fix: workshop models workshop sponsors with host query

[davidmillen50]

The previous implementation was loading workshops upfront which was causing slow queries which timed out the app. This new query should load only the related workshop sponsors to a workshop in one sql query

Benchmark times when running test file ./spec/features/chapter_spec.rb

Execution order when test file run	Old Code runtime (ms)	New SQL code runtime (ms)	Difference (ms)
1	15.21	2.789	12.421 faster
2	11.018	1.51	9.508 faster
3	12.304	2.964	9.34 faster
4	13.099	1.513	11.586 faster
5	12.886	1.609	11.277 faster
6	3.037	0.772	2.265 faster
7	11.072	2.705	8.367 faster
8	11.02	2.156	8.864 faster
9	11.155	2.122	9.033 faster
10	11.124	2.567	8.557 faster
11	10.757	1.92	8.837 faster
12	11.543	1.979	9.564 faster
13	11.976	2.921	9.055 faster
14	10.869	2.034	8.835 faster
15	10.614	1.998	8.616 faster
16	3.003	0.727	2.276 faster
17	3.016	0.842	2.174 faster
18	10.7	2.486	8.214 faster
19	10.771	1.987	8.784 faster
20	10.943	2.271	8.672 faster
21	2.597	0.705	1.892 faster
22	4.704	0.891	3.813 faster

[jonodrew]

Running this locally, the old code generates this SQL:

WorkshopSponsor Load (1.0ms)  SELECT "workshop_sponsors".* FROM "workshop_sponsors" WHERE (workshop_sponsors.host = TRUE) AND (workshop_sponsors.workshop_id = 1) ORDER BY "workshop_sponsors"."id" ASC LIMIT $1  [["LIMIT", 1]]
  Sponsor Load (0.6ms)  SELECT "sponsors".* FROM "sponsors" WHERE "sponsors"."id" = $1 ORDER BY updated_at desc LIMIT $2  [["id", 1], ["LIMIT", 1]]

while the new generates this:

  WorkshopSponsor Load (10.0ms)  SELECT "workshop_sponsors".* FROM "workshop_sponsors" WHERE "workshop_sponsors"."workshop_id" = $1 AND "workshop_sponsors"."host" = $2 ORDER BY "workshop_sponsors"."id" ASC LIMIT $3  [["workshop_id", 1], ["host", true], ["LIMIT", 1]]
  Sponsor Load (1.6ms)  SELECT "sponsors".* FROM "sponsors" WHERE "sponsors"."id" = $1 ORDER BY updated_at desc LIMIT $2  [["id", 1], ["LIMIT", 1]]

is that as expected?

[davidmillen50]

@jonodrew I'm trying a few things out still. Just about to push a change to use raw sql

[olleolleolle]

Not blocking a merge: this SQL query is expressible with ActiveRecord (see also Arel), but this change allows 1 query rather than more.