I am trying to create a silent auction site. My Lambda function should update an item under the condition that the submitted bid > current high bid. However, the condition does not seem to be applying; the update occurs even if the submitted bid is less than the current high bid.
Please help me identify what I'm doing wrong:
##My DynamoDB table looks like this:##
Table name: SilentAuction2
Primary partition key: ItemID (String)
other attributes:
CurrentHighBid (Number)
HighestBidder (String)
Notes (String)
BidHistoryBids (List)
BidHistoryPPL (List)
My condition, as stated above, is that the incoming event.NewBid is greater than the CurrentHighBid. Here is the Lambda code in Node.JS:
const AWS = require('aws-sdk');
const docClient = new AWS.DynamoDB.DocumentClient({region: 'us-east-1'});
exports.handler = function index(event, context, callback) {
var table = "SilentAuction2";
var ItemID = event.ItemID;
var NewBid = event.NewBid;
var NewBidder = event.NewBidder;
var Notes = event.Notes;
var params = {
TableName:table,
Key:{
"ItemID": ItemID
},
//update and append values
UpdateExpression: "SET #BidList = list_append(#BidList, :hb),
#PplList = list_append(#PplList, :hp),
CurrentHighBid =:c,
HighestBidder=:h,
Notes=:n",
//condition on which to update if true
ConditionalExpression: " :c > CurrentHighBid",
ExpressionAttributeNames: {
"#BidList" : "BidHistoryBids",
"#PplList" : "BidHistoryPPL"
},
ExpressionAttributeValues:{
":hb":[NewBid],
":hp":[NewBidder],
":n":Notes,
":c":NewBid,
":h":NewBidder
},
ReturnValues:"UPDATED_NEW"
};
docClient.update(params, function(err, data){
if(err){
callback(err, null);
}else{
callback(null, data);
}
});
};
This links were helpful in researching ConditionalExpression within DynamoDB:
https://egkatzioura.com/2016/08/09/update-dynamodb-items-with-node-js/
http://docs.aws.amazon.com/amazondynamodb/latest/gettingstartedguide/GettingStarted.NodeJs.03.html#GettingStarted.NodeJs.03.05
Related
I am using nodejs aws-sdk/clients/dynamodb library with dynamodb. I need to update an item in the table. Below is the sample code to update an item:
params = {
TableName:table,
Key:{
"year": year,
"title": title
},
UpdateExpression: "set info.rating = info.rating + :val",
ExpressionAttributeValues:{
":val": 1
},
ReturnValues:"UPDATED_NEW"
};
I will have to specify each attribute in info in UpdateExpression. My info object is very big and I am looking for an easier way to do that. Is there a build-in method to support update an object to dynamodb item? something like:
params = {
TableName:table,
Key:{
"year": year,
"title": title
},
Item: info
};
The answer given by E.J. Brennan is great for cases where it's ok to replace the entire item. DocumentClient eases the hassle of dealing with DynamoDB attribute types, but the example given uses the put method. According to the docs put passes through to putItem which
Creates a new item, or replaces an old item with a new item
That means that it's not going to help with partial updates to existing items where you don't already have the full record (and can get away with a full replacement). For partial updates you have to use updateItem, or it's DocumentClient counterpart, update.
The AWS labs has published a utility to help with constructing update expressions to use with updateItem. Since I generally prefer to use DocumentClient, I unmarshall values with the utility function provided by DynamoDB's Converter (yes, I know it's a bit a back and forth, but it makes testing easier).
const AWS = require('aws-sdk');
const db = new AWS.DynamoDB.DocumentClient();
const { UpdateExpression, ExpressionAttributes } = require('#aws/dynamodb-expressions');
const { unmarshall } = AWS.DynamoDB.Converter;
const updateExpressionProps = ({ category, classification }) => {
attributes = new ExpressionAttributes();
expression = new UpdateExpression();
expression.set('category', category);
expression.set('classification', classification);
return {
UpdateExpression: expression.serialize(attributes),
ExpressionAttributeNames: attributes.names,
ExpressionAttributeValues: unmarshall(attributes.values),
};
};
const updateRequest = async ({ id, subject, category, classification }) =>
await db
.update({
TableName: 'table-name',
Key: {
id,
subject,
},
...updateExpressionProps({ category, classification }),
})
.promise();
This bit of code only updates the category and classification attributes on the record identified with id and subject without the hassle of manually building a correct UpdateExpression string. This example could easily be generalized into something reusable throughout your project.
