Stash left_joins into joins to deduplicate redundant LEFT JOIN
#35864
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Originally the `JoinDependency` has the deduplication for eager loading (LEFT JOIN). This re-uses that deduplication for `left_joins`. And also, This makes left join order into part of joins, i.e.: Before: ``` association joins -> stash joins (eager loading, etc) -> string joins -> left joins ``` After: ``` association joins -> stash joins (eager loading, left joins, etc) -> string joins ``` Now string joins are able to refer left joins. Fixes rails#34325. Fixes rails#34332. Fixes rails#34536.
kamipo
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Apr 27, 2019
This fixes a regression for rails#35864. Usually, stashed joins (mainly eager loading) are performed as LEFT JOINs. But the case of merging joins/left_joins of different class, that (stashed) joins are performed as the same `join_type` as the parent context for now. Since rails#35864, both (joins/left_joins) stashed joins might be contained in `joins_values`, so each stashed joins should maintain its own `join_type` context. Fixes rails#36103.
kamipo
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May 19, 2019
…joins rails#36293 was an issue for through association with `joins` for a long time, but since rails#35864 through association with `left_joins` would also be affected by the issue. Implicit through table joins should be appeared before user supplied joins, otherwise loading through association with joins will cause a statement invalid error. Fixes rails#36293. ``` % ARCONN=postgresql bundle exec ruby -w -Itest test/cases/associations/has_many_through_associations_test .rb -n test_through_association_with_joins Using postgresql Run options: -n test_through_association_with_joins --seed 7116 # Running: E Error: HasManyThroughAssociationsTest#test_through_association_with_joins: ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR: missing FROM-clause entry for table "posts" LINE 1: ... "comments_posts" ON "comments_posts"."post_id" = "posts"."i... ^ : SELECT "comments".* FROM "comments" INNER JOIN "comments" "comments_posts" ON "comments_posts"."post_id" = "posts"."id" INNER JOIN "posts" ON "comments"."post_id" = "posts"."id" WHERE "posts"."author_id" = $1 rails test test/cases/associations/has_many_through_associations_test.rb:61 Finished in 0.388657s, 2.5730 runs/s, 0.0000 assertions/s. 1 runs, 0 assertions, 0 failures, 1 errors, 0 skips ```
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@kamipo Nice work! Any chance this will be back-ported to Rails 5.2? I'm unable to reference an automatically generated left join in a custom join now. Only solution I can think of for now is reverting the |
kamipo
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May 13, 2020
…associations rails#38597 is caused by rails#35864. To reproduce this issue, at least it is required four different models and three left joins from different relations. When merging a relation from different model, new stashed (left) joins should be placed before existing stashed joins, but rails#35864 had broken that expectation if left joins are stashed multiple times. This fixes that stashed left joins order as expected. Fixes rails#38597.
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@kreintjes I had to do To avoid redundantly joining. Not really an acceptable solution in some cases, but hopefully a workaround for some in lieu of an official patch. |
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Originally the
JoinDependencyhas the deduplication for eager loading(LEFT JOIN). This re-uses that deduplication for
left_joins.And also, This makes left join order into part of joins, i.e.:
Before:
After:
Now string joins are able to refer left joins.
Fixes #34325.
Fixes #34332.
Fixes #34536.