No autojoin setting for File & Image fields

[Toutouwai]

Short description of the issue

Not sure if this deliberate or an oversight, but there is no autojoin setting for File and Image fields.

Is there a reason why autojoin is not applicable to these fields? When using a page-per-image setup it seems like it would be desirable to enable autojoin on the image field because in virtually all cases where you get the page you are also going to want to get the image. As an example of when autojoin might make a difference, imagine outputting a large gallery of page-per-image images.

The FAQ post that introduced the feature says:

Not all fields have autojoin capability. You won't see the option listed on fields that don't have the capability.

But then it also says:

Be careful with multi-value fields that offer autojoin capability (page references and images, for example).

Which sounds like Image fields are supposed to have autojoin capability.

Setup/Environment

• ProcessWire version: 3.0.144

[ryancramerdesign]

@Toutouwai I think autojoin was allowed for file/image fields when that post was written, but later had to be removed. File/image fields can have a lot of data. There's an inherit limit on the number of bytes that can be autojoined in a single GROUP_CONCAT query, and it's a limit defined by a MySQL setting. You are likely to hit this limit on multi file/image fields, and I think it would confuse people, which is why the option is disabled. You aren't so likely to hit it on page reference fields, since it is just joining integers (page IDs), though I personally don't use autojoin on anything except title fields these days, as most of the time it's really not all that much of a performance benefit. Though if you'd like to experiment with it, try removing the getLoadQueryAutojoin() method from the /wire/modules/Fieldtype/FieldtypeFile.module class, and that should give you the option to enable autojoin for file/image fields.

[Toutouwai]

Thanks for the advice @ryancramerdesign.

Would you consider adding an option (maybe only visible when $config->advanced is true) that would allow autojoin to be enabled for File/Image fields? My current project is very image-focused and has a large number of images in a page-per-image setup. I think this is not that rare a scenario - for instance, @kongondo's Media Manager and Visual Page Selector modules are built to cater to this sort of setup. I think autojoin could be useful here, but any manual changes made to a core file will be lost the next time the core is upgraded.

[thetuningspoon]

Ryan, I've found autojoin to be indispensable in certain situations, mainly when looping through many pages and accessing fields on them, to generate tables, reports, etc. I am wondering if you can elaborate on the issue with using autojoin on multi-value page reference fields. I've observed that enabling autojoin on these fields results in faulty results. I think last time I tried it it only returned the first page from the set. Can you explain the technical issue here, and is it something that's possible to solve? If not, I really think it would be helpful to make it impossible to enable autojoin when a page reference field is multi value (both on the api and UI level) since it can lead to some head scratching bugs that are difficult to track down.