My scan function :
var tableName = 'faasos_orders',filterExp = 'status = :delivered OR status = :void OR status = :bad',projectionValues = '',expressionAttr = {}; expressionAttr[":delivered"] = "delivered";expressionAttr[":bad"] = "bad";expressionAttr[":void"] = "void"; limit = 10;dynamoConnector.getItemUsingScan(tableName, filterExp, projectionValues, expressionAttr, function (err, data) { ...........} Error on running :
{ [ValidationException: Invalid FilterExpression: Attribute name is a reserved keyword; reserved keyword: status]message: 'Invalid FilterExpression: Attribute name is a reserved keyword; reserved keyword: status',code: 'ValidationException',time: Mon Apr 18 2016 21:57:30 GMT+0530 (IST),requestId: 'AV6QFHM7SPQT1QR3D4OO81ED4FVV4KQNSO5AEMVJF66Q9ASUAAJG',statusCode: 400,retryable: false,retryDelay: 0 }Now I do get the point I am trying to use a reserved keyword in the filterExpression which is illegal. But if I run the same function through aws gui it returns data beautifully (check image for details): Scan function on status through gui
So the question is how do I add the filter expression through node without having to change the key name ???
Best Answer
Solved :
There are two parameters taken by aws-sdk :
Expression Attribute Name
Expression Attribute Value
both provide the functionality of replacing placeholders used in the attributes list.Here by Attributes it is a bit ambiguous, where I got confused.The wizards over at aws mean both the key and value when they use the term attribute.
So in a case where you want to use a reserved key word as a key attribute use the Expression Attribute Name parameter with #(pound) to denote the placeholder.
Similarly where you want to use placeholders for value attribute use the Expression Attribute Value parameter with :(colon) to denote the placeholder.
So finally my code (working) looks like this :
var param = {TableName: "faasos_orders",FilterExpression: "#order_status = :delivered OR #order_status = :void OR #order_status = :bad",ExpressionAttributeValues: {":delivered": "delivered",":void": "void",":bad": "bad"},ExpressionAttributeNames: {"#order_status": "status"}}; dynamodb.scan(param, function (err, data) {....});:status is a placeholder in your expression that you aren't providing a value for. See how you are providing values for your other placeholders here:
expressionAttr[":delivered"] = "delivered";expressionAttr[":bad"] = "bad";expressionAttr[":void"] = "void"You need to do the same for the :status placeholder. I don't see anything about a reserved word in the error message, so I'm not sure why you think that's the cause of the error. The error very specifically states that you aren't providing a value for the :status placeholder.