I'm trying to store the id of a record within the record. I am aware I could just use a where statement to find the last ID and increment by one but I was curious is it possible to get the ID of the record whilst its been made.
$ScreenshotOBJ = Screenshots::create([
"CollectionID" => $ScreenshotOBJ->id,
//This isn't the whole record just the important part
]);
Is this possible it throws an error saying the variable doesn't exist.
You could make the CollectionID field nullable. And then in the boot method of your Screenshots model, you can set the CollectionID like this,
protected static function boot()
{
parent::boot();
static::created(function ($screenshot) {
$screenshot->update(
['CollectionID' => $screenshot->id)]
);
});
}
Using Microsoft.Azure.ActiveDirectory.GraphClient.ActiveDirectoryClient api I am trying to find an existing Application in AAD which has the same as my desired IdentifierUrl. This is so i can decide on creating one or leaving the existing one alone.
I'm using the following calls. However I get this error:
The collection property 'identifierUris' cannot be used in a 'where' query expression. Collection properties are only supported as the source of 'any' or 'all' methods in a 'where' query option
What is the recommended way of doing this? thanks
public static async Task<IApplication> FindApplicationByUrlAsync(string accessToken, string tenantId, string identifierUrl)
{
var graphClient = NewActiveDirectoryClient(accessToken, tenantId);
var matches = await graphClient.Applications.Where(app => app.IdentifierUris.Contains(identifierUrl)).ExecuteAsync();
return matches.CurrentPage.ToList().FirstOrDefault();
}
Use the Any function:
var result = await client.Applications.Where(a => a.IdentifierUris.Any(i => i == identifierUri)).ExecuteAsync();
That'll get translated into a request as follows:
https://graph.microsoft.com/beta/applications?$filter=identifierUris/any(c:c eq 'yourIdentifierUri')
More info on filters for the Azure AD Graph here:
https://msdn.microsoft.com/en-us/library/azure/ad/graph/howto/azure-ad-graph-api-supported-queries-filters-and-paging-options
I am trying to get to Web API GET controller using $http.get in angular application as follows :
$http.get(BasePath + '/api/documentapi/GetDocuments/' ,
{
params: {
PrimaryID: ID1,
AlternateID: ID2,
}
}).then( ...
In my case, either the PrimaryID or the AlternateID will have the value. So, one of them will be null always.
My Web api method is
public DocumentsDto[] GetDocuments(decimal? PrimaryID, decimal? AlternateID)
{ ...
When one of the value is null, the url generated by $http.get is as follows :
http://BaseServerPath/api/documentapi/GetDocuments/?PrimaryID=1688
or
http://BaseServerPath/api/documentapi/GetDocuments/?AlternateID=154
This does not hit my Web API method.
However if I use
http://BaseServerPath/api/documentapi/GetDocuments/?PrimaryID=1688&AlternateID=null
it works. I can hardcode the values to null in my params, however I would like to know if there is any correct way to achieve this.
Thanks,
Sam
I got the correct answer from #RobJ. He has posted a link to the answer. I am pasting the same answer here as well. The solution is to have default values for the Web API parameters.
public string GetFindBooks(string author="", string title="", string isbn="", string somethingelse="", DateTime? date= null)
{
// ...
}
In my case it will be
public DocumentsDto[] GetDocuments(decimal? PrimaryID = null, decimal? AlternateID = null)
{ ...
Although you've specified on your Web API controller that the two parameters can be null, the ASP.NET routing engine will still be looking for two parameters in a call to that method - even if one of them is null.
Ideally, you'd create two methods, one which takes just the primary and one just the secondary but in your case this is slightly tricky as both your IDs are of the same type. Although you can specify which parameter corresponds to the supplied value in the query string, both these methods will have the same signature (a single parameter of type decimal) in your controller class.
So you have two options here. Either create new controller so you have one which receives queries for the PrimaryID and one for the SecondaryID, or you have one method which takes an object containing one ID set to a value and the other to null, and run your query based on that.
And yet another option can be to convert the request params to a complex object and use [FromUri] to create the object from Url.
you can try this:
$http.get(BasePath + '/api/documentapi/GetDocuments/' ,
{
params: {
PrimaryID: ID1!=undefined?ID1:0,
AlternateID: ID2!=undefined?ID2:0,
}
}).then( ...
then you can handle 0 in webapi...
I have a many-to-many structure mapped to entity framework. This is a sample of what it looks like:
User UserTag Tag
------- -------- -------
IdUser(PK) IdUserTag(PK) IdTag(PK)
Name IdUser(FK) TagName
Desc IdTag(FK) Active
Now, I needed to exclude from any request of any method the viewing of Tags that were Active=false.
