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 th e 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 ???
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) {....});