Posted: 11/Jan/2024
Conditional operations are helpful in cases when you want a DynamoDB write operation (PutItem, UpdateItem or DeleteItem) to be executed based on a certain criteria. To do so, use a condition expression - it must evaluate to true in order for the operation to succeed.
Here is an example that demonstrates a conditional UpdateItem operation. It uses the attribute_not_exists function:
resp,err:=client.UpdateItem(context.Background(),&dynamodb.UpdateItemInput{TableName:aws.String(tableName),Key:map[string]types.AttributeValue{"email":&types.AttributeValueMemberS{Value:email},},UpdateExpression:aws.String("SET first_name = :fn"),ExpressionAttributeValues:map[string]types.AttributeValue{":fn":&types.AttributeValueMemberS{Value:firstName,},},ConditionExpression:aws.String("attribute_not_exists(account_locked)"),ReturnConsumedCapacity:types.ReturnConsumedCapacityTotal,})Recommended reading - ConditionExpressions
