I am using Amazon RDS with AppSync. I've created a resolver that join two tables to get One-to-One association between them and returns columns from both tables. What I would like to do is to be able to put nest some columns under a key in the resulting parsed JSON object evaluated using $util.rds.toJSONObject().
Here's the schema:
type Parent {
col1: String
col2: String
child: Child
}
type Child {
col3: String
col4: String
}
Here's the resolver:
{
"version": "2018-05-29",
"statements": [
"SELECT parent.*, child.col3 AS `child.col3`, child.col4 AS `child.col4` FROM parent LEFT JOIN child ON parent.col1 = child.col3"
]
}
I tried naming the resulting column with dot-syntax but, $util.rds.toJSONObject() doesn't put col3 and col4 under child key. The reason it should is because otherwise, Apollo won't be able to cache and parse the entity.
Note: Dot-syntax is not documented anywhere. Usually, some ORMs use dot-syntax technique to convert SQL rows to proper nested JSON objects.
The #Aaron_H comment and answer were useful for me, but the response mapping template provided in the answer didn't work for me.
I managed to get a working response mapping template for my case which is similar for the case in question. In images below you will find info for query -> message(id: ID) { ... } (one message and the associated user will be returned):
SQL request to user table;
SQL request to message table;
SQL JOIN tables request for message id=1;
GraphQL Schema;
Request and response templates;
AWS AppSync query.
https://github.com/xai1983kbu/apollo-server/blob/pulumi_appsync_2/bff_pulumi/graphql/resolvers/Query.message.js
Next example for query messages
https://github.com/xai1983kbu/apollo-server/blob/pulumi_appsync_2/bff_pulumi/graphql/resolvers/Query.messages.js
Assuming your resolver is expecting to return a list of Parent types, ie. [Parent!]!, you can write your response mapping template logic like this:
#if($ctx.error)
$util.error($ctx.error.message, $ctx.error.type)
#end
#set($output = $utils.rds.toJsonObject($ctx.result)[0])
## Make sure to handle instances where fields are null
## or don't exist according to your business logic
#foreach( $item in $output )
#set($item.child = {
"col3": $item.get("child.col3"),
"col4": $item.get("child.col4")
})
#end
$util.toJson($output)
Related
I'm new to DynamoDb and the intricacies of querying it - I understand (hopefully correctly) that I need to either have a partition Key or Global Secondary Index (GSI) in order to query against that value in the table.
I know I can use Appsync to query on a GSI by setting up a resolver - and this works. However, I have a setup using the Java AWS CDK (I'm writing in Kotlin) where I'm using Appsync and routing my queries into lambda Resolvers (so that once this works, I can do more complicated things later).
The Crux of the issue is that when I setup a Lambda to resolve my query, I end up with this Error msg: com.amazonaws.services.dynamodbv2.model.AmazonDynamoDBException: Query condition missed key schema element: testName returned from the Lambda.
I think these should be the key snippets..
My DynamoDbBean..
#DynamoDbBean
data class Test(
#get:DynamoDbPartitionKey var id: String = "",
#get:DynamoDbSecondaryPartitionKey(indexNames = ["testNameIndex"])
var testName: String = "",
)
Using the CDK I Created GSI on
testTable.addGlobalSecondaryIndex(
GlobalSecondaryIndexProps.builder()
.indexName("testNameIndex")
.partitionKey(
Attribute.builder()
.name("testName")
.type(AttributeType.STRING)
.build()
)
.projectionType(ProjectionType.ALL)
.build())
Then, within my Lambda I am trying to query my DynamoDb table, using a fixed value here testName = A.
My Sample data in the Test table would be like so..
{
"id" : "SomeUUID",
"testName" : "A"
}
private var client: AmazonDynamoDB = AmazonDynamoDBClientBuilder.standard().build()
private var dynamoDB: DynamoDB = DynamoDB(client)
Lambda Resolver Snippets...
val table: Table = dynamoDB.getTable(TABLE_NAME)
val index: Index = table.getIndex("testNameIndex")
...