First, I tried doing it manually in every method, like:
public User GetById(int id)
{
var item = UserRepository.GetById(id); //This is just a repository that calls the EF context
//EF automatically maps it to the *UserTags* property
foreach(var tag in item.UserTags)
{
if(tag.Tag.Active == false)
item.UserTags.Remove(tag);
}
}
But it throws the following exception:
The relationship could not be changed because one or more of the foreign-key properties is non-nullable
So, I wanted to know if there's a way to conditionaly filter every request made to a specific table, whether it is select or a join request.
Try this in your GetById method:
var user.UserTags = dbContext.Entry(user)
.Collection(u => u.UserTags)
.Query()
.Where(ut => ut.Active == true)
.ToList();
The supplied code fails because it is attempting to remove items from the data entities not the list. If you want to pass the data entity around instead of the data model, you need to not use Remove. Something like the below (untested should work).
tags = item.UserTags.Where((ut) => ut.Active).ToList();
This line will get you a list of data entities that are active. However, you should really map all of this into a data model (see AutoMapper) and then you would not be removing items from the database.
In my db scheme, I need a autoincrement primary key. How I can realize this feature?
PS For access to DynamoDB, I use dynode, module for Node.js.
Disclaimer: I am the maintainer of the Dynamodb-mapper project
Intuitive workflow of an auto-increment key:
get the last counter position
add 1
use the new number as the index of the object
save the new counter value
save the object
This is just to explain the underlying idea. Never do it this way because it's not atomic. Under certain workload, you may allocate the same ID to 2+ different objects because it's not atomic. This would result in a data loss.
The solution is to use the atomic ADD operation along with ALL_NEW of UpdateItem:
atomically generate an ID
use the new number as the index of the object
save the object
In the worst case scenario, the application crashes before the object is saved but never risk to allocate the same ID twice.
There is one remaining problem: where to store the last ID value ? We chose:
{
"hash_key"=-1, #0 was judged too risky as it is the default value for integers.
"__max_hash_key__y"=N
}
Of course, to work reliably, all applications inserting data MUST be aware of this system otherwise you might (again) overwrite data.
the last step is to automate the process. For example:
When hash_key is 0:
atomically_allocate_ID()
actual_save()
For implementation details (Python, sorry), see https://bitbucket.org/Ludia/dynamodb-mapper/src/8173d0e8b55d/dynamodb_mapper/model.py#cl-67
To tell you the truth, my company does not use it in production because, most of the time it is better to find another key like, for the user, an ID, for a transaction, a datetime, ...
I wrote some examples in dynamodb-mapper's documentation and it can easily be extrapolate to Node.JS
If you have any question, feel free to ask.
Another approach is to use a UUID generator for primary keys, as these are highly unlikely to clash.
IMO you are more likely to experience errors consolidating primary key counters across highly available DynamoDB tables than from clashes in generated UUIDs.
For example, in Node:
npm install uuid
var uuid = require('uuid');
// Generate a v1 (time-based) id
uuid.v1(); // -> '6c84fb90-12c4-11e1-840d-7b25c5ee775a'
// Generate a v4 (random) id
uuid.v4(); // -> '110ec58a-a0f2-4ac4-8393-c866d813b8d1'
Taken from SO answer.
If you're okay with gaps in your incrementing id, and you're okay with it only roughly corresponding to the order in which the rows were added, you can roll your own: Create a separate table called NextIdTable, with one primary key (numeric), call it Counter.
Each time you want to generate a new id, you would do the following:
Do a GetItem on NextIdTable to read the current value of Counter --> curValue
Do a PutItem on NextIdTable to set the value of Counter to curValue + 1. Make this a conditional PutItem so that it will fail if the value of Counter has changed.
If that conditional PutItem failed, it means someone else was doing this at the same time as you were. Start over.
If it succeeded, then curValue is your new unique ID.
Of course, if your process crashes before actually applying that ID anywhere, you'll "leak" it and have a gap in your sequence of IDs. And if you're doing this concurrently with some other process, one of you will get value 39 and one of you will get value 40, and there are no guarantees about which order they will actually be applied in your data table; the guy who got 40 might write it before the guy who got 39. But it does give you a rough ordering.
Parameters for a conditional PutItem in node.js are detailed here. http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/frames.html#!AWS/DynamoDB.html. If you had previously read a value of 38 from Counter, your conditional PutItem request might look like this.
var conditionalPutParams = {
TableName: 'NextIdTable',
Item: {
Counter: {
N: '39'
}
},
Expected: {
Counter: {
AttributeValueList: [
{
N: '38'
}
],
ComparisonOperator: 'EQ'
}
}
};
For those coding in Java, DynamoDBMapper can now generate unique UUIDs on your behalf.
