DYNDB019: Potential key collision

Field	Value
Code	DYNDB019
Severity	Warning

Message

Key format '{0}' on property '{1}' may produce non-unique keys for different values

Description

Key formats should ensure uniqueness to avoid DynamoDB key collisions. If a key format can produce the same key string for different input values, items may overwrite each other silently in DynamoDB.

Example

The following code triggers this diagnostic:

[DynamoDbTable("Events")]
public partial class Event
{
    [PartitionKey]
    [DynamoDbAttribute("pk")]
    [Computed("Category", "SubCategory", Separator = "")]
    public string Pk { get; set; } = string.Empty;

    [Extracted("Pk", 0)]
    public string Category { get; set; } = string.Empty;

    [Extracted("Pk", 1)]
    public string SubCategory { get; set; } = string.Empty;
}

Fix

The corrected version:

[DynamoDbTable("Events")]
public partial class Event
{
    [PartitionKey]
    [DynamoDbAttribute("pk")]
    [Computed("Category", "SubCategory", Separator = "#")]
    public string Pk { get; set; } = string.Empty;

    [Extracted("Pk", 0)]
    public string Category { get; set; } = string.Empty;

    [Extracted("Pk", 1)]
    public string SubCategory { get; set; } = string.Empty;
}