For example, if I wanted to do something like the following in MySQL query:
update foo set bar = bar + ?;
How would I achieve this using Bookshelf.js model?
I'm not exactly sure what you mean by atomic, perhaps transactions? You can do that in bookshelf, there's a whole section about it: http://bookshelfjs.org/#Bookshelf-transaction
However, if you're just trying to update a field, you can do that easily as follows:
var idStationIWantToUpdate = 1;
new Station({'id': idStationIWantToUpdate}).save({
route_name: 'my updated route name'
}).then(function(station) {
res.json(station.toJSON());
});
The important part is that you instantiate a model with the corresponding ID, then when you call save, it automatically updates the existing record.
I couldn't get this to work as I expect it, but there's an increment method in the knex query builder library (http://knexjs.org/#Builder-increment) which is the underlying engine for this functionality in bookshelf.js
What I ended up doing was:
foo.forge().save({bar:bookshelf.knex.raw('bar + 1')},{method:"update"});
Related
I'm currently working on saving data in a postgres DB using TypeORM with the NestJS integration. I'm saving data which keeps track of a version property using TypeORM's #VersionColumn feature, which increments a number each time save() is called on a repository.
For my feature it is important to check this version number before updating the records.
Important
I know I could technically achieve this by retrieving the record before updating it and checking the versions, but this leaves a small window for errors. If a 2nd user updates the same record in that millisecond between the get and save or if it would take longer for some weird reason, it would up the version and make the data in the first call invalid. TypeORM doesn't check the version value, so even if a call has a lower value than what is in the database, it still saves the data eventhough it should be seen as out of date.
1: User A checks latest version => TypeORM gives back the latest version: 1
2: User B updates record => TypeORM ups the version: 2
3: User A saves their data with version 1 <-- This needs to validate the versions first.
4: TypeORM overwrites User B's record with User A's data
What I'm looking for is a way to make TypeORM decline step 3 as the latest version in the database is 2 and User A tries to save with version 1.
I've tried using the querybuilder and update statements to make this work, but the build-in #VersionColumn only up the version on every save() call from a repository or entity manager.
Besides this I also got a tip to look into database triggers, but as far as I could find, this feature is not yet supported by TypeORM
Here is an example of the setup:
async update(entity: Foo): Promise<boolean> {
const value = await this._configurationRepository.save(entity);
if (value === entity) {
return true;
}
return false;
}
In my opinion, something like this is much better served through triggers directly in the Database as it will fix concerns around race conditions as well as making it so that modifications made outside the ORM will also update the version number. Here is a SQL Fiddle demonstrating triggers in action. You'll just need to incorporate it into your schema migrations.
Here is the relevant DDL from the SQL Fiddle example:
CREATE TABLE entity_1
(
id serial PRIMARY KEY,
some_value text,
version int NOT NULL DEFAULT 1
);
CREATE OR REPLACE FUNCTION increment_version() RETURNS TRIGGER AS
$BODY$
BEGIN
NEW.version = NEW.version + 1;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
CREATE TRIGGER increment_entity_1_version
BEFORE UPDATE
ON entity_1
FOR EACH ROW
EXECUTE PROCEDURE increment_version();
The same trigger function can be used for any table that has a version column in case this is a pattern you want to use across multiple tables.
I think you are looking for concurrency control. If this is the case there is a solution in this about 1/2 the way down. TypeORM concurrency control issue
Im using Objection.js as my ORM for a simple rainfall application. I need to be able to dynamically update and entry of one table when a lower level tables entires has been updated. To do this I need the whole entry I am updating so I can use that data to correctly update the dynamically updated entry.
Im using the $afterUpdate hook for the lower level table entry which. The issue I am having is that when I log this within the $afterUpdate hook function it only contains the properties for the parts of the entry I want to update. How can I get the entire entry? Im sure I could get the record by running an additional query to the DB but I was hoping there would be away to avoid this. Any help would be appreciated
I think, as of right now, you can only get the whole model with an extra query.
If you are doing the update with an instance query ($query) you can get the other properties from options.old.
Query:
const user = await User.query().findById(userId);
await user.$query()
.patch({ name: 'Tom Jane' })
Hook:
$afterUpdate(opt, queryContext) {
console.log(opt.old)
}
Patch
If you don't need to do this in the hook, you might want to use patch function chained with first().returning('*') to get the whole model in a single query, it's more efficient than patchAndFetchById in postgreSQL. Like stated in the documentation.
Because PostgreSQL (and some others) support returning('*') chaining, you can actually insert a row, or update / patch / delete (an) existing row(s), and receive the affected row(s) as Model instances in a single query, thus improving efficiency. See the examples for more clarity.
const jennifer = await Person
.query()
.patch({firstName: 'Jenn', lastName: 'Lawrence'})
.where('id', 1234)
.returning('*')
.first();
References:
http://vincit.github.io/objection.js/#postgresql-quot-returning-quot-tricks
https://github.com/Vincit/objection.js/issues/185
https://github.com/Vincit/objection.js/issues/695
I am working with SailsJs+MongoDB API. I have to create New colletion in mongoDB .Name of colletion will be in request Parameter.
example:
Suppose I want to create 'Users' collection in 'mongoDbDatabase' database
by following request.
