Dynamodb V4: Table Scan Count Operation not possible with FilterExpression any more

[wirmar]

Describe the bug

With a Table table, when calling table.Scan(scanConfig).Count with a scanConfig that contains only a FilterExpression, the SDK throws the error:

Amazon.DynamoDBv2.AmazonDynamoDBException: Can not use both expression and non-expression parameters in the same request: Non-expression parameters: {ScanFilter} Expression parameters: {FilterExpression} ---> Amazon.Runtime.Internal.HttpErrorResponseException: Exception of type 'Amazon.Runtime.Internal.HttpErrorResponseException' was thrown.

With the AWSSDK v3 (previously using <PackageVersion Include="AWSSDK.DynamoDBv2" Version="3.7.5.20" />) this was possible without getting the error. The only difference in our code is creating the Table via TableBuilder instead of Table.LoadTable.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

The count is returned.

Current Behavior

An exception is thrown:

Amazon.DynamoDBv2.AmazonDynamoDBException: Can not use both expression and non-expression parameters in the same request: Non-expression parameters: {ScanFilter} Expression parameters: {FilterExpression} ---> Amazon.Runtime.Internal.HttpErrorResponseException: Exception of type 'Amazon.Runtime.Internal.HttpErrorResponseException' was thrown.

Reproduction Steps

        using var client = new AmazonDynamoDBClient(region);
        var config = new TableConfig(tableName)
        {
            Conversion = DynamoDBEntryConversion.V2
        };

        var tableBuilder = new TableBuilder(client, config);
        tableBuilder.AddHashKey(hashKey, DynamoDBEntryType.String);
        var table = tableBuilder.Build();
        var scanConfig = new ScanOperationConfig();
        scanConfig.FilterExpression = new Expression
            {
                ExpressionStatement = "Views >= :num",
                ExpressionAttributeValues = new Dictionary<string, DynamoDBEntry>
                {
                    {":num", new Primitive("10", true)}
                }
            };
        var count =table.Scan(scanConfig).Count;

Possible Solution

No response

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

AWSSDK.DynamoDBv2 4.0.12.1

Targeted .NET Platform

.NET 10

Operating System and version

AmazonLinux

[dscpinheiro]

I had to change your reproduction code a bit (with your example I got Invalid FilterExpression: Attribute name is a reserved keyword; reserved keyword: Views even in V3), but I was able to reproduce with:

var scanConfig = new ScanOperationConfig
{
    FilterExpression = new Expression
    {
        ExpressionStatement = "#V >= :num",
        ExpressionAttributeNames = new Dictionary<string, string>
        {
            { "#V", "Views" }
        },
        ExpressionAttributeValues = new Dictionary<string, DynamoDBEntry>
        {
            { ":num", new Primitive("10", true) }
        }
    }
};

V4 is sending this request:

{
    "ConsistentRead": false,
    "ExpressionAttributeNames": {
        "#V": "Views"
    },
    "ExpressionAttributeValues": {
        ":num": {
            "N": "10"
        }
    },
    "FilterExpression": "#V \u003E= :num",
    "ScanFilter": {},
    "Select": "COUNT",
    "TableName": "TestTable"
}

While V3 sends this instead (note there's no ScanFilter):

{
    "ConsistentRead": false,
    "ExpressionAttributeNames": {
        "#V": "Views"
    },
    "ExpressionAttributeValues": {
        ":num": {
            "N": "10"
        }
    },
    "FilterExpression": "#V >= :num",
    "Select": "COUNT",
    "TableName": "TestTable"
}

We're taking a look, but for a workaround at the moment you can set AWSConfigs.InitializeCollections = true before creating the AmazonDynamoDBClient (I tested that the scan request did succeed in V4, matching the V3 behavior).

[dscpinheiro]

The fix for this bug was included in https://github.com/aws/aws-sdk-net/releases/tag/4.0.196.0

Thanks again for reporting, please let us know if you run into more issues with DynamoDB in V4.

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