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I'm using using entity reference, field collection , and field collection table modules on a site that features "courses" and "lessons" as content types. A field collection with unlimited values is embedded in the course content type, and it contains two fields: a text field for "section" and an entity reference field for "lesson". This allows the same lessons to be reused in different courses, while appearing under a different section. (see screen for reference).

This works pretty well, but performance when editing course nodes starts to degrade significantly after about 30 lessons are added to a course. At 100 lessons, it takes about 15 seconds to load a course for editing. With 140 lessons in a course, it takes about 22 seconds to edit a course node. I'm testing locally on a new D7 test site with devel-generated content.

Questions:

(1) Are there any obvious steps I should take to improve performance with field collections?

(2) As an alternative to field collections, would creating a compound field in code likely improve performance significantly?

(3) For testing performance generally, is there a simple profiling tool I can use with Drupal?

Example of a small course with 10 lessons added as field collections:

example of a small course with 10 lessons added as field collections

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  • As an alternative to field collections, would creating a compound field in code likely improve performance significantly? Always depends on how much data you have, but yes, almost certainly. If you have a field collection with 5 fields, that's at least 5 db queries (or joins, if you're lucky) to get the data. With a compound field that would be reduced to a single query
    – Clive ♦
    Commented Jan 8, 2014 at 16:33
  • Thanks for the input. It's kind of a daunting amount of code at first glance, but I guess it breaks down into smaller pieces that aren't too bad. I'll try to find time to give it a shot.
    – Dave Bruns
    Commented Jan 8, 2014 at 17:37
  • Yeah it can be a bit daunting, the field example module in Examples will be very useful if you decide to go down that route
    – Clive ♦
    Commented Jan 8, 2014 at 17:47
  • You are using the wrong tool for the job. Lessons should have a reference to courses, not the other way around. Use a custom entity type and kill field_collection.
    – Bojan Zivanovic
    Commented Jan 8, 2014 at 20:02
  • That's the way it is configured now on a production site. However, there is a new requirement to allow lessons to be re-used across multiple courses. Therefore, each course needs custom sections and its own sort order for lessons that belong to it. Any suggestions for how to approach?
    – Dave Bruns
    Commented Jan 8, 2014 at 20:06

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Update: In the end, I abandoned field collections and created a custom compound field that is attached to the 'course' content type.

This pretty much eliminated the performance problems. Opening a course node with 130 lessons in the field now takes 3-6 seconds, depending on the server.

And because the field is unlimited multivalue, the delta works a sorting mechanism for the lessons in views, etc.

I also added code to add more than one item at a time as seen here:

Slow "Add another item" with unlimited valued fields

When there are a lot of items in the field, adding a new item ends up taking a lot of time.

Good resources:

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