storing multidimensional array(matrix) rails postgresql

Question

I'm doing a rails application for a school project, and now i need store a matrix using postgresql. I was saving the values in an array, but i thought better and concluded that i need a matrix, but i don't know how to do this.

I tried in this way: - Migration:

add_column :table, :field, :text, array:true, default: []

Using this migration, the values are saving like:

[a,b,c,d,a,c,b,d,a,b,c,d,e]

I think what i need is like this:

[[a,b,c,d],[a,c,b,d],[a,b,c,d,e],[...]].

Because in this way the values are grouped.

Can someone help me?

I think this is duplicate check this answer: stackoverflow.com/questions/13314188/… also here is more info about blog.arkency.com/2014/10/… — Nezir
– Nezir, Commented Oct 2, 2018 at 18:25
@Nezir I checked the answer, and i think it's not what i need... I'm getting confused with the answers in the link — Bianca Longhi
– Bianca Longhi, Commented Oct 2, 2018 at 18:34
Can you please check this tutorial: blog.plataformatec.com.br/2014/07/rails-4-and-postgresql-arrays I didnt check info about multidimensional array but I hope this can be good starting point for you — Nezir
– Nezir, Commented Oct 2, 2018 at 18:59

Nezir · Accepted Answer · 2018-10-02 20:03:41Z

I made simple rails project to show you how to save multidimensional array to DB. Please check it here: https://github.com/nezirz/multidimensional_arrays

How it looks:

Here is super tutorial with informations you need. Please check this tutorial. This is a footer rule info about your case with multidimensional arrays:

One last note about arrays in PostgreSQL: there are no element count constraints, and any array can be multidimensional. With the multidimensional arrays, they must be “square” (the sub arrays must all have the same number of elements).

[[1,2,3], [2,3,4], [4,5,nil]]
# Valid array value in PostgreSQL, each subarray has the same number of
# elements
[1,2,[3,4]]
# Invalid array, we are mixing values and arrays at a single level

Please try this tutorial https://dockyard.com/blog/ruby/2012/09/18/rails-4-sneak-peek-postgresql-array-support

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