我創建了由一個日期列的幾個月這樣分區的MySQL表:MySQL的分區修剪PARTITION BY LIST
CREATE TABLE `my_big_table` (
`some_id` varchar(60) COLLATE utf8_unicode_ci NOT NULL,
`some_value` varchar(256) COLLATE utf8_unicode_ci NOT NULL,
`some_other_value` varchar(256) COLLATE utf8_unicode_ci NOT NULL,
`time` datetime NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
PARTITION BY LIST(MONTH(time))
(PARTITION p1 VALUES IN (1) ENGINE = MyISAM,
PARTITION p2 VALUES IN (2) ENGINE = MyISAM,
PARTITION p3 VALUES IN (3) ENGINE = MyISAM,
PARTITION p4 VALUES IN (4) ENGINE = MyISAM,
PARTITION p5 VALUES IN (5) ENGINE = MyISAM,
PARTITION p6 VALUES IN (6) ENGINE = MyISAM,
PARTITION p7 VALUES IN (7) ENGINE = MyISAM,
PARTITION p8 VALUES IN (8) ENGINE = MyISAM,
PARTITION p9 VALUES IN (9) ENGINE = MyISAM,
PARTITION p10 VALUES IN (10) ENGINE = MyISAM,
PARTITION p11 VALUES IN (11) ENGINE = MyISAM,
PARTITION p12 VALUES IN (12) ENGINE = MyISAM)
現在,當我運行
explain partitions select * from my_big_table where month(time) = 2 limit 10;
我得到的輸出:
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE my_big_table p1,p2,p3,p4,p5,p6,p7,p8,p9,p10,p11,p12 ALL NULL NULL NULL NULL 10762868 "Using where"
所以顯然所有的分區正在閱讀,我不知道爲什麼。不應該引擎足夠聰明以找出匹配值只能在分區p2?我得到相同的輸出爲基於日期的查詢,如
explain partitions select * from my_big_table where date(time) = '2013-02-01' limit 10;
任何線索?
乾杯,亞歷克斯