Support Updating Individual Array Elements

[philip-alldredge]

Problem Description

As far as I am aware, Diesel does not provide a mechanism for referencing individual array elements inside of the SQL queries.

What are you trying to accomplish?

Updating a single element in an array column when working with a Postgres database. I'd like to generate a query like:

UPDATE table_with_array
SET my_array[2] = 5.0;

Using syntax like:
update(table_with_array.set(my_array.index(1).eq(5.0)).execute(db_connection);

[sgrif]

This is a reasonable feature request, but isn't likely to get added in the near future. I'd recommend using sql_query for this.

[philip-alldredge]

Okay. Thanks! It's only a minor inconvenience. Everything else works great.

[sgrif]

Glad to hear it. 😄

[sgrif]

I actually don't think this would be super hard to implement if someone were interested in tackling it (being able to select a single element of an array would be a good first step). I think this might make sense as an issue for @galuhsahid or @yamishi13 in a few weeks.

[weiznich]

Just to write it somewhere:
I think this should be done in a similar manner like the implementation of numeric operations in diesel for various types. This means in detail that instead of providing a index method we should use the Index trait from the std-lib and then return a custom wrapper for codegen from there. (Just like for Add for example)

[sgrif]

@weiznich We cannot safely implement Index for this due to its signature.