Feeds generate n+1 queries for related image content

[ckinsey]

• Django Wagtail Feeds version: 0.1.0
• Python version: 3.6.5
• Operating System: Mac OSX 10.14

Description

Extended feeds executen+1 queries to gather image content from StreamFields.

What I Did

Here's a traced transaction from our APM tool:

I'm not sure what tools Wagtail provides for prefetching associated images from RichTextBlocks in StreamFields, but for large feeds this can generate 100s or 1000s of database queries to render a single feed.

Happy to spend some time on this and see if I can find a fix, but wanted to make sure I wasn't missing some easily configurable thing like subclassing the feed object overriding a queryset or something.

[chrisdev]

@ckinsey I think I'm the one that missed the performance hit! It was quick and dirty implementation that I had intended to get back too but I just did not have the time. We'll be grateful if you could take a look