Can I scan the highest range key value for each item in the table?

php Xiaobian Banana is here to answer a common question for everyone: "Can I scan the highest range key value of each item in the table?" Indeed, in some cases, You can get the highest range key value by scanning the items in the table. However, this depends on the database type and table structure you use. Some databases provide built-in functions or commands to obtain the maximum key value, while other databases require custom methods to achieve this. Regardless, we recommend that you carefully study the documentation of the database you are using before writing code and look for the relevant functions or methods to obtain the highest range key value.

Question content

Question: I want to get all items with the highest range key.

Example:

id Version 标题> Test 1 3 Test 1 4 Test 2 2 Test 2 3 表>

I expect query:

id Version 标题> Test 1 4 Test 2 3 表>

My table looks like this:

id string -> hash key 
version number -> range key

I'm using guregu and I'm scanning all results for the highest version number.

var results []map[string]interface{}
err := d.table.Scan().All(&results)

What is the best practice to find the item with the highest sort key?

Workaround

If you change the data model slightly and have a record in it (such as V0 in the image below), you can index sparseLatest value allows you to get the latest versions of all projects easily and efficiently.

Another method is to scan and then query, which is extremely inefficient. So if it's a frequent lookup pattern, then indexing is best.

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