涉及嵌套属性时如何减少DynamoDB GSI项目大小
DynamoDB将查询响应大小限制为1MB，因此为了最大化每个查询的项目数量，我想减少单个项目的大小。由于我通过GSI查询，因此一种自然方法是减少投影的属性数量。问题在于，我需要的一些属性是嵌套属性，而不是顶级属性。包括顶级属性在内将使GSI中的项目条目太大。
我知道没有办法在GSI中投射嵌套属性。是否有工作可以减少项目大小的工作，同时允许我在单个查询中访问嵌套属性？
DynamoDB limits query response size to 1MB, so to maximize the number of items returned per query, I would like to reduce the size of an individual item. Since I query by GSI, one natural approach is to reduce the number of attributes projected. The problem is that a few of the attributes that I need is a nested attribute and not a top-level attribute. Including the top-level attribute will make the items entries in GSI too large.
I am aware there is no way to project a nested attribute in a GSI. Is there any work-around to reduce the item size while allowing me to access nested attribute within a single query?
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我想开始说您的第一个假设，DynamoDB
QUERY仅限于1MB，这是不正确的。确实，查询将在读取1MB数据后返回结果，但是您可以继续获取下一个结果 - 一种称为 paging 的过程。请参阅QUERY文档，清楚地说明了如何做。如果尽管如此，您仍然只想检索每个项目的部分而不是整个项目，这很容易做到 - 使用投影表达。如果您在
查询期间传递投影表达，它将仅返回所检索的项目的一部分。它甚至使您只能像您想要的那样返回一块嵌套属性。不过，请注意，即使您仅检索一小块大物品，您仍然会付款用于检索整个物品。这是GSI的好处，您不会使用
投射表达- 您不会获得更便宜的检索。另外，它不会帮助您进行最初的单页查询，因为1MB页面截止是在项目大小级别上发生的，而不是返回的数据长度级别。因此，您仍然需要实现分页，而不是假设一个页面总是足够的。I want to start by saying that your first assumption, that DynamoDB
Queryis limited to 1MB, is incorrect. Indeed,Querywill return results after having read 1MB of data, but you can continue fetching the next results - a process known as paging. Please refer to theQuerydocumentation where it is clearly explained how to do it.If, despite learning this, you still want to retrieve only pieces of each item and not the entire items, that's easy to do - using a ProjectionExpression. If you pass a
ProjectionExpressionduring aQuery, it will return only parts of the retrieved items. It even allows you to return only a piece of a nested attribute, exactly like you wanted.Be aware, though, that even if you only retrieve small pieces of large items, you will still pay for retrieving the entire item. That's a benefit of GSI you don't get by using
ProjectionExpression- you don't get cheaper retrieval. Also, it won't help you with the single-page query you began with, because the 1MB page cutoff happens at the item-size level, not the returned data length level. So you'll still need to implement paging and not assume that a single page is always enough.