If I have a JSON object as follows
{
name: "John Smith",
tags: [1, 2, 3]
}
Each number in the tags array above is a foreign key associated with a Tag record.
What's the most efficient way of creating this record using sequelize?
Guessing your relations are like
Person.hasMany(Tag);
Tag.hasMany(Person);
You could create a Person and later on find those tasks and assign them to him
Person.create(obj)
.success(function (person) {
Tag.findAll({where: { id: obj.tags }})
.success(function (tags) {
person.setTags(tags);
});
});
Related
Is there a way to use include (which is actually a join table) to another Model, where the key is INSIDE a JSONB field? for example:
Item { id: INTEGER, someJsonbField: JSONB }
(item example: { id: 1, someJsonbField: { storeId: 2 } })
Then, for getting all of the items of store with id 2, you write something like this:
Item.findAll({ include: { model: 'Store', key: 'someJsonbField.storeId', ... } })
OFCOURSE, in a real world scenario, storeId should be inside Item directly, but only for the purpose of this question - How could it be done?
i'm having trouble with node & knex.js
I'm trying to build a mini blog, with posts & adding functionality to add multiple tags to post
I have a POST model with following properties:
id SERIAL PRIMARY KEY NOT NULL,
name TEXT,
Second I have Tags model that is used for storing tags:
id SERIAL PRIMARY KEY NOT NULL,
name TEXT
And I have many to many table: Post Tags that references post & tags:
id SERIAL PRIMARY KEY NOT NULL,
post_id INTEGER NOT NULL REFERENCES posts ON DELETE CASCADE,
tag_id INTEGER NOT NULL REFERENCES tags ON DELETE CASCADE
I have managed to insert tags, and create post with tags,
But when I want to fetch Post data with Tags attached to that post I'm having a trouble
Here is a problem:
const data = await knex.select('posts.name as postName', 'tags.name as tagName'
.from('posts')
.leftJoin('post_tags', 'posts.id', 'post_tags.post_id')
.leftJoin('tags', 'tags.id', 'post_tags.tag_id')
.where('posts.id', id)
Following query returns this result:
[
{
postName: 'Post 1',
tagName: 'Youtube',
},
{
postName: 'Post 1',
tagName: 'Funny',
}
]
But I want the result to be formated & returned like this:
{
postName: 'Post 1',
tagName: ['Youtube', 'Funny'],
}
Is that even possible with query or do I have to manually format data ?
One way of doing this is to use some kind of aggregate function. If you're using PostgreSQL:
const data = await knex.select('posts.name as postName', knex.raw('ARRAY_AGG (tags.name) tags'))
.from('posts')
.innerJoin('post_tags', 'posts.id', 'post_tags.post_id')
.innerJoin('tags', 'tags.id', 'post_tags.tag_id')
.where('posts.id', id)
.groupBy("postName")
.orderBy("postName")
.first();
->
{ postName: 'post1', tags: [ 'tag1', 'tag2', 'tag3' ] }
For MySQL:
const data = await knex.select('posts.name as postName', knex.raw('GROUP_CONCAT (tags.name) as tags'))
.from('posts')
.innerJoin('post_tags', 'posts.id', 'post_tags.post_id')
.innerJoin('tags', 'tags.id', 'post_tags.tag_id')
.where('posts.id', id)
.groupBy("postName")
.orderBy("postName")
.first()
.then(res => Object.assign(res, { tags: res.tags.split(',')}))
There are no arrays in MySQL, and GROUP_CONCAT will just concat all tags into a string, so we need to split them manually.
->
RowDataPacket { postName: 'post1', tags: [ 'tag1', 'tag2', 'tag3' ] }
The result is correct as that is how SQL works - it returns rows of data. SQL has no concept of returning anything other than a table (think CSV data or Excel spreadsheet).
There are some interesting things you can do with SQL that can convert the tags to strings that you concatenate together but that is not really what you want. Either way you will need to add a post-processing step.
With your current query you can simply do something like this:
function formatter (result) {
let set = {};
result.forEach(row => {
if (set[row.postName] === undefined) {
set[row.postName] = row;
set[row.postName].tagName = [set[row.postName].tagName];
}
else {
set[row.postName].tagName.push(row.tagName);
}
});
return Object.values(set);
}
// ...
query.then(formatter);
This shouldn't be slow as you're only looping through the results once.
I've two models - subscribers and tags
Sample data:
{
subscribers: [
{
name: "User 1",
tags: ["a","b"]
},
{
name: "User 2",
tags: ["c","d"]
}
]
}
I want to filter subscribers based on their tags.
If I give a and b tags, User 1 should list
If I give a and c tags,
both User 1 and User 2 should list
Here is what I tried:
Method 1:
tags is a column in subscribers model with array data type
/subscribers/?filter={"where":{"tags":{"inq":["a","b"]}}} // doesn't work
Method 2:
Created a separate table tags and set subscribers has many tags.
/subscribers/?filter={"where":{"tags":{"inq":["a","b"]}}} // doesn't work
How can I achieve this in Loopback without writing custom methods?
I've Postgresql as the connector
UPDATE
As mentioned in the loopback docs you should use inq not In
The inq operator checks whether the value of the specified property matches any of the values provided in an array. The general syntax is:
{where: { property: { inq: [val1, val2, ...]}}}
From this:
/subscribers/?filter={"where":{"tags":{"In":["a","b"]}}}
To this:
/subscribers/?filter={"where":{"tags":{"inq":["a","b"]}}}
Finally found a hack, using Regex! it's not a performant solution, but it works!!
