MySQL Query IN（）子句在索引列上速度较慢

php performance mysql

2022-08-30 19:41:54

我有一个由PHP脚本生成的MySQL查询，查询将如下所示：

SELECT * FROM Recipe_Data WHERE 404_Without_200 = 0 AND Failures_Without_Success = 0 AND RHD_No IN (10, 24, 34, 41, 43, 51, 57, 59, 61, 67, 84, 90, 272, 324, 402, 405, 414, 498, 500, 501, 510, 559, 562, 595, 632, 634, 640, 643, 647, 651, 703, 714, 719, 762, 765, 776, 796, 812, 814, 815, 822, 848, 853, 855, 858, 866, 891, 920, 947, 956, 962, 968, 1049, 1054, 1064, 1065, 1070, 1100, 1113, 1119, 1130, 1262, 1287, 1292, 1313, 1320, 1327, 1332, 1333, 1335, 1340, 1343, 1344, 1346, 1349, 1352, 1358, 1362, 1365, 1482, 1495, 1532, 1533, 1537, 1549, 1550, 1569, 1571, 1573, 1574, 1596, 1628, 1691, 1714, 1720, 1735, 1755, 1759, 1829, 1837, 1844, 1881, 1919, 2005, 2022, 2034, 2035, 2039, 2054, 2076, 2079, 2087, 2088, 2089, 2090, 2091, 2092, 2154, 2155, 2156, 2157, 2160, 2162, 2164, 2166, 2169, 2171, 2174, 2176, 2178, 2179, 2183, 2185, 2186, 2187, 2201, 2234, 2236, 2244, 2245, 2250, 2255, 2260, 2272, 2280, 2281, 2282, 2291, 2329, 2357, 2375, 2444, 2451, 2452, 2453, 2454, 2456, 2457, 2460, 2462, 2464, 2465, 2467, 2468, 2469, 2470, 2473, 2474, 2481, 2485, 2487, 2510, 2516, 2519, 2525, 2540, 2545, 2547, 2553, 2571, 2579, 2580, 2587, 2589, 2597, 2602, 2611, 2629, 2660, 2662, 2700, 2756, 2825, 2833, 2835, 2858, 2958, 2963, 2964, 3009, 3090, 3117, 3118, 3120, 3121, 3122, 3123, 3126, 3127, 3129, 3130, 3133, 3135, 3137, 3138, 3139, 3141, 3142, 3145, 3146, 3147, 3151, 3152, 3155, 3193, 3201, 3204, 3219, 3221, 3222, 3223, 3224, 3225, 3226, 3227, 3228, 3229, 3231, 3232, 3233, 3234, 3235, 3237, 3239, 3246, 3250, 3253, 3259, 3261, 3291, 3315, 3328, 3377, 3381, 3383, 3384, 3385, 3387, 3388, 3389, 3390, 3396, 3436, 3463, 3465, 3467, 3470, 3471, 3484, 3507, 3515, 3554, 3572, 3641, 3672, 3683, 3689, 3690, 3692, 3693, 3694, 3697, 3698, 3705, 3711, 3713, 3715, 3716, 3717, 3719, 3720, 3722, 3726, 3727, 3732, 3737, 3763, 3767, 3770, 3771, 3772, 3773, 3803, 3810, 3812, 3816, 3846, 3847, 3848, 3851, 3874, 3882, 3902, 3903, 3906, 3908, 3916, 3924, 3967, 3987, 4006, 4030, 4043, 4045, 4047, 4058, 4067, 4107, 4108, 4114, 4115, 4131, 4132, 4133, 4137, 4138, 4139, 4140, 4141, 4142, 4146, 4150, 4151, 4152, 4153, 4157, 4158, 4160, 4163, 4166, 4167, 4171, 4179, 4183, 4221, 4225, 4242, 4257, 4435, 4437, 4438, 4443, 4446, 4449, 4450, 4451, 4452, 4454, 4460, 4550, 4557, 4618, 4731, 4775, 4804, 4972, 5025, 5026, 5039, 5042, 5294, 5578, 5580, 5599, 5602, 5649, 5726, 5779, 5783, 5931, 5934, 5936, 5939, 5940, 5941, 5978, 6044, 6056, 6113, 6116, 6118, 6122, 6123, 6125, 6127, 6128, 6129, 6130, 6131, 6135, 6141, 6145, 6147, 6150, 6152, 6153, 6154, 6160, 6166, 6169);

RHD_No列是此数据库的主键，总共大约有 400，000 行。问题是，查询非常慢，通常大约在2秒左右，但我看到它长到10秒。

当我尝试解释查询时，一切似乎都应该没问题：

+----+-------------+-------------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table       | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+-------------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | Recipe_Data | range | PRIMARY       | PRIMARY | 4       | NULL |  420 | Using where |
+----+-------------+-------------+-------+---------------+---------+---------+------+------+-------------+

当我分析查询时，我得到：

mysql> show profile;
+--------------------------------+----------+
| Status                         | Duration |
+--------------------------------+----------+
| starting                       | 0.000015 |
| checking query cache for query | 0.000266 |
| Opening tables                 | 0.000009 |
| System lock                    | 0.000004 |
| Table lock                     | 0.000006 |
| init                           | 0.000115 |
| optimizing                     | 0.000038 |
| statistics                     | 0.000797 |
| preparing                      | 0.000047 |
| executing                      | 0.000002 |
| Sending data                   | 2.675270 |
| end                            | 0.000007 |
| query end                      | 0.000003 |
| freeing items                  | 0.000071 |
| logging slow query             | 0.000002 |
| logging slow query             | 0.000058 |
| cleaning up                    | 0.000005 |
+--------------------------------+----------+

我已经在这个问题上工作了很长时间，但我无法找到解决方案。此查询是否有任何明显的错误？我不明白看420行应该需要2+秒。

答案 1

您正在按主键访问 420 行，这可能会导致索引访问路径。这可以访问 2 个索引页和每个键一个数据页。如果这些在缓存中，则查询应快速运行。否则，进入磁盘的每个页面访问都会导致通常的磁盘延迟。如果我们假设 5 毫秒的磁盘延迟和 80% 的缓存命中率，则得出 420*3*0.2*5ms=1.2 秒，这与你所看到的大致相同。

答案 2

问题是，这基本上被视为一堆s（例如INOR

col IN (1,2,3)

是

col = 1 OR col = 2 OR col = 3

这比联接慢很多。

您应该做的是生成创建临时表的 SQL 代码，使用“IN”子句中的值填充它，然后与该临时表联接

CREATE TEMPORARY TABLE numbers (n INT)

然后在循环中，添加

INSERT numbers  VALUES ($next_number)

然后在最后

SELECT * FROM numbers, Recipe_Data 
WHERE numbers.n = RHD_No

MySQL Query IN（） 子句在索引列上速度较慢

MySQL Query IN（）子句在索引列上速度较慢