looking for an answer to this question if possible, not looking for a refactoring advice or redesign, i just need to understand what else I am missing here :
I have an existing item in dynamodb:
{
"CartId": 321,
"UserId": usr555,
"CartItems": [
{
"ProductId":59999,
"Quantity": 1
},
{
"ProductId": 58888,
"Quantity": 2
}
]
}
in my code I want to insert another nested attribute into the array CartItems in the item above. i can't find a way of doing this without retrieving the entire item and then inserting, which could amount to KBs in size.
all I want to do is insert a single array element in an existing nested attribute without having to retrieve the item.
the language I am using is nodejs and the function is DynamoDB.put.
UpdateExpression attribute supports SET action and SET action supports list_append function. Since list_append function operands must be list, enclose the new value within a list as below.
response = dynamodb_client.update_item(TableName='your_table',
Key={'CartId':'321'},
UpdateExpression='SET CartItems = list_append(CartItems, :val1)',
ExpressionAttributeValues = {':val1':[{'ProductId':12345, 'Quantity': 100}]})
Hope this helps
Related
In DynamoDb, is it possible to do a conditional put and return the old item if there already was a matching item?
I would like something like the following to create the row if the user does not already exist, and if it does exist, I want it to return the old item (with whatever name was there before). I.e., insert item if new, else just read existing item.
await documentClient.put({
TableName: 'table',
Item: {
userId: 'user0',
name: 'smith',
},
ConditionExpression: 'attribute_not_exists(userId)',
});
Is this possible to do in one call?
Sort of.
If you use UpdateItem it will create or update the item. It only updates the fields that have changed however, so if your fields have not changed, then no update will be made. It will also create the item if you do not have it.
Using Conditional Items for this will return an ErrorCode if the condition fails ConditionalCheckFailedException - which would require an additional operation.
(I don't use the javascript SDK that much, more in python, so I'm not sure this is the correct version/page but here is some documentation:
https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#updateItem-property )
How can I get a collection where the query should be applicable to an array inside the document.
Document example: I would like to know how to query the document where the brands are fiat and seat
{
"name":"test 1",
"brands":[
{
"brand":{
"id":1,
"name":"Fiat",
"slug":"fiat",
"image":null,
"year_end":null,
"year_start":null
},
"released_at":"2018-10-26"
},
{
"brand":{
"id":2,
"name":"Seat",
"slug":"seat",
"image":null,
"year_end":null,
"year_start":null
},
"released_at":"2018-10-26"
},
{
"brand":{
"id":3,
"name":"Mercedes",
"slug":"mercedes",
"image":null,
"year_end":null,
"year_start":null
},
"released_at":"2018-10-26"
},
{
"brand":{
"id":4,
"name":"Yamaha",
"slug":"yamaha",
"image":null,
"year_end":null,
"year_start":null
},
"released_at":"2018-10-26"
}
]
}
I have tried something like:
.collection("motors")
.where("brands.slug", "array-contains-any", ["fiat", "seat"])
but this is not working I cannot figure out by the documentation how to get this.
When using the array-contains-any operator, you can check the values of your array against the value of a property of type String and not an array. There is currently no way you can use array-contains-any operator on an array. There are two options, one would be to create two separate fields and create two separate queries or, been only a document, you can get the entire document and filter the data on the client.
Edit:
What #FrankvanPuffelen has commented is correct, I made some research and I found that we can check against any type and even complex types, not just against strings, as mentioned before. The key to solving this issue is to match the entire object, meaning all properties of that object and not just a partial match, for example, one of three properties.
What you are trying to achieve is not working with your current database structure because your slug property exists in an object that is nested within the actual object that exists in your array. A possible solution might also be to duplicate some data and add only the desired values into an array and use the array-contains-any operator on this new creatded array.
I am trying to append to a string set (array of strings) column, which may or may not already exist, in a DynamoDB table. I referred to SO questions like this and this when writing my UpdateExpression.
My code looks like this.
const AWS = require('aws-sdk')
const dynamo = new AWS.DynamoDB.DocumentClient()
const updateParams = {
// The table definitely exists.
TableName: process.env.DYNAMO_TABLE_NAME,
Key: {
email: user.email
},
// The column may or may not exist, which is why I am combining list_append with if_not_exists.
UpdateExpression: 'SET #column = list_append(if_not_exists(#column, :empty_list), :vals)',
ExpressionAttributeNames: {
'#column': 'items'
},
ExpressionAttributeValues: {
':vals': ['test', 'test2'],
':empty_list': []
},
ReturnValues: 'UPDATED_NEW'
}
dynamo.update(updateParams).promise().catch((error) => {
console.log(`Error: ${error}`)
})
However, I am getting this error: ValidationException: An operand in the update expression has an incorrect data type. What am I doing incorrectly here?