{ "where": { "tags": { "regexp": "a|b" } } }
I have an object array in a reducer that looks like this:
[
{id:1, name:Mark, email:mark#email.com},
{id:2, name:Paul, email:paul#gmail.com},
{id:3,name:sally, email:sally#email.com}
]
Below is my reducer. So far, I can add a new object to the currentPeople reducer via the following:
const INITIAL_STATE = { currentPeople:[]};
export default function(state = INITIAL_STATE, action) {
switch (action.type) {
case ADD_PERSON:
return {...state, currentPeople: [ ...state.currentPeople, action.payload]};
}
return state;
}
But here is where I'm stuck. Can I UPDATE a person via the reducer using lodash?
If I sent an action payload that looked like this:
{id:1, name:Eric, email:Eric#email.com}
Would I be able to replace the object with the id of 1 with the new fields?
Yes you can absolutely update an object in an array like you want to. And you don't need to change your data structure if you don't want to. You could add a case like this to your reducer:
case UPDATE_PERSON:
return {
...state,
currentPeople: state.currentPeople.map(person => {
if (person.id === action.payload.id) {
return action.payload;
}
return person;
}),
};
This can be be shortened as well, using implicit returns and a ternary:
case UPDATE_PERSON:
return {
...state,
currentPeople: state.currentPeople.map(person => (person.id === action.payload.id) ? action.payload : person),
};
Mihir's idea about mapping your data to an object with normalizr is certainly a possibility and technically it'd be faster to update the user with the reference instead of doing the loop (after initial mapping was done). But if you want to keep your data structure, this approach will work.
Also, mapping like this is just one of many ways to update the object, and requires browser support for Array.prototype.map(). You could use lodash indexOf() to find the index of the user you want (this is nice because it breaks the loop when it succeeds instead of just continuing as the .map would do), once you have the index you could overwrite the object directly using it's index. Make sure you don't mutate the redux state though, you'll need to be working on a clone if you want to assign like this: clonedArray[foundIndex] = action.payload;.
This is a good candidate for data normalization. You can effectively replace your data with the new one, if you normalize the data before storing it in your state tree.
This example is straight from Normalizr.
[{
id: 1,
title: 'Some Article',
author: {
id: 1,
name: 'Dan'
}
}, {
id: 2,
title: 'Other Article',
author: {
id: 1,
name: 'Dan'
}
}]
Can be normalized this way-
{
result: [1, 2],
entities: {
articles: {
1: {
id: 1,
title: 'Some Article',
author: 1
},
2: {
id: 2,
title: 'Other Article',
author: 1
}
},
users: {
1: {
id: 1,
name: 'Dan'
}
}
}
}
What's the advantage of normalization?
You get to extract the exact part of your state tree that you want.
For instance- You have an array of objects containing information about the articles. If you want to select a particular object from that array, you'll have to iterate through entire array. Worst case is that the desired object is not present in the array. To overcome this, we normalize the data.
To normalize the data, store the unique identifiers of each object in a separate array. Let's call that array as results.
result: [1, 2, 3 ..]
And transform the array of objects into an object with keys as the id(See the second snippet). Call that object as entities.
Ultimately, to access the object with id 1, simply do this- entities.articles["1"].
If you want to replace the old data with new data, you can do this-
entities.articles["1"] = newObj;
Use native splice method of array:
/*Find item index using lodash*/
var index = _.indexOf(currentPeople, _.find(currentPeople, {id: 1}));
/*Replace item at index using splice*/
arr.splice(index, 1, {id:1, name:'Mark', email:'mark#email.com'});
mongoose scheme:
var restsSchema = new Schema({
name: String,
menu: mongoose.Schema.Types.Mixed
});
simplfied document:
{
name: "Dominos Pizza",
menu:{
"1":{
id: 1,
name: "Plain Pizza",
soldCounter: 0
},
"2":{
id: 2,
name: "Pizza with vegetables",
soldCounter: 0
}
}
}
I'm trying to update the soldCounter when given a single/array of "menu items" (such as "1" or "2" objects in the above document) as followed:
function(course, rest){
rest.markModified("menu.1");
db.model('rests').update({_id: rest._id},{$inc: {"menu.1.soldCounter":1}});
}
once this will work i obviously will want to make it more generic, something like: (this syntax is not working but demonstrate my needs)
function(course, rest){
rest.markModified("menu." + course.id);
db.model('rests').update({_id: rest._id},{$inc:{"menu.+"course.id"+.soldCounter":1}});
}
any one can help with this one?
I looked for an answer but couldn't find nothing regarding the 3rd level.
UPDATE:
Added id to the ducument's subDocument
I think you want add all ids into sub-document, one way you can do as following.
Rest.find({_id: rest._id}, function(err, o) {
// add all ids into sub-document...
Object.keys(o.menu).forEach(function(key) {
o.menu[key].id = key;
});
o.save(function(err){ ... });
});
It seems you want to operate the key in query, I am afraid you cannot do it in this way.
Please refer to the following questions.
Mongodb - regex match of keys for subobjects
MongoDB Query Help - query on values of any key in a sub-object