在 cfquery 中使用 cachedwithin 属性

发布于 2024-09-05 10:33:52 字数 202 浏览 7 评论 0原文

当您在 cfquery 中使用 cachedwithin 属性时，它如何将查询存储在内存中。它是否仅按您分配给查询的名称存储它？例如，如果在我的索引页面上我缓存一个查询一个小时并将其命名为 getPeople，则不同页面（或同一页面）上具有相同名称的查询将使用缓存的结果，或者它是否使用一些更好的逻辑判断是否是同一个查询？

另外，如果查询中有变量，缓存是否会考虑该变量的值？

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软的没边 2024-09-12 10:33:53

它不仅仅是名称——它是您正在运行的确切查询。

<cfquery name="getPeople" cachedwithin=".5" ...>
select name from employee order by name
</cfquery>

如果您在应用程序中的其他任何地方调用相同的查询，并且在第一次查询后的半天内，您将获得缓存的版本。但这些将访问数据库以获取新数据：

<!--- Different name, same SQL: A new cached query --->
<cfquery name="getEmployees" cachedwithin=".5" ...>
select name from employee order by name
</cfquery>

<!--- Different SQL, same name: Redefining the cached query --->
<!--- Note: As pointed out in comments, it's not really overwriting the old query
      of the same name, but making a new one in the cache. The first one by the
      same name is still in the cache, waiting for eviction. --->
<cfquery name="getPeople" cachedwithin=".5" ...>
select name from employee order by name desc
</cfquery>

是的，它确实考虑了一个变量。如果您使用cfqueryparam——您应该这样做——您的数据库将缓存查询计划，但即使使用cachedwithin，每个查询从查询缓存的角度来看，更改的参数将被视为不同的参数。请注意，这意味着如果您在使用不同参数运行多次的查询上使用 cachedwithin，则缓存命中率较低的查询会淹没您的查询缓存。

It's not only the name -- it's the exact query you're running.

<cfquery name="getPeople" cachedwithin=".5" ...>
select name from employee order by name
</cfquery>

If you invoke this same query anywhere else in your app, you'll get the cached version if it's within half a day of the first query. But these will hit the database for fresh data:

<!--- Different name, same SQL: A new cached query --->
<cfquery name="getEmployees" cachedwithin=".5" ...>
select name from employee order by name
</cfquery>

<!--- Different SQL, same name: Redefining the cached query --->
<!--- Note: As pointed out in comments, it's not really overwriting the old query
      of the same name, but making a new one in the cache. The first one by the
      same name is still in the cache, waiting for eviction. --->
<cfquery name="getPeople" cachedwithin=".5" ...>
select name from employee order by name desc
</cfquery>

And yes, it does take a variable into account. If you use cfqueryparam -- which you should be doing -- your database will cache the query plan, but even using cachedwithin, each query with a changed parameter will be treated as different from a query caching perspective. Note that this means if you use cachedwithin on a query that runs many times with different parameters, you'll be flooding your query cache with queries that have low cache hit rates.

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