How to add items to a map in DynamoDB - amazon-dynamodb

I'm using the AWS.DynamoDB.DocumentClient with nodejs (lambda functions on AWS)
I've to a db called Translations, primary key Term, sort key Category.
Basically I'm trying to write data in like this:
{
Term: 'hello_there',
Category: 'common_phrases',
Translations: {
en-ca: 'Hello There!'
}
}
and I want to update Translations Map to perhaps add another language, or just modify the en-ca portion of the object.
I've tried the following:
let params = {
TableName: 'Translations',
Key: {
Term: 'hello_there',
Category: 'common_phrases',
},
UpdateExpression:
'SET Translations.#lang = list_append(Translations, :term)',
ExpressionAttributeValues: {
':term': 'french version',
},
ExpressionAttributeNames: {
'#lang': 'fr-ca',
},
}
But I get an error about the wrong operand type.
I've tried:
UpdateExpression:
'SET Translations.#lang = :term',
ExpressionAttributeValues: {
':term': 'french version',
},
ExpressionAttributeNames: {
'#lang': 'fr-ca',
},
But this overwrites the entire contents of the Translations field. Meaning that if I already had en-ca in there, now I would only have fr-ca.
I tried this as well, but also get an operand error:
{
UpdateExpression: 'ADD Translations :term',
ExpressionAttributeValues: {
':term': { 'fr-ff': 'frenchterm' },
},
Any suggestions on how to add/update items to the Translations Map?

Your SET expression was close, try something like this:
UpdateExpression:
'SET #trans.#lang = :term',
ExpressionAttributeValues: {
':term': 'french version',
},
ExpressionAttributeNames: {
'#trans': 'Translations`,
'#lang': 'fr-ca',
},

Related

DynamoDB update map value only if versions match

I have the following schema:
{
balance: {
customData: string,
version: number
}
}
I need to update balance.customData only if version == 2. Once update operation succeeds, I need to increment version by 1.
I tried the following update transaction
Update: {
Key: {
'pk': pk,
'sk': sk
},
TableName: this.config.getTable(),
UpdateExpression: 'SET #balance.#customData = :customData, #balance.#version = #balance.#version + :incr',
ConditionExpression: '#balance.#customData.#version = :version',
ExpressionAttributeNames: {
'#customData': 'customData',
'#balance': 'balance',
'#version': 'version'
},
ExpressionAttributeValues: {
':customData': balance.customData,
':version': balance.version,
':incr': {'N': 1},
}
}
But when I run this, I get ValidationException: Invalid UpdateExpression: Incorrect operand type for operator or function; operator or function: +, operand type: M
I assume I'm not providing correct syntax to increment map value.
Even if I remove increment part
Update: {
Key: {
'pk': pk,
'sk': sk
},
TableName: this.config.getTable(),
UpdateExpression: 'SET #balance.#customData = :customData,
ConditionExpression: '#balance.#customData.#version = :version',
ExpressionAttributeNames: {
'#customData': 'customData',
'#balance': 'balance',
'#version': 'version'
},
ExpressionAttributeValues: {
':customData': balance.customData,
':version': balance.version
}
}
I still get ValidationError with reason Other, which is not very helpful. Can you please help me understand what I'm doing wrong? Thanks

Why does Dynamo DB throw an error when updating a map key with the same value?

I am trying to run a simple update query, but got an error when I tried to update the key of a map to the same value. Is there a technical reason this would be disallowed? or some kind of best-practice that I am violating by trying to do this?
Error:
ValidationException: Invalid UpdateExpression: Two document paths overlap with each other;
must remove or rewrite one of these paths; path one: [questions, What is xx?], path two: [questions, What is xx?]
Query object:
{
TableName: 'notesTable',
Key: { topic: 'My tooic' },
ExpressionAttributeNames: { '#qq': 'What is xx?', '#updq': 'What is xx?' },
ExpressionAttributeValues: { ':updans': 'new answer' },
UpdateExpression: 'REMOVE questions.#qq SET questions.#updq = :updans'
}
Multiple ways to deal with scenario when same key needs to be updated. Instead of removing and updating the same key, we can simply SET the key , which replaced the value anyhow.
So, simple way is to send different updateExpression each time.
const qq = "What is xx2?";
const updq = "What is xx?";
let expressionAttributeNames;
let UpdateExpression;
if (qq === updq) {
expressionAttributeNames = { "#updq": "What is xx?" };
UpdateExpression = "SET questions.#updq = :updans";
} else {
expressionAttributeNames = { "#qq": "What is xx1?", "#updq": "What is xx?" };
UpdateExpression = "REMOVE questions.#qq SET questions.#updq = :updans";
}
docClient.update(
{
TableName: "test",
Key: {
id: "My tooic",
},
ExpressionAttributeNames: expressionAttributeNames,
ExpressionAttributeValues: { ":updans": "new answer1" },
UpdateExpression: UpdateExpression,
},
function (error, result) {
console.log("error", error, "result", result);
}
);

