I use Hasura and I have a social-network like situation.
In which I have a "User" object and a "Feed" object.
Every user has a feed.
I have a relationship from user.id to feed.id.
The relevant mutation is UpsertUserDetails as follows:
mutation UserDetailsUpsert(
$email: String!
$picture: String
) {
insert_users_one(
object: {
email: $email
feed: { data: {} }
picture: $picture
}
on_conflict: { constraint: users_tid_email_key, update_columns: [picture] }
) {
id
}
}
So when I create a new user it also creates a feed for it.
But when I only update user details I don't want it to create a new feed.
I would like to stop the upsert from going through to relationships instead of the above default behavior.
and according to this manual I don't see if its even possible: https://hasura.io/docs/latest/graphql/core/databases/postgres/mutations/upsert.html#upsert-in-nested-mutations
To allow upserting in nested cases, set update_columns: []. By doing this, in case of a conflict, the conflicted column/s will be updated with the new value (which is the same values as they had before and hence will effectively leave them unchanged) and will allow the upsert to go through.
Thanks!
I'd recommend that you design your schema such that bad data cannot be entered in the first place. You can put partial unique indices on the feed table in order to prevent duplicate feeds from ever being created. Since you have both users and groups you can implement it with 2 partial indices.
CREATE UNIQUE INDEX unique_feed_per_user ON feed (user_id)
WHERE user_id IS NOT NULL;
CREATE UNIQUE INDEX unique_feed_per_group ON feed (group_id)
WHERE group_id IS NOT NULL;
Related
I am creating a collection of judges and courthouses. Every judge will be assigned to one courthouse. I have set up my relation to be that courthouse has many judges
I am attempting to do this programmatically when the app loads. I have a function that is able to populate all the fields in judge except the relation to courthouse. My function uses the Strapi API like this
const judge = await strapi.query('judge').create({
name: data[i].name,
},
{
courthouse: data[i].courthouse_name // here is where I think the relation is created
}
)
I am passing in a string that has the name of courthouse, because I don't know the ID of the courthouse in the Courthouse collection.
My question is it possible to create a relation to another collection by anything other than an ID? How can I create a relation to a courthouse by its name?
I couldn't find a way around building a relationship between two models without the ID, so I created a custom solution using the Strapi lifecycle hooks
Essentially what I did I utilized the beforeCreate lifecycle hook to query and find the courthouse that matches the name like this:
// judges.js
async beforeCreate(result, data) {
const courthouse = await strapi.query('courthouse').find(
{courthouse_name:data.courthouse}
); // returns the courthouse that matches the name
result['courthouse'] = courthouse[0].id; // populates the relational field with the
// ID of the courthouse
}
The response object contained the courthouse's ID and I manipulated the data that is being sent to the create command like this:
const judge = await strapi.query('judge').create({
name: data[i].name,
courthouse: data[i].courthouse_name
})
The result is an object that looks like this:
{name: 'Garfield Lucas, courthouse: 7463987}
How insert item on top table in PostgreSQL? That it is possible? In the table I have only two fields as text. First is primary key.
CREATE TABLE news_table (
title text not null primary key,
url text not null
);
I need a simple query for the program in java.
OK, this is my code:
get("/getnews", (request, response) -> {
List<News> getNews = newsService.getNews();
List<News> getAllNews = newsService.getAllNews();
try (Connection connection = DB.sql2o.open()) {
String sql = "INSERT INTO news_table(title, url) VALUES (:title, :url)";
for (News news : getNews) {
if (!getAllNews.contains(news)) {
connection.createQuery(sql, true)
.addParameter("title", news.getTitle())
.addParameter("url", news.getUrl())
.executeUpdate()
.getKey();
}
}
}
return newsService.getNews();
}, json());
The problem is that as it calls getnews method for the second time this new news adds at the end of the table, and there is no extant hronologi news. How this resolve? I use Sql2o + sparkjava.
Probably already I know. I need to reverse the List getnews before I will must contains object getnews and getallnews?
There is no start or end in a table. If you want to sort your data, just use an ORDER BY in your SELECT statements. Without ORDER BY, there is no order.
Relational theory, the mathematical foundation of relational databases, lays down certain conditions that relations (represented in real databases as tables) must obey. One of them is that they have no ordering (i.e., the rows will neither be stored nor retrieved in any particular order, since they are treated as a mathematical set). It's therefore completely under the control of the RDBMS where a new row is entered into a table.
Hence there is no way to ensure a particular ordering of the data without using an ORDER BY clause when you retrieve the data.
