
这些在解释计划:
SQL> SELECT *
2 FROM TP_TEST_ELEMENTO_TRAZABLE ET
3 WHERE ET.FEC_RECEPCION
4 BETWEEN TRUNC(SYSDATE-2) AND TRUNC(SYSDATE-1)
5 ;
5109 filas seleccionadas.
Plan de Ejecuci¾n
----------------------------------------------------------
Plan hash value: 1151442660
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 5008 | 85136 | 4504 (8)| 00:00:55 | | |
|* 1 | FILTER | | | | | | | |
| 2 | PARTITION RANGE ITERATOR| | 5008 | 85136 | 4504 (8)| 00:00:55 | KEY | KEY |
|* 3 | TABLE ACCESS FULL | TP_TEST_ELEMENTO_TRAZABLE | 5008 | 85136 | 4504 (8)| 00:00:55 | KEY | KEY |
------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(TRUNC([email protected]!-2)<=TRUNC([email protected]!-1))
3 - filter("ET"."FEC_RECEPCION">=TRUNC([email protected]!-2) AND "ET"."FEC_RECEPCION"<=TRUNC([email protected]!-1))
EstadÝsticas
----------------------------------------------------------
1 recursive calls
0 db block gets
376 consistent gets
0 physical reads
0 redo size
137221 bytes sent via SQL*Net to client
4104 bytes received via SQL*Net from client
342 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
5109 rows processed
使用固定日期:
SQL> SELECT *
2 FROM TP_TEST_ELEMENTO_TRAZABLE ET
3 WHERE ET.FEC_RECEPCION
4 BETWEEN TO_DATE('26/02/2017', 'DD/MM/YYYY') AND TO_DATE('27/02/2017', 'DD/MM/YYYY')
5 ;
5109 filas seleccionadas.
Plan de Ejecuci¾n
----------------------------------------------------------
Plan hash value: 3903280660
-----------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
-----------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 5008 | 85136 | 11 (0)| 00:00:01 | | |
| 1 | PARTITION RANGE ITERATOR| | 5008 | 85136 | 11 (0)| 00:00:01 | 607 | 608 |
|* 2 | TABLE ACCESS FULL | TP_TEST_ELEMENTO_TRAZABLE | 5008 | 85136 | 11 (0)| 00:00:01 | 607 | 608 |
-----------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("ET"."FEC_RECEPCION"<=TO_DATE(' 2017-02-27 00:00:00', 'syyyy-mm-dd hh24:mi:ss'))
EstadÝsticas
----------------------------------------------------------
1 recursive calls
0 db block gets
376 consistent gets
0 physical reads
0 redo size
137221 bytes sent via SQL*Net to client
4104 bytes received via SQL*Net from client
342 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
5109 rows processed
那是什么产生的4504成本和11成本区别?
感谢提前:)
简短的回答是:“成本”并不意味着比较两个不同的查询(即使它们看起来非常相似);它们只是**,意味着一次比较一个查询的不同计划。比较不同的查询时,最好比较基数估计。 – mathguy
https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:313416745628 –
https://jonathanlewis.wordpress.com/2017/02/28/cost-是时,再次/ –