AWS DynamoDB - combining multiple query filters on a single non-key attribute in java

Question

Earlier this year Amazon announced support of query filters on non-key attributes.

Can conditions be combined on a single attribute value? For example, in this scenario I would like to retrieve all items which do not match a certain list of values in a single 'non-key' column.

Their documentation states that each condition can only hold one attribute value for comparisons like NOT_EQUALS or BEGINS_WITH . The following therefore does not work:

HashMap<String, Condition> queryFilter = new HashMap<String, Condition>();

List<AttributeValue> AttributeValues = new ArrayList<AttributeValue>();
AttributeValues.add(new AttributeValue().withS("someValue1"));
AttributeValues.add(new AttributeValue().withS("someValue2"));

Condition attributeCondition = new Condition()
    .withComparisonOperator(ComparisonOperator.NE)
    .withAttributeValueList(AttributeValues);

queryFilter.put("COLUMN_1", attributeCondition);

DynamoDBQueryExpression<Item> queryExpression = new DynamoDBQueryExpression<Item>()
    .withHashKeyValues(itemKey)
    .withQueryFilter(queryFilter)
    .withLimit(pPageSize);

It looks like only the IN comparison operator can hold a list of attribute values. Ideally these conditions should be chainable? Since the query filter is a hash map we cannot put multiple conditions on the same column (I've tried):

Condition c1 = new Condition()
    .withAttributeValueList(new AttributeValue().withS("someValue1"))
    .withComparisonOperator(ComparisonOperator.NE);

Condition c2 = new Condition()
    .withAttributeValueList(new AttributeValue().withS("someValue2"))
    .withComparisonOperator(ComparisonOperator.NE);

DynamoDBQueryExpression<Item> queryExpression = new DynamoDBQueryExpression<Item>()
    .withHashKeyValues(itemKey)
    .withConditionalOperator(ConditionalOperator.AND)
    .withQueryFilterEntry("COLUMN_1", c1)
    .withQueryFilterEntry("COLUMN_1", c2)
    .withLimit(pPageSize);

Any help or clarification would be greatly appreciated!

Thanks

Answer 1

So turns out this is made possible by adding a FilterExpression to the query (introduced recently in this blog post )

I had seen this in the DynamoDB documentation but hadn't upgraded to the latest AWS Java SDK :(

Using my above example this would look like:

Map<String, AttributeValue> expressionAttributeValues = new HashMap<String, AttributeValue>();
expressionAttributeValues.put(":val1", new AttributeValue().withS("someValue1"));
expressionAttributeValues.put(":val2", new AttributeValue().withS("someValue2"));

DynamoDBQueryExpression<Item> queryExpression = new DynamoDBQueryExpression<Item>()
    .withHashKeyValues(itemKey)
    .withFilterExpression("COLUMN_1 <> :val1 AND COLUMN_1 <> :val2")
    .withExpressionAttributeValues(expressionAttributeValues)
    .withLimit(pPageSize);

Thanks AWS Support!