I was wondering how can i POST in a single request (without fetching results for the given attribute) a pretty simple record to an Algolia Index without creating repeated instances.
e.g:
category: {
name: String // This should be unique
}
There isn't such "addObject if not exists" feature based on the record content but if you use the category name as the objectID of your record; the second time you'll add the object, it will just replace the previous instance.
{
objectID: "mycategoryname",
moreattributes: "if needed",
[...]
}
Would that work?
I am trying to get one query work since morning and not able to get it working I have two tables photographers and reviews please have a look at structure and then I will ask the question at the bottom :
Reviews table :
id int(10) unsigned -> primary key
review text
user_id int(10) unsigned foreign key to users table
user_name varchar(64)
photographer_id int(10) unsigned foreign key to photographers table
Photographers table :
id int(10) unsigned -> primary key
name text
brand text
description text
photo text
logo text
featured varchar(255)
Photographers model :
class Photographer extends Model
{
public function reviews()
{
return $this->hasMany('\App\Review');
}
}
Reviews Model :
class Review extends Model
{
public function photographers()
{
return $this->belongsTo('\App\Photographer');
}
}
My logic to query the records
$response = Photographer::with(['reviews' => function($q)
{
$q->selectRaw('max(id) as id, review, user_id, user_name, photographer_id');
}])
->where('featured', '=', 'Yes')
->get();
The question is : I want to fetch all the photographers who have at least one review in the review table, also I want to fetch only one review which is the most latest, I may have more than one review for a photographer but I want only one.
I would add another relationship method to your Photogrpaher class:
public function latestReview()
{
return $this->hasOne('App\Review')->latest();
}
Then you can call:
Photographer::has('latestReview')->with('latestReview')->get();
Notes:
The latest() method on the query builder is a shortcut for orderBy('created_at', 'desc'). You can override the column it uses by passing an argument - ->latest('updated_at')
The with method loads in the latest review.
The has method only queries photographers that have at least one item of the specified relationship
Have a look at Has Queries in Eloquent. If you want to customise the has query further, the whereHas method would be very useful
If you're interested
You can add query methods to the result of a relationship method. The relationship objects have a query builder object that they pass any methods that do not exist on themselves to, so you can use the relationships as a query builder for that relationship.
The advantage of adding query scopes / parameters within a relationship method on an Eloquent ORM model is that they are :
cacheable (see dynamic properties)
eager/lazy-loadable
has-queryable
What you need is best accomplished by a scoped query on your reviews relation.
Add this to your Review model:
use Illuminate\Database\Query\Builder;
use Illuminate\Database\Eloquent\Model;
class Review extends Model {
public function scopeLatest(Builder $query) {
// note: you can use the timestamp date for the last edited review,
// or use "id" instead. Both should work, but have different uses.
return $query->orderBy("updated_at", "desc")->first();
}
}
Then just query as such:
$photographers = Photographer::has("reviews");
foreach ($photographers as $photographer) {
var_dump($photographer->reviews()->latest());
}
Say I have two entities with about 20 properties per entity and a Many-to-Many relationship like so:
User (Id int,Name string, .......)
Issue (Id int,Name string, .......)
IssueAssignment (UserId,RoleId)
I want to create a new Issue and assign it to a number of existing Users. If I have code like so:
foreach(var userId in existingUserIds)
{
int id = userId
var user = _db.Users.First(r => r.Id == id);
issue.AssignedUsers.add(user);
}
_db.Users.AddObject(user);
_db.SaveChanges();
I noticed it seems terrribly inefficient when I run it against my SQL Database. If I look at
the SQL Profiler it's doing the following:
SELECT TOP(1) * FROM User WHERE UserId = userId
SELECT * FROM IssueAssignment ON User.Id = userId
INSERT INTO User ....
INSERT INTO IssueAssignment
My questions are:
(a) why do (1) and (2) have to happen at all?
(b) Both (1) and (2) bring back all fields do I need to do a object projection to limit the
fields, seems like unnecessary work too.
Thanks for the help
I have some possible clues for you:
This is how EF behaves. _db.Users is actaully a query and calling First on the query means executing the query in database.
I guess you are using EFv4 with T4 template and lazy loading is turned on. T4 templates create 'clever' objects which are able to fixup their navigation properties so once you add a User to an Issue it internally triggers fixup and tries to add the Issue to the User as well. This in turns triggers lazy loading of all issues related to the user.
So the trick is using dummy objects instead of real user. You know the id and you only want to create realtion between new issue and existing user. Try this (works with EFv4+ and POCOs):
foreach(var userId in existingUserIds)
{
var user = new User { Id = userId };
var _db.Users.Attach(user); // User with this Id mustn't be already loaded
issue.AssignedUsers.Add(user);
}
context.Issues.AddObject(issue);
context.SaveChanges();