[RFC] Simplify working with multiple languages

[karibertils]

I am finding myself wanting to support multiple languages without the headache that usually follows. And i came up with this.

Let's say i have this table

article table
--------------
id: int pk
title: text
body: text

Now i want to add multiple languages for title and body columns. Run couple of SQL commands.

ALTER TABLE article ALTER COLUMN title TYPE jsonb USING json_build_object('en_US', title);
ALTER TABLE article ALTER COLUMN body TYPE jsonb USING json_build_object('en_US', body);

Hack to get custom type into hasura

CREATE VIEW article_custom_type AS SELECT 0 as id, '' as title, '' as body;

Function using X-Hasura-Language to specify the language

CREATE FUNCTION article_with_language(hasura_session JSON) RETURNS SETOF article_custom_type
    STABLE
    LANGUAGE sql
AS
$$
 SELECT id, (article.title->>(hasura_session->>'x-hasura-language'))::TEXT, (article.body->>(hasura_session->>'x-hasura-language'))::TEXT
     FROM article;
$$;

Go to Hasura web gui and track view article_custom_type and function article_with_language using session data.

To insert articles

mutation {
  insert_article_one(object: {
    body: {
       en_US: "Example Body",
       is_IS: "Íslenskt dæmi"
    },
    title: {
       en_US: "Example Title",
       is_IS: "Íslenskur titill"
    }
  }) {
    id
  }
}

To query

query {
  article_with_language {
    id
    title
    body
  }
}

This works great. Having the query return standard types instead of json is really nice. But there are some issues with this approach.

• Every time when updating the schema for tables i will also have to update the custom view and function.
• Supporting multiple languages application wide will mean most tables will need this so alot of custom views and functions.
• The view hack for custom type is a bit ugly

If it was possible to easily "augment" specific columns like this that would be very be interesting and could probably solve other use cases as well.

Are there any standard practices for working with multiple languages in Hasura or things i'm missing that could prove useful ?

[karibertils]

After looking into computed fields. I can see they are a much better fit for doing this.

CREATE FUNCTION title_i18n(article_row article, hasura_session json)
RETURNS TEXT AS $$
  SELECT (article_row.title->>(hasura_session->>'x-hasura-language'))::TEXT
$$ LANGUAGE sql STABLE;

But you still need to create a new function for every table column that needs translation. Seems it's not possible to create some generic function that will handle many fields or tables ?

Another issue with the computed field is you cannot filter on them which works with the previous approach.

[karibertils]

This seems to be the best way to handle translations
#1824 (comment)