query_cache_type = 1
query_cache_size = 600000

set global query_cache_type = 1; 
set global query_cache_size = 600000;

[[email protected] ~]$ MySQL -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or /g.
Your MySQL connection id is 3
Server version: 5.0.45-community MySQL Community Edition (GPL)
Type 'help;' or '/h' for help. Type '/c' to clear the buffer.
MySQL> set global query_cache_size = 600000;

設定快取記憶體

Query OK, 0 rows affected (0.00 sec)
MySQL> set session query_cache_type = ON;

開啟查詢快取

Query OK, 0 rows affected (0.00 sec)
MySQL> use test Reading table information for completion
of table and column names You can turn off this feature to
get a quicker startup with -A Database changed mysql> show tables;
+----------------+ | Tables_in_test | +----------------+ | animals |
| person | +----------------+ 5 rows in set (0.00 sec)
mysql>

Qcache_hits表示mysql快取查詢在快取中命中的累計次數，是累加值。

mysql> SHOW STATUS LIKE 'Qcache_hits'; +---------------+-------+
| Variable_name | Value | +---------------+-------+ | Qcache_hits
| 0 | --0次 +---------------+-------+ 8 rows in set (0.00 sec)
mysql> select count(*) from animals; +----------+ | count(*)
| +----------+ | 6 | +----------+ 1 row in set (0.00 sec)
mysql> SHOW STATUS LIKE 'Qcache%'; +---------------+-------+
| Variable_name | Value | +---------------+-------+ | Qcache_hits | 1 | 

表示sql在快取中直接得到結果，不需要再去解析

+---------------+-------+ 8 rows in set (0.00 sec)
mysql> select count(*) from animals; +----------+
| count(*) | +----------+ | 6 | +----------+ 1 row in set (0.00 sec)
mysql> select count(*) from animals; +----------+ | count(*)
| +----------+ | 6 | +----------+ 1 row in set (0.00 sec)
mysql> SHOW STATUS LIKE 'Qcache_hits'; +---------------+-------+
| Variable_name | Value | +---------------+-------+ | Qcache_hits | 3 | 

上面的sql也是是從快取中直接取到結果

+---------------+-------+ 1 row in set (0.00 sec) mysql> insert into animals select 9,'testsds' ; 

插入資料後，跟這個表所有相關的sql快取就會被清空掉

Query OK, 1 row affected (0.00 sec) Records:
1 Duplicates: 0 Warnings: 0 mysql> select count(*) from animals;
+----------+ | count(*) | +----------+ | 7 | +----------+
1 row in set (0.00 sec) mysql> SHOW STATUS LIKE 'Qcache_hits';
+---------------+-------+ | Variable_name | Value |
+---------------+-------+ | Qcache_hits | 3 | 

還是等於3，說明上一條sql是沒有直接從快取中直接得到的

+---------------+-------+ 1 row in set (0.00 sec)
mysql> select count(*) from animals; +----------+
| count(*) | +----------+ | 7 | +----------+
1 row in set (0.00 sec) mysql> SHOW STATUS LIKE 'Qcache_hits';
+---------------+-------+ | Variable_name | Value | +---------------+-------+
| Qcache_hits | 4 | +---------------+-------+ 1 row in set (0.00 sec)