[Update]
Thanks to Nadav Har'El's answer, I was able to make it work by amending the params to use the ADD operation instead of SET.
const updateParams = {
TableName: process.env.DYNAMO_TABLE_NAME,
Key: {
email: user.email
},
UpdateExpression: 'ADD items :vals',
ExpressionAttributeValues: {
':vals': dynamo.createSet(['test', 'test2'])
}
}
A list and a string set are not the same type - a string set can only hold strings while a list may hold any types (including nested lists and objects), element types don't need to be the same, and a list can hold also duplicate items. So if your original item is indeed as you said a string set, not a list, this explains why this operation cannot work.
To add items to a string set, use the ADD operation, not the SET operation. The parameter you will give to add should be a set (not a list, I don't know the magic js syntax to specify this, check your docs) with a bunch of elements. If the attribute already exists these elements will be added to it (dropping duplicates), and if the attribute doesn't already exit, it will be set to the set of these elements. See the documentation here: https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html#DDB-UpdateItem-request-UpdateExpression
I'm trying to use SCC to write some contracts before I rebuild the producer side (there are no existing tests!). The examples around lists and deeper data structures in the documents are a bit thin, so I want to understand if this is feasible, or perhaps I have to drop down to calling a command to make the right assertions.
I'm using the latest version v2.11
So -
Given:
An API that will return a list of objects in its payload. The length of the list will depending on the identity of the client, i.e. client A will get 3 items, client B will get 4 items. The identity of the client isn't of interest here.
When:
A client makes a GET request, passing a querystring parameter for item selection within the list of items
Then:
I want to write a contract that takes input from request and proves that the response contains a list of objects, and the item that matches the selector has a boolean field selected:true, while the rest of the items have selected:false. There's an edge where the selector is wrong and no item is selected.
E.g. For the request GET /someapi?id=bbb
Response
{ foo: xxxy, bar: 123, baz: [
{ id: 'aaa', selected: false, .... },
{ id: 'bbb', selected: true, .... },
{ id: 'ccc', selected: false, .... }
] }
Of course the selected item can be anywhere in the list. So I had in mind an assertion like this pseudo code -
jsonPath('$.baz[?(#.id == fromRequest().query("id"))].selected', byEquality( true ) )
But I can't do that fromRequest() stuff in the JSONPath statement. Right now I guess I could simply have the whole response body as the spec, but that seems unwieldy. If it must be, that's fine I guess.
Any ideas or help appreciated.
I have a DynamoDB table:
+--------------------------------------------------+
| Customer ID (Primary Key)|Gamestats (JSON entry) |
+--------------------------------------------------+
JSON:
{
"Gamestats": [
{
"ID": "QuickShootingMode",
"status": 1
},
{
"ID": "FastReloadMode", // Just want to update this and not update the entire JSON
"status": 0
}
],
"CustomerID": "xyz"
}
I want to update only parts of the JSON. What is the best way to do it? Eg, update the QuickShootingMode to be false.
One way is to make a call and fetch the JSON and then Iterate the JSON and update the value and then put the new JSON back in dynamo DB. It means it would make 2 calls
A) to get the data and
B) to put the data in DB.
Is there a better way by which I could directly update the data and avoid making these extra network calls? I could convert each key of the JSON to be a column in dynamo BD, but if the number of keys grows then I’ll end up having lots of column (which might be a bad design), hence I think having the JSON saved in one column Game stats would make more sense.
Map<String, AttributeValue> key = new HashMap<>();
AmazonDynamoDB dynamoDB = dynamoDBClient.getDynamoDB();
key.put(USER_ID_KEY, new AttributeValue().withS("xyz"));
key.put("Gamedata", new AttributeValue().withS("some JSON"));
PutItemRequest request = new PutItemRequest()
.withTableName(table)
.withItem(key);
PutItemResult result = dynamoDB.putItem(request);
Is there a better way to achieve what I want?
It looks like from your question you are storing stringified JSON. If so an update won't help you, but as far as I can tell there is no value in storing stringified JSON instead of using dynamodb maps and lists.
You can use an update to set a nested attribute in a map or a list. Using a map instead of a list for the gamestats attribute is better because then you don't have to worry about the order of the attributes.
Javascript example with Gamestats being a map.
dynamodb.update({
TableName: table,
Key: key,
UpdateExpression: 'SET #gs.#qs.#status = :newStatus',
ExpressionAttributeNames: {'#gs': 'Gamestats', '#qs': 'QuickShootingMode', '#status': 'status' },
ExpressionAttributeValues: { ':newStatus': false }
}, callback)