Improving joining of `RecordSet`s

[bowdi]

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Describe the problem to be solved

Refs:

• community #1495
• community #834

I've got a table similar to what is described in community #1495 , although in my scenario, I have the following schema:

Objectives

• type - choice e.g. project, task
• title - text field
• parent - a self reference to the objectives table as formula reference lists aren't supported as two way references these are included:
• links_from - a two way reference list
• links_to - the other two way reference list

Links

• from - reference field to objectives
• link - text explaining the link
• to - reference field to objectives
• links - a formula reference list joining the $from and $to fields as described in the community post

I have one use case that requires two joins, I'd like a reference list on Objectives that includes links of itself AND links of it's parent (chain). I would need to join links_from and links_to into a single reference list $links on Objectives first then join $parent.links and $links into $all_links together.

This is possible with nested list comprehension but it's not intuitive and could be simpler!

Describe the solution you would like

Overriding the __add__ operator in python record.RecordSet might work and it would result in formula like this:

• $links: $links_to + $links_from
• $all_links: $parent.links + $links

rather than this:

• $links: { el for sublist in [$links_to, $links_from] for el in sublist }
• $all_links: { el for sublist in [$parent.all_links, $links] for el in sublist }

[dsagal]

A couple of notes here:

One is that in addition to the list-comprehension approach, you can also use set($links_to) | set($links_from) (when you want to remove any duplicates and order doesn't natter) or list($links_to) + list($links_from (when you want to keep duplicates and order).

The other note is that a there was an improvement last year to a related issue reported here: https://github.com/gristlabs/grist-core/issues/1130. If adding an __add__ operator, it would make sense to match that behavior (which takes care of preserving order, but removing duplicates, see here).

[bowdi]

Oh nice! Thanks for those tips.

[raph-topo]

Thanks for the suggestions @dsagal. Might be worth adding to the Help Center's reference or cheat sheet.

Mentioning that, because of the name RecordSet, I though it inherited Python's set, but that isn't the case.