MySQL查询
以下的文章主要介绍的是MySQL 查询缓存的实际应用代码以及查看MySQL 查询缓存的大小 ，碎片整理，清除缓存以及监视MySQL 查询缓存性能的相关内容的描述，以下就是具体内容的描述，希望在你今后的学习中会有所帮助。
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> select @@query_cache_type; </span></span> </li> <li><span>+--------------------+ </span></li> <li class="alt"><span>| @@query_cache_type | </span></li> <li><span>+--------------------+ </span></li> <li class="alt"><span>| ON | </span></li> <li><span>+--------------------+ </span></li> <li class="alt">MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> set </span><span class="attribute"><font color="#ff0000">query_cache_type</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">off</font></span><span>; </span> </li> <li>MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> set </span><span class="attribute"><font color="#ff0000">query_cache_type</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">on</font></span><span>; </span> </li> <li class="alt">MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> </span> </li> <li>MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> select sql_cache id, title, body from article; </span> </li> <li class="alt">MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> select sql_no_cache id, title, body from article; </span> </li> <li>MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> show variables like 'have_query_cache'; </span> </li> <li class="alt"><span>+------------------+-------+ </span></li> <li><span>| Variable_name | Value | </span></li> <li class="alt"><span>+------------------+-------+ </span></li> <li><span>| have_query_cache | YES | </span></li> <li class="alt"><span>+------------------+-------+ </span></li> <li><span>1 row in set (0.00 sec) </span></li> </ol>
查看MySQL 查询缓存的大小
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> select @@global.query_cache_size; </span></span> </li> <li><span>+---------------------------+ </span></li> <li class="alt"><span>| @@global.query_cache_size | </span></li> <li><span>+---------------------------+ </span></li> <li class="alt"><span>| 16777216 | </span></li> <li><span>+---------------------------+ </span></li> <li class="alt"><span>1 row in set (0.00 sec) </span></li> <li>MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> select @@query_cache_size; </span> </li> <li class="alt"><span>+--------------------+ </span></li> <li><span>| @@query_cache_size | </span></li> <li class="alt"><span>+--------------------+ </span></li> <li><span>| 16777216 | </span></li> <li class="alt"><span>+--------------------+ </span></li> <li><span>1 row in set (0.00 sec) </span></li> </ol>
查看最大缓存结果，如果结果集大于该数，不缓存。
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> select @@global.query_cache_limit; </span></span> </li> <li><span>+----------------------------+ </span></li> <li class="alt"><span>| @@global.query_cache_limit | </span></li> <li><span>+----------------------------+ </span></li> <li class="alt"><span>| 1048576 | </span></li> <li><span>+----------------------------+ </span></li> <li class="alt"><span>1 row in set (0.00 sec) </span></li> </ol>
碎片整理
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> flush query cache </span></span> </li> <li> <span>-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> ; </span> </li> <li class="alt"><span>Query OK, 0 rows affected (0.00 sec) </span></li> </ol>
清除缓存
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> reset query cache </span></span> </li> <li> <span>-</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> ; </span> </li> <li class="alt"><span>Query OK, 0 rows affected (0.00 sec) </span></li> </ol>
监视MySQL 查询缓存性能：
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> flush tables; </span></span> </li> <li><span>Query OK, 0 rows affected (0.04 sec) </span></li> <li class="alt">MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> show status like 'qcache%'; </span> </li> <li><span>+-------------------------+----------+ </span></li> <li class="alt"><span>| Variable_name | Value | </span></li> <li><span>+-------------------------+----------+ </span></li> <li class="alt"><span>| Qcache_free_blocks | 1 | </span></li> <li><span>| Qcache_free_memory | 16768408 | </span></li> <li class="alt"><span>| Qcache_hits | 6 | </span></li> <li><span>| Qcache_inserts | 36 | </span></li> <li class="alt"><span>| Qcache_lowmem_prunes | 0 | </span></li> <li><span>| Qcache_not_cached | 86 | </span></li> <li class="alt"><span>| Qcache_queries_in_cache | 0 | </span></li> <li><span>| Qcache_total_blocks | 1 | </span></li> <li class="alt"><span>+-------------------------+----------+ </span></li> <li><span>8 rows in set (0.06 sec) </span></li> </ol>
看看当前缓存中有多少条信息：
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag"><strong><font color="#006699">></font></strong></span><span> show status like 'qcache_q%'; </span></span> </li> <li><span>+-------------------------+-------+ </span></li> <li class="alt"><span>| Variable_name | Value | </span></li> <li><span>+-------------------------+-------+ </span></li> <li class="alt"><span>| Qcache_queries_in_cache | 0 | </span></li> <li><span>+-------------------------+-------+ </span></li> <li class="alt"><span>1 row in set (0.00 sec) </span></li> <li>MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> select sql_cache id, title, body from article; </span> </li> <li class="alt">MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> show status like 'qcache_q%'; </span> </li> <li><span>+-------------------------+-------+ </span></li> <li class="alt"><span>| Variable_name | Value | </span></li> <li><span>+-------------------------+-------+ </span></li> <li class="alt"><span>| Qcache_queries_in_cache | 1 | </span></li> <li><span>+-------------------------+-------+ </span></li> <li class="alt"><span>1 row in set (0.00 sec) </span></li> <li>MySQL<span class="tag"><strong><font color="#006699">></font></strong></span><span> show status like 'qcache_f%'; </span> </li> <li class="alt"><span>+--------------------+----------+ </span></li> <li><span>| Variable_name | Value | </span></li> <li class="alt"><span>+--------------------+----------+ </span></li> <li><span>| Qcache_free_blocks | 1 | </span></li> <li class="alt"><span>| Qcache_free_memory | 16766728 | </span></li> <li><span>+--------------------+----------+ </span></li> <li class="alt"><span>2 rows in set (0.00 sec) </span></li> </ol>
以上的相关内容就是对MySQL 查询缓存的介绍，望你能有所收获。
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