深入解析MySQL分区（Partition）功能(二)
re c3 > date '1995-01-01' and c3 < date '1995-12-31'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: part_tab
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 798458
Extra: Using where
1 row in set (0.00 sec)
explain语句显示了SQL查询要处理的记录数目
* 试验创建索引后情况
[sql]
mysql> create index idx_of_c3 on no_part_tab (c3);
Query OK, 8000000 rows affected (1 min 18.08 sec)
Records: 8000000 Duplicates: 0 Warnings: 0
[sql]
mysql> create index idx_of_c3 on part_tab (c3);
Query OK, 8000000 rows affected (1 min 19.19 sec)
Records: 8000000 Duplicates: 0 Warnings: 0
创建索引后的
数据库文件大小列表：
2008-05-24 09:23 8,608 no_part_tab.frm
2008-05-24 09:24 255,999,996 no_part_tab.MYD
2008-05-24 09:24 81,611,776 no_part_tab.MYI
2008-05-24 09:25 0 part_tab#P#p0.MYD
2008-05-24 09:26 1,024 part_tab#P#p0.MYI
2008-05-24 09:26 25,550,656 part_tab#P#p1.MYD
2008-05-24 09:26 8,148,992 part_tab#P#p1.MYI
2008-05-24 09:26 25,620,192 part_tab#P#p10.MYD
2008-05-24 09:26 8,170,496 part_tab#P#p10.MYI
2008-05-24 09:25 0 part_tab#P#p11.MYD
2008-05-24 09:26 1,024 part_tab#P#p11.MYI
2008-05-24 09:26 25,656,512 part_tab#P#p2.MYD
2008-05-24 09:26 8,181,760 part_tab#P#p2.MYI
2008-05-24 09:26 25,586,880 part_tab#P#p3.MYD
2008-05-24 09:26 8,160,256 part_tab#P#p3.MYI
2008-05-24 09:26 25,585,696 part_tab#P#p4.MYD
2008-05-24 09:26 8,159,232 part_tab#P#p4.MYI
2008-05-24 09:26 25,585,216 part_tab#P#p5.MYD
2008-05-24 09:26 8,159,232 part_tab#P#p5.MYI
2008-05-24 09:26 25,655,740 part_tab#P#p6.MYD
2008-05-24 09:26 25,586,528 part_tab#P#p7.MYD
2008-05-24 09:26 8,160,256 part_tab#P#p7.MYI
2008-05-24 09:26 25,586,752 part_tab#P#p8.MYD
2008-05-24 09:26 8,160,256 part_tab#P#p8.MYI
2008-05-24 09:26 25,585,824 part_tab#P#p9.MYD
2008-05-24 09:26 8,159,232 part_tab#P#p9.MYI
2008-05-24 09:25 8,608 part_tab.frm
2008-05-24 09:25 68 part_tab.par
* 再次测试SQL性能
[sql]
mysql> select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31';
+----------+
| count(*) |
+----------+
| 795181 |
+----------+
1 row in set (2.42 sec) /* 为原来4.69 sec 的51%*/
重启mysql ( net stop mysql, net start mysql)后，查询时间降为0.89 sec,几乎与分区表相同。
[sql]
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31';
+----------+
| count(*) |
+----------+
| 795181 |
+----------+
1 row in set (0.86 sec)
* 更进一步的试验
** 增加日期范围
[sql]
mysql> select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1997-12-31';
+----------+
| count(*) |
+----------+
| 2396524 |
+----------+
1 row in set (5.42 sec)
[sql]
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date '1997-12-31';
+----------+
| count(*) |
+----------+
| 2396524 |
+----------+
1 row in set (2.63 sec)
** 增加未索引字段查询
[sql]
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date
'1996-12-31' and c2='hello';
+----------+
| count(*) |
+----------+