I wrote the following utility method to convert a given object to UpdateExpression (SET only), ExpressionAttributeNames, and ExpressionAttributeValues.
const convertToCompositePathObj = (obj: Record<any, any>) => {
const res: Record<string, string | number | []> = {};
const getPropertyPath = (obj: Record<any, any>, current = "") => {
for (let key in obj) {
const value = obj[key];
const newKey = current ? [current, key].join(".") : key;
if (value && typeof value === "object" && !Array.isArray(value)) {
getPropertyPath(value, newKey);
} else res[newKey] = value;
}
};
getPropertyPath(sampleObject);
return res;
};
const generateDynamoDbUpdateExpression = (obj: Record<any, any>) => {
const compositePathObj = convertToCompositePathObj(sampleObject);
let counter = 0;
let updateExpression = "SET ";
const expressionAttNamesMap: any = {};
const expressionAttValuesMap: any = {};
for (let k in compositePathObj) {
const newUpdateExpression = k
.split(".")
.map((item) => {
const attName = `#${item}`;
if (!expressionAttNamesMap[attName]) {
expressionAttNamesMap[attName] = item;
}
return attName;
})
.join(".")
.concat(`= :${counter} AND `);
expressionAttValuesMap[`:${counter}`] = compositePathObj[k];
counter += 1;
updateExpression += newUpdateExpression;
}
updateExpression = updateExpression.substring(0, updateExpression.length - 5);
return {
UpdateExpression: updateExpression,
ExpressionAttributeNames: expressionAttNamesMap,
ExpressionAttributeValues: expressionAttValuesMap
};
};
// example usage:
const sampleObject = {
name: {
first: "John",
last: "Doe"
},
address: {
line1: "123 test st.",
line2: "Apt 123",
city: "Los Angeless",
state: "CA",
zip: 92763
},
phone: 8675768475
};
console.log(generateDynamoDbUpdateExpression(sampleObject));
/**
*****OUTPUT*****
{
UpdateExpression: "SET #name.#first= :0 AND #name.#last= :1 AND #address.#line1= :2 AND #address.#line2= :3 AND #address.#city= :4 AND #address.#state= :5 AND #address.#zip= :6 AND #phone= :7",
ExpressionAttributeNames:{
#name: "name"
#first: "first"
#last: "last"
#address: "address"
#line1: "line1"
#line2: "line2"
#city: "city"
#state: "state"
#zip: "zip"
#phone: "phone"
},
ExpressionAttributeValues:{
:0: "John"
:1: "Doe"
:2: "123 test st."
:3: "Apt 123"
:4: "Los Angeless"
:5: "CA"
:6: 92763
:7: 8675768475
}
}
**/
PS: I wrote this in a hurry so please excuse the formatting and any types.
https://codesandbox.io/s/aws-dynamic-update-expression-set-33tye7?file=/src/index.ts
You could use the Document Client:
Version 2.2.0 of the AWS SDK for JavaScript introduces support for the
document client abstraction in the AWS.DynamoDB namespace. The
document client abstraction makes it easier to read and write data to
Amazon DynamoDB with the AWS SDK for JavaScript. Now you can use
native JavaScript objects without annotating them as AttributeValue
types.
For example:
var docClient = new AWS.DynamoDB.DocumentClient({region: 'us-west-2'});
var params = {
Item: {
hashkey: 'key',
boolAttr: true,
listAttr: [1, 'baz', true]
mapAttr: {
foo: 'bar'
}
},
TableName: 'table'
};
docClient.put(params, function(err, data){
if (err) console.log(err);
else console.log(data);
});
https://aws.amazon.com/blogs/developer/announcing-the-amazon-dynamodb-document-client-in-the-aws-sdk-for-javascript/
I'm trying to return only values where john is found from a DynamoDB database.
I'm able to return values where it contains name: john from a mapped list, however the problem am having is that it appears to also be returning other values as well.
Running select: 'count' returns 1 match which is correct but it doesn't return anything when used.
I'm assuming that count just returns a number and not a specific select where john is matched.
I'm writing this in NodeJS; am hoping someone can help me figure this out.
I know that the value I only want shown are json elements where name: john, anything else I want omitted from being shown.
Here's my result as of right now:
{
"Department": [
{
"employees": [
{
"name": "john"
},
{
"name": "sally"
}
]
}
],
"Count": 1
}
My code:
const AWS = require('aws-sdk'); // eslint-disable-line import/no-extraneous-dependencies
const dc = new AWS.DynamoDB.DocumentClient();
exports.handler = async (event, context, callback) => {
// Construct the params for filtering data through dynamodb
const params = {
FilterExpression: "contains(#department, :employees)",
ExpressionAttributeNames: {
"#department": "employees",
},
ExpressionAttributeValues: {
":employees": {
"name":"john"
}
},
ProjectionExpression: "#department",
TableName: 'mytable',
//Select: 'COUNT'
};
const resultDC = await dc.scan(params).promise();
var items = resultDC.Items;
var count = resultDC.Count;
var returned_list = {
'Department' : items,
'Count' : count,
};
// create a response
const response = {
statusCode: 200,
body: JSON.stringify(returned_list),
};
callback(null, response);
};
I suggest you to use a Local Secondary Index.
Take a look here.
