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Avoid query from exists? on contradictory relation

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Co-authored-by: Adam Hess <HParker@github.com>
This commit is contained in:
John Hawthorn 2020-10-14 12:30:10 -07:00
parent c9357cd3e3
commit 3b622bc0d6
2 changed files with 13 additions and 0 deletions
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1
activerecord/lib/active_record/relation/finder_methods.rb
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@ -315,6 +315,7 @@ module ActiveRecord
end
relation = construct_relation_for_exists(conditions)
return false if relation.where_clause.contradiction?
skip_query_cache_if_necessary { connection.select_rows(relation.arel, "#{name} Exists?").size == 1 }
end

12
activerecord/test/cases/relation_test.rb
View file

@ -444,6 +444,18 @@ module ActiveRecord
end
end
test "no queries on empty relation exists?" do
assert_queries(0) do
Post.where(id: []).exists?(123)
end
end
test "no queries on empty condition exists?" do
assert_queries(0) do
Post.all.exists?(id: [])
end
end
private
def skip_if_sqlite3_version_includes_quoting_bug
if sqlite3_version_includes_quoting_bug?