mysql> select count(*) from id_renewal ;
+----------+
| count(*) |
+----------+
| 13633246 |
+----------+
执行输出需要 10 多分钟。这可以在服务器参数中进行调整吗？由于我应该每小时运行一次此查询以获取报告，因此查询需要 10 分钟对于我的业务人员来说是不可行的...
有没有像在 oracle 中那样在内存中保留的选项？
mysql> show variables like '%cache%';
+------------------------------+----------------------+
| Variable_name | Value |
+------------------------------+----------------------+
| binlog_cache_size | 32768 |
| have_query_cache | YES |
| key_cache_age_threshold | 300 |
| key_cache_block_size | 1024 |
| key_cache_division_limit | 100 |
| max_binlog_cache_size | 18446744073709547520 |
| query_cache_limit | 1048576 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 134217728 |
| query_cache_type | ON |
| query_cache_wlock_invalidate | OFF |
| table_definition_cache | 512 |
| table_open_cache | 2048 |
| thread_cache_size | 16 |
+------------------------------+----------------------+
14 rows in set (0.00 sec)
mysql> show global status like '%Qc%';
+-------------------------+-----------+
| Variable_name | Value |
+-------------------------+-----------+
| Qcache_free_blocks | 118 |
| Qcache_free_memory | 133367960 |
| Qcache_hits | 71077421 |
| Qcache_inserts | 137390744 |
| Qcache_lowmem_prunes | 18066 |
| Qcache_not_cached | 120209332 |
| Qcache_queries_in_cache | 427 |
| Qcache_total_blocks | 990 |
+-------------------------+-----------+
mysql> select count(*) from idea_sub_renewal ;
+----------+
| count(*) |
+----------+
| 13633246 |
+----------+
top - 17:40:19 up 148 days, 17:51, 10 users, load average: 0.83, 0.91, 1.00
Tasks: 257 total, 1 running, 251 sleeping, 0 stopped, 5 zombie
Cpu(s): 2.0%us, 0.6%sy, 0.0%ni, 97.1%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st
Mem: 8167348k total, 8124120k used, 43228k free, 33928k buffers
Swap: 16386260k total, 709864k used, 15676396k free, 4615456k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
26329 sym 19 0 1195m 64m 7456 S 13.3 0.8 66:34.40 java
12079 mysql 15 0 1725m 463m 4840 S 6.3 5.8 24227:57 mysqld
477 sym 18 0 674m 62m 7260 S 1.0 0.8 2:25.59 java
26948 powerdev 16 0 12896 1232 824 S 0.7 0.0 0:07.90 top
18843 sym 19 0 1271m 494m 7364 S 0.3 6.2 10:19.89 java
26379 sym 21 0 1203m 299m 7464 S 0.3 3.8 1:36.90 java
29872 sym 18 0 1238m 869m 7816 S 0.3 10.9 7:42.33 java
最佳答案
InnoDB COUNT() 对百万行的表运行缓慢。但是，如果您不使用 WHERE，则可以使用 hack 来查看表中有多少行 - 使用 EXPLAIN。
mysql> explain select count(1) from history;
+----+-------------+---------+-------+---------------+-----------+---------+------+----------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------+-------+---------------+-----------+---------+------+----------+-------------+
| 1 | SIMPLE | history | index | NULL | history_1 | 12 | NULL | 17227419 | Using index |
+----+-------------+---------+-------+---------------+-----------+---------+------+----------+-------------+
1 row in set (0.01 sec)
在“行”列中，您可以看到行数。
关于mysql count(*) 需要很长时间？有更好的选择吗？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11374913/