Dynamodb - Condition Expression with ExpressionAttributeNames not working

Am trying to do a conditional update and since the field name is a reserved keyword, am using ExpressionAttributeNames to pass in the column name for the condition. The update part isn't working if i use the ExpressionAttributeNames. Any thoughts?
Update: {
Key: {
"pk": "sb#prd#" + productId,
"sk": productId.toString()
},
TableName: 'test',
ConditionExpression: '#minQty >= :minQty',
UpdateExpression: "set sold_count = :sold_count",
ExpressionAttributeNames: {
"#minQty" : "variant[0].items[0].availableQty"
},
ExpressionAttributeValues: {
":sold_count" : 1,
":minQty" : 1
},
}
The aliases defined in ExpressionAttributeNames can only be a single attribute name - they cannot be full paths like variant[0].items[0].availableQty.
You can do something like:
ConditionExpression: '#v[0].#i[0].#a >= :minQty',
ExpressionAttributeNames: {
"#v" : "variant",
"#i" : "items",
"#a" : "availableQty"
},

DyanamoDB SCAN with nested attribute

Can I scan DynamoDB by 'order.shortCode', in the given example. The console is indicating I can't with dot notation, and I can't find any documentation on it.
{
"key2": "cj11b1ygp0000jcgubpe5mso3",
"order": {
"amount": 74.22,
"dateCreated": "2017-04-02T19:15:33-04:00",
"orderNumber": "cj11b1ygp0000jcgubpe5mso3",
"shortCode": "SJLLDE"
},
"skey2": "SJLLDE"
}
To scan by a nested attribute, you should use ExpressionAttributeNames parameter to pass each path component (i.e. order and shortCode) separately into FilterExpression like shown below:
var params = {
TableName: 'YOUR_TABLE_NAME',
FilterExpression: "#order.#shortCode = :shortCodeValue",
ExpressionAttributeNames: {
'#order': 'order',
"#shortCode": "shortCode"
},
ExpressionAttributeValues: {
':shortCodeValue': 'SJLLDE'
}
};
dynamodbDoc.scan(params, function(err, data) {
});
Here is a link to documentation explaining this:
http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.ExpressionAttributeNames.html#Expressions.ExpressionAttributeNames.NestedAttributes

How to create and populate lists in DynamoDB

I wish to create an Item in DynamoDB that is a list. This is my code:
var list_update_params = {
TableName: "table01",
Key: {
"MachineID": {
"S": MachineID
},
"Hour": {
"S": Hour
}
},
UpdateExpression: "set var01_list = list_append(var01_list, :ot)",
ExpressionAttributeValues: {
":ot": {"L": [{"N": var01}]}
},
ReturnValues: "NONE"
};
dynamodb.updateItem(list_update_params, function(err, data) {
if (err) console.log(err, err.stack);
else console.log("Updated List to DynamoDB");
});
The problem is list_append expects the attribute var01_list to already be present, but I wouldn't know at the first insert. Is there a technique where it'll let me create an insert a List attribute if one doesn't exist and append to it in later calls?
Got the answer from a similar post here.
UpdateExpression: "set var01_list= list_append(if_not_exists(var01_list, :empty_list), :h)",
ExpressionAttributeValues: {
":h": {"L": [{"N":var01}]},
":empty_list": {"L": []}
},
The key was using if_not_exists with list_append. Didn't know that could be done in this matter

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