{
"collectionName" : "Users",
"dbName" :"mongoDbDatabase"
}
Now is there any way to create dynamic collection in mongoDB using req.param('collectionName) variable ?
To use all the tools that Sails provides, you have to add code (before you start your app) for each Model / Collection you are planning to interact with. As a result, creating a collection dynamically will mean you can't take advantage of the whole data - framework sails provides.
Are you sure you need a dynamic collection? Why not a defined collection differentiated by attributes?
If you really need to do this from Sails, it looks like you can get access to the underlying raw mongo database:
var db = AnyModel.getDatastore().manager; // the database will be as defined in config/models.js or config/connections.js
var collectionName = 'Widgets';
db.createCollection(collectionName);
// note, even if this works, something like 'Widgets.find' will not.
I want to implement hashtags functionality with NodeJS and MongoDB support, so that I can also count the uses. Whenever a user adds hashtags to a page, I want to push or update them in the database. Each hastag looks like this:
{_id:<auto>, name:'hashtag_name', uses: 0}
The problem I'm facing is that the user can add new tags as well, so when he clicks 'done', I have to increment the 'uses' field for the existing tags, and add the new ones. The trick is how to do this with only one Mongo instruction? So far I thought of 2 possible ways of achieving this, but I'm not particularly happy with either:
Option 1
I have a service which fetches the existing tags from the db before the user starts to write a new article. Based on this, I can detect which tags are new, and run 2 queries: one which will add the new tags, and another which will update the existing one
Option 2
I will send the list of tags to the server, and there I will run a find() for every tag; if I found one, I'll update, if not, I'll create it.
Option 3 (without solution for now)
Best option would be to run a query which takes an array of tag names, do a $inc operation for the existing ones, and add the missing ones.
The question
Is there a better solution? Can I achieve the end result from option #3?
You should do something like this, all of them will be executed in one batch, this is only an snippet idea how to do it:
var db = new Db('DBName', new Server('localhost', 27017));
// Establish connection to db
db.open(function(err, db) {
// Get the collection
var col = db.collection('myCollection');
var batch = col.initializeUnorderedBulkOp();
for (var tag in hashTagList){
// Add all tags to be executed (inserted or updated)
batch.find({_id:tag.id}).upsert().updateOne({$inc: {uses:1}});
}
batch.execute(function(err, result) {
db.close();
});
});
I would use the Bulk method offered by Mongodb since version 2.6. In the same you could perform insertion operations when the tag is new and the counter update when it already exists.
I'm using Sequelize.js for ORM and have a few associations (which actually doesn't matter now). My models get get and set methods from those associations. Like this (from docs):
var User = sequelize.define('User', {/* ... */})
var Project = sequelize.define('Project', {/* ... */})
// One-way associations
Project.hasOne(User)
/*
...
Furthermore, Project.prototype will gain the methods getUser and setUser
according to the first parameter passed to define.
*/
So now, I have Project.getUser(), which returns a Promise. But if I call this twice on the very same object, I get SQL query executed twice.
My question is - am I missing something out, or this is an expected behavior? I actually don't want to make additional queries each time I call the same method on this object.
If this is expected - should I use custom getters with member variables which I manually populate and return if present? Or there is something more clever? :)
Update
As from DeBuGGeR's answer - I understand I can use includes when making a query in order to eager load everything, but I simply don't need it, and I can't do it all the time. It's waste of resources and a big overhead if I load my entire DB at the beginning, just to understand (by some criteria) that I won't need it. I want to make additional queries depending on situation. But I also can't afford to destroy all models (DAO objects) that I have and create new ones, with all the info inside them. I should be able to update parts of them, which are missing (from relations).
If you use getUser() it will make the query call, it dosent give you access to the user. You can manually save it to project.user or project.users depending on the association.
But you can try Eager Loading
Project.find({
include: [
{ model: User, as: 'user' } // here you HAVE to specify the same alias as you did in your association
]
}).success(function(project){
project.user // contains the user
});
Also e.g of getUser(). Dont expect it to automatically cache user and dont override this cleverly as it will create side effects. getUser is expected to get from database and it should!
Project.getUser().then(function(user){
// user is available and is a sequelize object
project.user = user; // save project.user and use it till u want to
})
The first part of things is clear - every call to get[Association] (for example Project.getUser()) WILL result in database query.
Sequelize does not maintain any kind of state nor cache for the results. You can get user in the Promisified result of the call, but if you want it again - you will have to make another query.
What #DeBuGGeR said - about using accessors is also not true - accessors are present only immediately after a query, and are not preserved.
As sometimes this is not ok, you have to implement some kind of caching system by yourself. Here comes the tricky part:
IF you want to use the same get method Project.getUser(), you won't be able to do it, as Sequelize overrides your instanceMethods. For example, if you have the association mentioned above, this won't work:
instanceMethods: {
getUser: function() {
// check if you have it, otherwise make a query
}
}
There are few possible ways to fix it - either change Sequelize core a little (to first check if the method exists), or use some kind of wrapper to those functions.
More details about this can be found here: https://github.com/sequelize/sequelize/issues/3707
Thanks to mickhansen for the cooperation on how to understand what to do :)