I am using https://github.com/ichikaway/cakephp-mongodb.git plugin for accessing mongodb datasource.
I have two Models: Teachers and Subject. I want joint find result on Teacher and Subject.
Here are my two models:
Teacher:
<?php
class Teacher extends AppModel {
public $actsAs = array('Containable');
public $hasOne = array('Subject');
public $primaryKey = '_id';
var $mongoSchema = array(
'name'=>array('type'=>'string'),
'age'=>array('type'=>'string'),
'subjectid'=>array('type'=>'string'),
'created'=>array('type'=>'datetime'),
'modified'=>array('type'=>'datetime'),
);
Subject:
<?php
class Subject extends Model {
public $actsAs = array('Containable');
public $belongsTo= array('Teacher');
public $primaryKey = '_id';
var $mongoSchema = array(
'name'=>array('type'=>'String'),
'code'=>array('type'=>'String'),
'created'=>array('type'=>'datetime'),
'modified'=>array('type'=>'datetime')
);
In Teachers Controller to get joint result, I did:
$results = $this->Teacher->find('all',array('contain'=>array('Subject')));
$this->set('results', $results);
But I am not getting any result from Subjects Collections.
Here is what I am getting:
array(5) {
[0]=>
array(1) {
["Teacher"]=>
array(7) {
["_id"]=>
string(24) "52e63d98aca7b9ca2f09d869"
["name"]=>
string(13) "Jon Doe"
["age"]=>
string(2) "51"
["subjectid"]=>
string(24) "52e63c0faca7b9272c09d869"
["modified"]=>
object(MongoDate)#78 (2) {
["sec"]=>
int(1390820760)
["usec"]=>
int(392000)
}
["created"]=>
object(MongoDate)#79 (2) {
["sec"]=>
int(1390820760)
["usec"]=>
int(392000)
}
}
}
I am a cakephp/mongoDB rookie only, Please guide me to get the desired result.
Edit: I read that mongoDb don't support Join Operation. Then How to manually do it? I mean I can write two find query on each Model, then how to combine both array and set it to view?
As you said, MongoDB does not support joins. Documents in query results come directly from the collection being queried.
In this case, I imagine you would query for Teacher documents and then iterate over all documents and query for the Subject documents by the subjectid field, storing the resulting subject document in a new property on the Teacher. I'm not familiar with this CakePHP module, but you may or may not need to wrap the subjectid string value in a MongoId object before querying. This depends on whether or not your document _id fields in MongoDB are ObjectIds or plain strings.
If Subjects only belong to a single teacher and you find that you never query for Subjects outside of the context of a Teacher, you may want to consider embedding the Subject instead of simply storing its identifier. That would remove the need to query for Subjects after the fact.
Related
I have an issue where we create a complex IQueryable that we need to make it more efficient.
There are 2 tables that should only be included if columns from them are being filtered.
My exact situation is complex to explain so I thought I could illustrate it with an example for cars.
If I have a CarFilter class like this:
public class CarFilter
{
public string BrandName { get;set; }
public decimal SalePrice {get; set; }
}
Let's say that we have a query for car sales:
var info = from car in cars
from carSale in carSales on carSale.BrandId == car.BrandId && car.ModelId == carSale.ModelId
from brand in carBrands on car.BrandId == brand.BrandId
select car
var cars = info.ToList();
Let's say that this is a huge query that returns 100'000 rows as we are looking at cars and sales and the associated brands.
The user only wants to see the details from car, the other 2 tables are for filtering purposes.
So if the user only wants to see Ford cars, our logic above is not efficient. We are joining in the huge car sale table for no reason as well as CarBrand as the user doesn't care about anything in there.
My question is how can I only include tables in my IQueryable if they are actually needed?
So if there is a BrandName in my filter I would include CarBrand table, if not, it's not included.
Using this example, the only time I would ever want both tables is if the user specified both a BrandName and SalePrice.
The semantics are not important here, i.e the number of records returned being impacted by the joins etc, I am looking for help on the approach
I am using EF Core
Paul
It is common for complex filtering. Just join when it is needed.
var query = cars;
if (filter.SalePrice > 0)
{
query =
from car in query
join carSale in carSales on new { car.BrandId, car.ModelId } equals new { carSale.BrandId, carSale.ModelId }
where carSale.Price >= filter.SalePrice
select car;
}
if (!filter.BrandName.IsNullOrEempty())
{
query =
from car in query
join brand in carBrands on car.BrandId equals brand.BrandId
where brand.Name == filter.BrandName
select car;
}
var result = query.ToList();
I'm using GORM for MongoDB in my Grails 3 web-app to manage read/writes from DB.
I have the following 2 domain classes:
class Company {
String id
}
class Team {
String id
Company company
}
For teams, their company is saved on DB as String, and with GORM I can simply use team.company to get an instance of Company domain class.
However, I need to override the getter for company, and I need the raw value for company id (as stored on DB), without GORM getting in the way and performing its magic.
Is there a way to get the raw String value?