DynamoDBAutoGeneratedKey
Marks a partition key or sort key property as being auto-generated.
DynamoDBMapper will generate a random UUID when saving these
attributes. Only String properties can be marked as auto-generated
keys.
Use the DynamoDBAutoGeneratedKey annotation like this
#DynamoDBTable(tableName="AutoGeneratedKeysExample")
public class AutoGeneratedKeys {
private String id;
#DynamoDBHashKey(attributeName = "Id")
#DynamoDBAutoGeneratedKey
public String getId() { return id; }
public void setId(String id) { this.id = id; }
As you can see in the example above, you can apply both the DynamoDBAutoGeneratedKey and DynamoDBHashKey annotation to the same attribute to generate a unique hash key.
Addition to #yadutaf's answer
AWS supports Atomic Counters.
Create a separate table (order_id) with a row holding the latest order_number:
+----+--------------+
| id | order_number |
+----+--------------+
| 0 | 5000 |
+----+--------------+
This will allow to increment order_number by 1 and get the incremented result in a callback from AWS DynamoDB:
config={
region: 'us-east-1',
endpoint: "http://localhost:8000"
};
const docClient = new AWS.DynamoDB.DocumentClient(config);
let param = {
TableName: 'order_id',
Key: {
"id": 0
},
UpdateExpression: "set order_number = order_number + :val",
ExpressionAttributeValues:{
":val": 1
},
ReturnValues: "UPDATED_NEW"
};
docClient.update(params, function(err, data) {
if (err) {
console.log("Unable to update the table. Error JSON:", JSON.stringify(err, null, 2));
} else {
console.log(data);
console.log(data.Attributes.order_number); // <= here is our incremented result
}
});
🛈 Be aware that in some rare cases their might be problems with the connection between your caller point and AWS API. It will result in the dynamodb row being incremented, while you will get a connection error. Thus, there might appear some unused incremented values.
You can use incremented data.Attributes.order_number in your table, e.g. to insert {id: data.Attributes.order_number, otherfields:{}} into order table.
I don't believe it is possible to to a SQL style auto-increment because the tables are partitioned across multiple machines. I generate my own UUID in PHP which does the job, I'm sure you could come up with something similar like this in javascript.
I've had the same problem and created a small web service just for this purpose. See this blog post, that explains how I'm using stateful.co with DynamoDB in order to simulate auto-increment functionality: http://www.yegor256.com/2014/05/18/cloud-autoincrement-counters.html
Basically, you register an atomic counter at stateful.co and increment it every time you need a new value, through RESTful API. The service is free.
Auto Increment is not good from performance perspective as it will overload specific shards while keeping others idle, It doesn't make even distribution if you're storing data to Dynamodb.
awsRequestId looks like its actually V.4 UUID (Random), code snippet below to try it:
exports.handler = function(event, context, callback) {
console.log('remaining time =', context.getRemainingTimeInMillis());
console.log('functionName =', context.functionName);
console.log('AWSrequestID =', context.awsRequestId);
callback(null, context.functionName);
};
In case you want to generate this yourself, you can use https://www.npmjs.com/package/uuid or Ulide to generate different versions of UUID based on RFC-4122
V1 (timestamp based)
V3 (Namespace)
V4 (Random)
For Go developers, you can use these packages from Google's UUID, Pborman, or Satori. Pborman is better in performance, check these articles and benchmarks for more details.
More Info on Universal Unique Identifier Specification could be found here.
Create the new file.js and put this code:
exports.guid = function () {
function _p8(s) {
var p = (Math.random().toString(16)+"000000000").substr(2,8);
return s ? "-" + p.substr(0,4) + "-" + p.substr(4,4) : p ;
}
return (_p8() + _p8(true) + _p8(true)+new Date().toISOString().slice(0,10)).replace(/-/g,"");
}
Then you can apply this function to the primary key id. It will generate the UUID.
Incase you are using NoSQL DynamoDB then using Dynamoose ORM, you can easily set default unique id. Here is the simple user creation example
// User.modal.js
const dynamoose = require("dynamoose");
const userSchema = new dynamoose.Schema(
{
id: {
type: String,
hashKey: true,
},
displayName: String,
firstName: String,
lastName: String,
},
{ timestamps: true },
);
const User = dynamoose.model("User", userSchema);
module.exports = User;
// User.controller.js
const { v4: uuidv4 } = require("uuid");
const User = require("./user.model");
exports.create = async (req, res) => {
const user = new User({ id: uuidv4(), ...req.body }); // set unique id
const [err, response] = await to(user.save());
if (err) {
return badRes(res, err);
}
return goodRes(res, reponse);
};
Instead of using UUID use KSUID for ids. Naturally ordered by generation time.
https://www.npmjs.com/package/ksuid?activeTab=readme