I am trying to retrieve values from DynamoDB when passing the primary partition key as the parameters in the URL.
I have a table with two columns:
movie id
movie name.
I want to be able to pass the movie id in the URL and to get the correspondent movie as a result. I have already created following lambda function and connected it to an API and DynamoDB.
I am not able to figure out the piece of code to use in order to retrieve the movie name when passing movie id as a parameter
Here is my code so far:
console.log('Loading function');
const AWS = require('aws-sdk');
const docClient = new AWS.DynamoDB.DocumentClient({region: 'us-east-2'});
exports.handler = function(event, context,callback) {
var params = {
TableName: 'movie',
Key: {
"movieID": 5,
}
}
docClient.get(params, function(err, data){
if(err){
callback(err,null);
}else{
callback(null, data);
}
})
};
Try
var params = {
TableName: 'movie',
Key: {
"movieID": 5,
},
AttributesToGet= [
"movie_name"
],
ProjectionExpression: 'movie_name"
}
https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html
AttributesToGet is a legacy field as per documentation and ProjectionExpression should be used instead.
I have a table with an attribute with name id and of type HASH. I want to get all items from a array of id's.
{
TableName: `MyTable`,
FilterExpression: 'id IN (:id)',
ExpressionAttributeValues: { ':id': ids },
};
What should I do to get all items by my ids?
You can also use DocumentClient and batchGet.
const AWS = require('aws-sdk');
const documentClient = new AWS.DynamoDB.DocumentClient();
let queryParams = {RequestItems: {}};
queryParams.RequestItems['tableName'] = {
Keys: [{'id': 'Value1'}, {'id': 'value2'}],
ProjectionExpression: 'id' //define other fileds that you have Ex: 'id,name'
};
documentClient.batchGet(queryParams, function (err, data) {
if (err) {
console.log('failure:getItemByBatch data from Dynamo error', err);
} else {
console.log('success:getItemByBatch data from Dynamo data');
console.log(data)
}
});
Please use BatchGetItem API to get multiple values from DynamoDB table.
BatchGetItem
Example:-
var dynamodb = new AWS.DynamoDB({maxRetries: 5, retryDelayOptions: {base: 300} });
var table = "Movies";
var year_val = 2015;
var title = "The Big New Movie";
var params = {
"RequestItems" : {
"Movies" : {
"Keys" : [ {
"yearkey" : {N : "2016"},
"title" : {S : "The Big New Movie 1"}
} ]
}
},
"ReturnConsumedCapacity" : "TOTAL"
};
dynamodb.batchGetItem(params, function(err, data) {
if (err) {
console.error("Unable to get item. Error JSON:", JSON.stringify(err,
null, 2));
} else {
console.log("Movie data:", JSON.stringify(data, null, 2));
}
});
Its in C#, below code is to get all items by an array of ids from a dynamodb table having different guid's using BatchGet or CreateBatchGet
string tablename = "AnyTableName"; //table whose data you want to fetch
var BatchRead = ABCContext.Context.CreateBatchGet<ABCTable>(
new DynamoDBOperationConfig
{
OverrideTableName = tablename;
});
foreach(string Id in IdList) // in case you are taking string from input
{
Guid objGuid = Guid.Parse(Id); //parsing string to guid
BatchRead.AddKey(objGuid);
}
await BatchRead.ExecuteAsync();
var result = BatchRead.Results;
// ABCTable is the table modal which is used to create in dynamodb & data you want to fetch
I am quite new to work with DynamoDB. I would like to query DynamoDB database for a specific column value and get the data that matches that specific column value using NodeJS sdk
In this case, the DynamoDB is already deployed.
Please suggest how to implement this workflow using Node JS.
most important thing is to create a JSON object containing
the parameters needed to query the table, which in this example includes the table name, the
ExpressionAttributeValues needed by the query, a KeyConditionExpression that uses those
values to define which items the query returns, and the names of attribute values to return for each
item. Call the query method of the DynamoDB service object.
here is an example to query dynamodb with nodejs sdk
// Load the AWS SDK for Node.js
var AWS = require('aws-sdk');
// Set the region
AWS.config.update({region: 'REGION'});
// Create DynamoDB service object
var b = new AWS.DynamoDB({apiVersion: '2012-08-10'});
var params = {
ExpressionAttributeValues: {
':s': {N: '2'},
':e' : {N: '09'},
':topic' : {S: 'PHRASE'}
},
KeyConditionExpression: 'Season = :s and Episode > :e',
ProjectionExpression: 'Episode, Title, Subtitle',
FilterExpression: 'contains (Subtitle, :topic)',
TableName: 'EPISODES_TABLE'
};
b.query(params, function(err, data) {
if (err) {
console.log("Error", err);
} else {
data.Items.forEach(function(element, index, array) {
console.log(element.Title.S + " (" + element.Subtitle.S + ")");
});
}
});