DynamoDB query Partition Key with functions

Question

Hello,

Is it possible to query DynamoDB table on its Partition Key with a function, like in the below example, or do I need an index ?

```
QuerySpec spec = new QuerySpec()
    			.withKeyConditionExpression("begins_with(PicturePK, :v_prefix) ")
    			.withValueMap(new ValueMap() 
    			         .withString(":v_prefix", prefix));
```
Thank you,  
Mihai ADAM

Answer

As Jason states, you cannot use a function on the partition key. But you can add a GSI which can help your achieve the use-case. [This blog post](https://aws.amazon.com/blogs/database/effective-data-sorting-with-amazon-dynamodb/) outlines how you can achieve that.

GSI data:

| PK | PicturePK | Data |
| --- | --- | --- |
| 1 | 123 | Data |
| 1 | 321 | Data |
| 1 | 355 | Data |

```
QuerySpec spec = new QuerySpec()
    			.withKeyConditionExpression("PK = :pk AND begins_with(PicturePK, :v_prefix) ")
    			.withValueMap(new ValueMap() 
    			         .withString(":v_prefix", prefix)
                                 .withNumber(":pk", "1"));
```

Answer

With a query the partition key must be specified exactly. Sort keys can use begins_with.

DynamoDB query Partition Key with functions

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