Any help is welcome! Thanks in advance
Update (May 27)
Investigating #TaiwaneseDavidCheng suggestion, I updated my code to
class Company {
String id
}
class Team {
String id
Company company
String companyId
static mapping = {
company attr: "company" // optional
companyId attr: "company", insertable: false, updateable: false
}
}
Please note that I'm using GORM for MongoDB, which (citing the manual) tries to be as compatible as possible with GORM for Hibernate, but requires a slightly different implementation.
However I found out (by trial&error) that GORM for MongoDB doesn't support a similar solution, as it seems only one property at a time can be mapped to a MongoDB document property.
In particular the last property in alphabetical order wins, e.g. companyId in my example.
I figured out a way to make the whole thing work, I'm posting my own answer below.
given a non-insertable non-updateable column "companyId" in domain class
class Company {
String id
}
class Team {
String id
Company company
Long companyId
static mapping = {
company column:"companyId"
companyId column:"companyId",insertable: false,updateable: false
}
}
(Follows the edit to my question above)
I defined a custom mapping, and made use of Grails transients by also defining custom getter and setter for team's company.
class Company {
String id
}
class Team {
String id
Company company
String companyId
static mapping = {
companyId attr: "company" // match against MongoDB property
}
static transients = [ 'company' ] // non-persistent property
Company getCompany() {
return Company.get(companyId)
}
void setCompany(Company company) {
companyId = company.id
}
}
I have an authors collection that has a many-to-many relation to a posts collection. The posts collection has a category field which can be, for example, "Suspense", "Drama", "Action", etc.
I need to go through my entire posts collection and group by the category fields and also have the associated counts.
This is what I have so far:
$authors = Author::where('active', true)->get();
foreach ($authors as $author){
foreach ($author->posts()->groupBy('category')->get() as $data){
// Do some logic
}
}
Basically the output I am expecting is an array with category as keys and the counts as a value. So if I do $a['Drama'] it gives me count of how many times that author wrote a post with that category.
I can probably figure it out by working in my loop logic above but it does not look very efficient. Should I look at aggregation? If so can someone get me started?
Try this:
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
$authors = DB::collection('authors')
->where('active', true)
->get();
// Laravel >= 5.3 would return collection instead of plain array
$authors = is_array($authors) ? Collection::make($authors) : $authors;
$authors->map(function ($author) {
return $author
->posts()
->groupBy('category')
->get()
->map(function ($collection) {
return $collection->count();
});
});
I have three tables:
categories
id, title
products
id, name
categories_products
id, category_id, product_id
I have also setup the according models and relationships (both have belongsToMany of the other)
Now I want to get all products belonging to a category
Category::where('title','Electronics')->first()->products()->limit(10)->get(['products.name']);
which works fine, but I also want to include the category title for each product as well:
Category::where('title','Electronics')->first()->products()->limit(10)->get(['products.name','category.title']);
However it returns: Column not found category.title
I thought that the relation would take care of it.
EDIT: Models -->
Category:
class Category extends Model
{
protected $fillable = array('title');
public function products()
{
return $this->belongsToMany('Product', 'categories_products', 'category_id', 'product_id');
}
}
class Product extends Model
{
protected $fillable = array('name');
public function categories()
{
return $this->belongsToMany('Category', 'categories_products', 'product_id', 'category_id');
}
}
The reason you're getting the error is because get() works just like select() and because you're running the category query and then running the product query after there is no categories table to reference for the select.
Look into Eager Loading. It will help with a lot of these kinds of issues. Your query can be written as:
Product::select('id', 'name')
->with(['categories' => function($query) {
return $query->select('id', 'title');
}])
->whereHas('categories', function($query) {
return $query->where('title', 'Electronics');
})
->limit(10)
->get();
Because we are lazy loading you NEED the id column on each model so Laravel knows where to attach the relationships after the queries are run.
The with() method above will eager load the categories relationship and the whereHas() method puts a relationship constraint on the current query.
UPDATE
Similar query from Category model:
$category = Category::where('title','Electronics')
->with(['products' => function($query) {
return $query->select('id', 'name')->limit(10);
}])
->first(['id', 'title']);
Then access the products with:
$category->products
I need to query a collection based on a list of parameters.
For example my model is:
public class Product
{
string id{get;set;}
string title{get;set;}
List<string> tags{get;set;}
DateTime createDate{get;set;}
DbReference<User> owner{get;set;}
}
public class User
{
string id{get;set;}
...other properties...
}
I need to query for all products owned by specified users and sorted by creationDate.
For example:
GetProducts(List<string> ownerIDs)
{
//query
}
I need to do it in one query if possible not inside foreach. I can change my model if needed
It sounds like you are looking for the $in identifier. You could query products like so:
db.product.find({owner.$id: {$in: [ownerId1, ownerId2, ownerId3] }}).sort({createDate:1});
Just replace that javascript array [ownerId1, ...] with your own array of owners.
As a note: I would guess this query is not very efficient. I haven't had much luck with DBRefs in MongoDB, which essentially adds relations to a non-relational database. I would suggest simply storing the ownerID directly in the product object and querying based on that.
The solution using LINQ is making an array of user IDs and then do .Contains on them like that:
List<string> users = new List<string>();
foreach (User item in ProductUsers)
users .Add(item.id);
return MongoSession.Select<Product>(p => users .Contains(p.owner.id))
.OrderByDescending(p => p.createDate)
.ToList();