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我是 MySQL 新手。我有一个具有以下结构的表:
CREATE TABLE `gc_ads` (
`n` int(10) unsigned NOT NULL DEFAULT '0',
`title` varchar(255) NOT NULL DEFAULT '',
`detail` text NOT NULL,
`c` char(6) DEFAULT NULL,
`c_path` char(24) DEFAULT NULL,
`a` char(8) DEFAULT NULL,
`a_path` char(32) DEFAULT NULL,
`created` int(10) unsigned NOT NULL DEFAULT '0',
`edited` int(10) unsigned NOT NULL DEFAULT '0',
`t1` int(10) unsigned NOT NULL DEFAULT '0',
`t2` int(10) unsigned NOT NULL DEFAULT '0',
`status` set('waiting','enabled','disabled','queue','wait','preview') NOT NULL DEFAULT '',
`en_cats` tinyint(1) NOT NULL DEFAULT '0',
`home_page` int(10) unsigned NOT NULL DEFAULT '0',
PRIMARY KEY (`n`,`t1`,`t2`,`status`,`en_cats`),
KEY `home_page_featured` (`status`,`home_page`),
KEY `recount_index` (`c_path`,`a_path`,`t1`,`t2`,`status`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8
我需要运行以下查询:
select * from gc_ads where c_path in ("_9_","_9_30_","_9_101_","_9_102_","_9_103_","_9_105_","_9_106_","_9_30_132_","_9_30_133_","_9_30_134_","_9_30_135_","_9_30_136_","_9_30_137_","_9_30_138_","_9_30_139_","_9_30_140_","_9_30_141_","_9_30_142_","_9_30_143_","_9_30_144_","_9_30_145_","_9_30_146_","_9_30_147_","_9_30_148_","_9_30_149_","_9_30_150_","_9_30_151_","_9_30_152_","_9_30_153_","_9_30_154_","_9_30_155_","_9_30_156_","_9_30_157_","_9_30_158_","_9_30_159_","_9_30_160_","_9_30_161_","_9_30_162_","_9_101_222_","_9_101_221_","_9_101_220_","_9_101_219_","_9_101_218_","_9_101_217_","_9_101_216_","_9_101_215_","_9_101_214_","_9_101_213_","_9_101_212_","_9_101_211_","_9_101_210_","_9_101_209_","_9_101_208_","_9_101_207_","_9_101_206_","_9_101_205_","_9_101_204_","_9_101_203_","_9_101_202_","_9_101_201_","_9_101_200_","_9_101_199_","_9_101_198_","_9_101_196_","_9_101_197_","_9_101_195_","_9_194_","_9_101_223_","_9_101_224_","_9_101_225_","_9_102_226_","_9_102_227_","_9_102_228_","_9_102_229_","_9_102_230_","_9_102_231_","_9_102_232_","_9_102_233_","_9_102_234_","_9_102_235_","_9_102_236_","_9_102_237_","_9_102_238_","_9_102_239_","_9_102_240_","_9_102_241_","_9_102_242_","_9_102_243_","_9_102_244_","_9_102_245_","_9_102_246_","_9_102_247_","_9_102_248_","_9_102_249_","_9_102_250_","_9_102_251_","_9_102_252_","_9_102_253_","_9_102_254_","_9_102_255_","_9_102_256_") and status='enabled' order by created desc limit 0,50;
此查询大约需要 0.38 秒,查询大约 60,000 条记录。我认为这非常慢。 Esplain 显示以下内容:
+----+-------------+--------+------+----------------------------------+--------------------+---------+-------+-------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------+------+----------------------------------+--------------------+---------+-------+-------+-----------------------------+
| 1 | SIMPLE | gc_ads | ref | recount_index,home_page_featured | home_page_featured | 1 | const | 34347 | Using where; Using filesort |
+----+-------------+--------+------+----------------------------------+--------------------+---------+-------+-------+-----------------------------+
如果我运行此查询(相同的查询,但其中没有“and status='enabled'”,则需要大约 0.10 秒:
select * from gc_ads use index(recount_index, home_page_featured) where c_path in ("_9_","_9_30_","_9_101_","_9_102_","_9_103_","_9_105_","_9_106_","_9_30_132_","_9_30_133_","_9_30_134_","_9_30_135_","_9_30_136_","_9_30_137_","_9_30_138_","_9_30_139_","_9_30_140_","_9_30_141_","_9_30_142_","_9_30_143_","_9_30_144_","_9_30_145_","_9_30_146_","_9_30_147_","_9_30_148_","_9_30_149_","_9_30_150_","_9_30_151_","_9_30_152_","_9_30_153_","_9_30_154_","_9_30_155_","_9_30_156_","_9_30_157_","_9_30_158_","_9_30_159_","_9_30_160_","_9_30_161_","_9_30_162_","_9_101_222_","_9_101_221_","_9_101_220_","_9_101_219_","_9_101_218_","_9_101_217_","_9_101_216_","_9_101_215_","_9_101_214_","_9_101_213_","_9_101_212_","_9_101_211_","_9_101_210_","_9_101_209_","_9_101_208_","_9_101_207_","_9_101_206_","_9_101_205_","_9_101_204_","_9_101_203_","_9_101_202_","_9_101_201_","_9_101_200_","_9_101_199_","_9_101_198_","_9_101_196_","_9_101_197_","_9_101_195_","_9_194_","_9_101_223_","_9_101_224_","_9_101_225_","_9_102_226_","_9_102_227_","_9_102_228_","_9_102_229_","_9_102_230_","_9_102_231_","_9_102_232_","_9_102_233_","_9_102_234_","_9_102_235_","_9_102_236_","_9_102_237_","_9_102_238_","_9_102_239_","_9_102_240_","_9_102_241_","_9_102_242_","_9_102_243_","_9_102_244_","_9_102_245_","_9_102_246_","_9_102_247_","_9_102_248_","_9_102_249_","_9_102_250_","_9_102_251_","_9_102_252_","_9_102_253_","_9_102_254_","_9_102_255_","_9_102_256_") order by created desc limit 0,50;
解释显示以下内容:
+----+-------------+--------+-------+---------------+---------------+---------+------+-------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------+-------+---------------+---------------+---------+------+-------+-----------------------------+
| 1 | SIMPLE | gc_ads | range | recount_index | recount_index | 73 | NULL | 14293 | Using where; Using filesort |
+----+-------------+--------+-------+---------------+---------------+---------+------+-------+-----------------------------+
如果我在没有“order by ...”的情况下运行查询,速度会非常快(0.01s):
select * from gc_ads use index(recount_index, home_page_featured) where c_path in ("_9_","_9_30_","_9_101_","_9_102_","_9_103_","_9_105_","_9_106_","_9_30_132_","_9_30_133_","_9_30_134_","_9_30_135_","_9_30_136_","_9_30_137_","_9_30_138_","_9_30_139_","_9_30_140_","_9_30_141_","_9_30_142_","_9_30_143_","_9_30_144_","_9_30_145_","_9_30_146_","_9_30_147_","_9_30_148_","_9_30_149_","_9_30_150_","_9_30_151_","_9_30_152_","_9_30_153_","_9_30_154_","_9_30_155_","_9_30_156_","_9_30_157_","_9_30_158_","_9_30_159_","_9_30_160_","_9_30_161_","_9_30_162_","_9_101_222_","_9_101_221_","_9_101_220_","_9_101_219_","_9_101_218_","_9_101_217_","_9_101_216_","_9_101_215_","_9_101_214_","_9_101_213_","_9_101_212_","_9_101_211_","_9_101_210_","_9_101_209_","_9_101_208_","_9_101_207_","_9_101_206_","_9_101_205_","_9_101_204_","_9_101_203_","_9_101_202_","_9_101_201_","_9_101_200_","_9_101_199_","_9_101_198_","_9_101_196_","_9_101_197_","_9_101_195_","_9_194_","_9_101_223_","_9_101_224_","_9_101_225_","_9_102_226_","_9_102_227_","_9_102_228_","_9_102_229_","_9_102_230_","_9_102_231_","_9_102_232_","_9_102_233_","_9_102_234_","_9_102_235_","_9_102_236_","_9_102_237_","_9_102_238_","_9_102_239_","_9_102_240_","_9_102_241_","_9_102_242_","_9_102_243_","_9_102_244_","_9_102_245_","_9_102_246_","_9_102_247_","_9_102_248_","_9_102_249_","_9_102_250_","_9_102_251_","_9_102_252_","_9_102_253_","_9_102_254_","_9_102_255_","_9_102_256_") limit 0,50;
解释显示以下内容:
+----+-------------+--------+-------+---------------+---------------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------+-------+---------------+---------------+---------+------+-------+-------------+
| 1 | SIMPLE | gc_ads | range | recount_index | recount_index | 73 | NULL | 14293 | Using where |
+----+-------------+--------+-------+---------------+---------------+---------+------+-------+-------------+
我猜我需要为此查询创建正确的索引,但我真的不知道如何开始解决这个问题。
最佳答案
这是您的查询:
select *
from gc_ads
where c_path in (. . .) and status='enabled'
order by created desc limit 0,50;
where
子句中的条件是 in
和相等。最好的索引是gc_ads(status, c_path,created)
。 where
子句可以使用前两个元素。 order by
可以使用最后一个。
recount_index
不太正确,因为它在 status
之前有两个附加元素。
关于mysql - 优化MySQL表结构,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18646188/
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