QuerySpec().withKeyConditionExpression("testNameIndex = :testName")
.withValueMap(ValueMap().withString(":testName", "A"))
val iterator: Iterator<Item> = index.query(querySpec).iterator()
while (iterator.hasNext()) {
logger.info(iterator.next().toJSONPretty())
}
This is what results in this Error msg: com.amazonaws.services.dynamodbv2.model.AmazonDynamoDBException: Query condition missed key schema element: testName
Am I on the wrong lines here? I know there is some mixing of libs between the 'enhanced' Dynamo sdk and the dynamodbv2 sdk - so if there is a better way of doing this query, I'd love to know!
Thanks!
Your QuerySpec's withKeyConditionExpression is initialized wrong. You need to init it like.
not testNameIndex it should be testName
QuerySpec().withKeyConditionExpression("testName = :testName")
.withValueMap(ValueMap().withString(":testName", "A"))
I've currently been handling batch operations with a for loop, but obviously, this is not the best approach, especially as I'm adding an 'upload by CSV' option, which will take 1000+ putItems.
I searched around for the best ways to implement this, specifically this link:
https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-dynamodb-batch.html
However, even after following those steps mentioned I'm not able to achieve a batch operation. Below is my code for a 'batch delete' operation.
Here is my schema.graphql file:
type Client #model #auth(rules: [{ allow: owner }]) {
id: ID!
name: String!
company: String
phone: String
email: String
}
type Mutation {
batchDelete(ids: [ID]): [Client]
}
I then create two new files. One request mapping template and one response mapping template.
#set($clientsdata = [])
#foreach($item in ${ctx.args.clients})
$util.qr($clientsdata.delete($util.dynamodb.toMapValues($item)))
#end
{
"version" : "2018-05-29",
"operation" : "BatchDeleteItem",
"tables" : {
"Clients": $utils.toJson($clientsdata)
}
}
and then as per the tutorial a "simple pass through" response mapping template:
$util.toJson($ctx.result.data.Posts)
However now when I run the batchdelete command, I keep getting nothing returned.
Would really appreciate guidance on this!
When it comes to performing DynamoDB batch operations in tandem with Amplify, note that the table name specified in the schema is actually different per environment, i.e. your "Client" table wouldn't be recognized as "Clients" as you have stated it in the request mapping template, but rather the name it is given on Amplify push, per environment.
E.g. Client-<some alphanumeric number>-envName
Add the full name of the table to your request and response mapping templates.
Also your foreach statement should read:
#foreach($item in ${ctx.args.clientsdata}) wherein you iterate through each of the items in the array that is passed as the argument to the context object.
Hope this helps.
Does AppSync support nested single mutation?
I want to call a single mutation which will insert records into two tables, eg: User and Roles tables in DynamoDB.
Something like this for example:
createUser(
input: {
Name: "John"
Email: "user#domain.com"
LinesRoles: [
{ Name: "Role 1" }
{ Name: "Role 2" }
]
}) {
Id
Name
LinesRoles {
Id
Name
}
}
Do I need to create two resolvers in AppSync for User and Roles to insert the records in both tables?
I can think of three ways to achieve this:
Use a BatchPutItem to save records into two tables at once. However, you won’t be able to use any ConditionExpression
Use a pipeline resolver with two AppSync functions where one function makes a PutItem to the Roles table and the other to the User table. However, you need to be ok with potentially inconsistent scenarios where the record has been inserted in one table but not in the other.
Use a Lambda resolver that does the write to 2 tables inside a DynamoDB transaction.
So here is my schema:
type Model {
PartitionKey: ID!
Name: String
Version: Int
FBX: String
# ms since epoch
CreatedAt: AWSTimestamp
Description: String
Tags: [String]
}
type Query {
getAllModels(count: Int, nextToken: String): PaginatedModels!
}
type PaginatedModels {
models: [Model!]!
nextToken: String
}
I would like to call 'getAllModels' and have all of it's data, and all of it's tags be filled in.
But here is the thing. Tags are stored via sort keys. Like so
PartionKey | SortKey
Model-0 | Model-0
Model-0 | Tag-Tree
Model-0 | Tag-Building
Is it possible to transform the 'Tag' sort keys into the Tags: [String] array in the schema via a DynamoDB resolver? Or must I do something extra fancy through a lambda? Or is there a smarter way to do this?
To clarify, are you storing objects like this in DynamoDB:
{ PartitionKey (HASH), Tag (SortKey), Name, Version, FBX, CreatedAt, Description }
and using a DynamoDB Query operation to fetch all rows for a given HashKey.
