// If you decide your primary key is just the partition key.
class PrimaryKey(partitionKey: String)
// and in thids case
getRow(somePartitionKey): Row
然而，在这种情况下，你可以决定你的主键是分区键+排序键:
// if you decide your primary key is partition key + sort key
class PrimaryKey(partitionKey: String, sortKey: String)
getRow(partitionKey, sortKey): Row
getMultipleRows(partitionKey): Row[]
所以底线是:
确定你的主键只是分区键?按分区键获取单行。
决定你的主键是分区键+排序键?
2.1通过(分区键，排序键)获取单行或通过(分区键)
获取行范围
无论哪种方式，你都可以通过主键获得一行，唯一的问题是你是否将主键定义为仅为分区键或分区键+排序键
构建模块是:
表格
项
KV属性。
将Item视为一行，KV Attribute视为该行中的单元格。
您可以通过主键获取一个项(一行)。
你可以通过指定(HashKey, RangeKeyQuery)来获取多个项目(多行)
只有当你决定你的PK由(HashKey, SortKey)组成时，你才能执行(2)。
更直观的是，它的复杂，我是这样看的:
+----------------------------------------------------------------------------------+
|Table |
|+------------------------------------------------------------------------------+ |
||Item | |
||+-----------+ +-----------+ +-----------+ +-----------+ | |
|||primaryKey | |kv attr | |kv attr ...| |kv attr ...| | |
||+-----------+ +-----------+ +-----------+ +-----------+ | |
|+------------------------------------------------------------------------------+ |
|+------------------------------------------------------------------------------+ |
||Item | |
||+-----------+ +-----------+ +-----------+ +-----------+ +-----------+ | |
|||primaryKey | |kv attr | |kv attr ...| |kv attr ...| |kv attr ...| | |
||+-----------+ +-----------+ +-----------+ +-----------+ +-----------+ | |
|+------------------------------------------------------------------------------+ |
| |
+----------------------------------------------------------------------------------+
+----------------------------------------------------------------------------------+
|1. Always get item by PrimaryKey |
|2. PK is (Hash,RangeKey), great get MULTIPLE Items by Hash, filter/sort by range |
|3. PK is HashKey: just get a SINGLE ITEM by hashKey |
| +--------------------------+|
| +---------------+ |getByPK => getBy(1 ||
| +-----------+ +>|(HashKey,Range)|--->|hashKey, > < or startWith ||
| +->|Composite |-+ +---------------+ |of rangeKeys) ||
| | +-----------+ +--------------------------+|
|+-----------+ | |
||PrimaryKey |-+ |
|+-----------+ | +--------------------------+|
| | +-----------+ +---------------+ |getByPK => get by specific||
| +->|HashType |-->|get one item |--->|hashKey ||
| +-----------+ +---------------+ | ||
| +--------------------------+|
+----------------------------------------------------------------------------------+
