Junction | Application/browser chooser | Dektop Application library

Sequelize does not support composite primary and foreign keys so you need to make id in Foo as the only unique key (ideally should be generated by DB) and so you will have a one foreign key column in FooBar per each table.

You need to use the Junction's parentColumn and entityColumn parameters e.g.

First you should amend the Dao's so that they return the id of the inserted row enabling you to ascertain the actual id of the inserted rows. So :-

This is happening because you are assigning the value in the if check. instead of assigning it using =, use == or === to check for equality

Coding DISTINCT will have no effect as for an @Relation what room does is build run it's own sub query to get ALL children of the parent.

However, with a few extra Dao's this can be achieved:-

First 2 queries (you may have the first already):-

I think the following mre⁽¹⁾ reproduces the multi-threading functionality required.

Each node (state / tile) is represented by an integer.
getTileNeighbors returns 3 random neighbors.
All thread share a synchronized visited collection, and should stop after target was added to visited.
(copy-paste the entire code to Main.java and run)

I don't know if what I'm trying to achieve is even possible, I couldn't find any example out there. Any suggestion?

It is possible. Perhaps consider the following.

When you associateBy you are saying that you are using an associative table to access the parent and children.

Such a table would have at least two columns, in your case one column to reference the stuffEntity and the other column to reference the relevant ThingEntity.

As such there are 4 columns involved in an @Relation with associateBy :-

• The Parent i.e. the @Embedded
• The Child(ren) i.e. the @Relation
• The column in the associative table that references the @Embedded
• The column in the associative table that references the @Relation

The first two are as per the parent and entity parameters of the @Relation, the second two are as per the 'Junction'.

Furthermore when including a hierarchy/levels there is a further complication, which you have encountered, is that the column to variable matching requires parent entity of the subordinate which is not in the subordinate. You need to specify the entity class as the respective entity NOT the class of the POJO being extracted.

So you could have something like :-

I have such a solution. And I'm surprised myself that I used two loops for!! Incredibly, I did it. First things first.

My proposal is based on a simplification. However, the mistake you will make at short distances will be relatively small. But the time gain is huge!

Well, I propose to count the distance in Cartesian coordinates, not spherical.

So we're going to need a simple function that computes the Cartesian coordinates based on the two arguments latitude and longitude. Here is our LatLong2Cart feature.

My first question is: is it correct how I created the "recipes_ingredients" table? Do I need the "id" or I can just have the two foreign keys "fk_recipe" and "fk_ingredient"?

Your junction table looks great! Your ID in recipes_ingredients will be auto numbered. I'd rename fk_recipe to recipe_id and fk_ingredient to ingredient_id, but it's totally fine to keep it the way you have it too. It's preference based.

And the second one is if it's possible to autopopulate the junction table when I insert a record in the other two tables. Or do I have to add manually every single association in the junction table?

Typically, you would manually enter ingredients that you don't already have in ingredients table, enter a new recipe name, and finally add entries in junction table.

However, if you have rules that say: All recipes containing the word pizza will have ingredient 1, 2 and 3, then you can create a stored procedure with logic to add information in the junctions table based on your rules. You can't cover all your use cases using a stored procedure, so you would still have to go to the junction table and add some entries manually.

Typically, web developers create a web page that allow such interaction of creating a recipe using a web page and then allowing selections of (or drag drop of) ingredients. In the background, the web page updates the junction table.