Query #PartitionKey = :PartitionKey
and getting back a list of objects some of which have a different "Tag" value and one of which is "Model-0" (aka the same value as the partition key) and I assume that record contains all other values for the record. E.G.
[
{ PartitionKey, Tag: 'ValueOfPartitionKey', Name, Version, FBX, CreatedAt, ... },
{ PartitionKey, Tag: 'Tag-Tree' },
{ PartitionKey: Tag: 'Tag-Building' }
]
You can definitely write resolver logic without too much hassle that reduces the list of model objects into a single object with a list of "Tags". Let's start with a single item and see how to implement a getModel(id: ID!): Model query:
First define the response mapping template that will get all rows for a partition key:
{
"version" : "2017-02-28",
"operation" : "Query",
"query" : {
"expression": "#PartitionKey = :id",
"expressionValues" : {
":id" : {
"S" : "${ctx.args.id}"
}
},
"expressionNames": {
"#PartitionKey": "PartitionKey" # whatever the table hash key is
}
},
# The limit will have to be sufficiently large to get all rows for a key
"limit": $util.defaultIfNull(${ctx.args.limit}, 100)
}
Then to return a single model object that reduces "Tag" to "Tags" you can use this response mapping template:
#set($tags = [])
#set($result = {})
#foreach( $item in $ctx.result.items )
#if($item.PartitionKey == $item.Tag)
#set($result = $item)
#else
$util.qr($tags.add($item.Tag))
#end
#end
$util.qr($result.put("Tags", $tags))
$util.toJson($result)
This will return a response like this:
{
"PartitionKey": "...",
"Name": "...",
"Tags": ["Tag-Tree", "Tag-Building"],
}
Fundamentally I see no problem with this but its effectiveness depends upon your query patterns. Extending this to the getAll use is doable but will require a few changes and most likely a really inefficient Scan operation due to the fact that the table will be sparse of actual information since many records are effectively just tags. You can alleviate this with GSIs pretty easily but more GSIs means more $.
As an alternative approach, you can store your Tags in a different "Tags" table. This way you only store model information in the Model table and tag information in the Tag table and leverage GraphQL to perform the join for you. In this approach have Query.getAllModels perform a "Scan" (or Query) on the Model table and then have a Model.Tags resolver that performs a Query against the Tag table (HK: ModelPartitionKey, SK: Tag). You could then get all tags for a model and later create a GSI to get all models for a tag. You do need to consider that now the nested Model.Tag query will get called once per model but Query operations are fast and I've seen this work well in practice.
Hope this helps :)
I have entities that look like that:
{
name: "Max",
nicknames: [
"bestuser"
]
}
how can I query for nicknames to get the name?
I have created the following index,
indexes:
- kind: users
properties:
- name: name
- name: nicknames
I use the node.js client library to query the nickname,
db.createQuery('default','users').filter('nicknames', '=', 'bestuser')
the response is only an empty array.
Is there a way to do that?
You need to actually fetch the query from datastore, not just create the query. I'm not familiar with the nodejs library, but this is the code given on the Google Cloud website:
datastore.runQuery(query).then(results => {
// Task entities found.
const tasks = results[0];
console.log('Tasks:');
tasks.forEach(task => console.log(task));
});
where query would be
const query = db.createQuery('default','users').filter('nicknames', '=', 'bestuser')
Check the documentation at https://cloud.google.com/datastore/docs/concepts/queries#datastore-datastore-run-query-nodejs
The first point to notice is that you don't need to create an index to this kind of search. No inequalities, no orders and no projections, so it is unnecessary.
As Reuben mentioned, you've created the query but you didn't run it.
ds.runQuery(query, (err, entities, info) => {
if (err) {
reject(err);
} else {
response.resultStatus = info.moreResults;
response.cursor = info.moreResults == TNoMoreResults? null: info.endCursor;
resolve(entities);
};
});
In my case, the response structure was made to collect information on the cursor (if there is more data than I've queried because I've limited the query size using limit) but you don't need to anything more than the resolve(entities)
If you are using the default namespace you need to remove it from your query. Your query needs to be like this:
const query = db.createQuery('users').filter('nicknames', '=', 'bestuser')
I read the entire plob as a string to get the bytes of a binary file here. I imagine you simply parse the Json per your requirement