perf: select related objects in container queries

[pomegranited]

Description

Improves performance when fetching lots of container children / parents.

Supporting information

Part of:

• Publish section/subsection frontend-app-authoring#1977
• "Confirm Publish" Hierarchy Diagrams (Sidebar) frontend-app-authoring#1978

Blocks:

• feat: adds api to retrieve library block/container hierarchy [FC-0090] edx-platform#36813

Private-ref: FAL-4178

Testing instructions

See openedx/frontend-app-authoring#2186

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[bradenmacdonald]

In c971295 I have some further work on this branch that takes the queries of the main test in edx-platform down a bit further, from 225 to 196. But I'm not sure the added complexity is worth the cost. Many of these queries are just loading a single object, which are always going to be very fast queries anyways. We really want to focus on select_related where it's loading many rows of objects at once. This PR does include some of that though.

[pomegranited]

@bradenmacdonald

In c971295 I have some further work on this branch that takes the queries of the main test in edx-platform down a bit further, from 225 to 196. But I'm not sure the added complexity is worth the cost.

Yeah, I wasn't sure about muddying the API either.. I chose to continue adding things to the hard-coded select_related list instead, but am not sure if that's acceptable either. It did help a lot with the query counts on openedx/edx-platform#36813, as did avoiding using the content_libraries Metadata classes.

[bradenmacdonald]

This LGTM. I haven't tested it though.

[bradenmacdonald]

Do you think a single relationship is going to be sufficient here, or will we have some use cases where we need to specify multiple relationships to select, like ["containerversion__subsectionversion", "containerversion__unitversion"] ?

I'm guessing that since this is only loading a single level at a time, a single string like you have is sufficient.

[rpenido]

I'm guessing that since this is only loading a single level at a time, a single string like you have is sufficient.

I think that's the case for now. We can update it later (or move to something like what is discussed here: openedx/edx-platform#36813 (comment)).

[rpenido]

Hi @ormsbee! Sorry for the ping.
Could you review this again and check if we are good to merge?
Thanks!