FIX: Revert recursively tag lookup with missing ancestor tags (#18439)

This reverts commit 049f8569d8.

To be revisited with a more comprehensive solution covering parent
selection when multiple parents exist.

lib/discourse_tagging.rb

@@ -13,29 +13,6 @@ module DiscourseTagging
           ON tgm.tag_group_id = tg.id
   SQL
 
-  ANCESTOR_TAG_IDS_SQL ||= <<~SQL
-    WITH RECURSIVE ancestors AS (
-      SELECT
-        tgm.tag_id,
-        tg.parent_tag_id
-      FROM
-        tag_group_memberships tgm
-        INNER JOIN tag_groups tg ON tg.id = tgm.tag_group_id
-      WHERE
-        tg.parent_tag_id IS NOT NULL
-        AND tgm.tag_id IN (:tag_ids)
-      UNION
-      SELECT
-        tgm.tag_id,
-        tg.parent_tag_id
-      FROM
-        tag_group_memberships tgm
-        INNER JOIN tag_groups tg ON tg.id = tgm.tag_group_id
-        INNER JOIN ancestors ON tgm.tag_id = ancestors.parent_tag_id
-    )
-    SELECT * FROM ancestors
-  SQL
-
   def self.tag_topic_by_names(topic, guardian, tag_names_arg, append: false)
     if guardian.can_tag?(topic)
       tag_names = DiscourseTagging.tags_for_saving(tag_names_arg, guardian) || []
@@ -116,7 +93,14 @@ module DiscourseTagging
         # add missing mandatory parent tags
         tag_ids = tags.map(&:id)
 
-        parent_tags_map = DB.query(ANCESTOR_TAG_IDS_SQL, tag_ids: tag_ids).inject({}) do |h, v|
+        parent_tags_map = DB.query("
+          SELECT tgm.tag_id, tg.parent_tag_id
+            FROM tag_groups tg
+          INNER JOIN tag_group_memberships tgm
+              ON tgm.tag_group_id = tg.id
+           WHERE tg.parent_tag_id IS NOT NULL
+             AND tgm.tag_id IN (?)
+        ", tag_ids).inject({}) do |h, v|
           h[v.tag_id] ||= []
           h[v.tag_id] << v.parent_tag_id
           h

spec/lib/discourse_tagging_spec.rb

@@ -497,19 +497,9 @@ RSpec.describe DiscourseTagging do
       end
 
       it "adds all parent tags that are missing" do
-        parent_tag_group = Fabricate(:tag_group)
         parent_tag = Fabricate(:tag, name: 'parent')
-        parent_tag_group.tags = [parent_tag]
-
         tag_group2 = Fabricate(:tag_group, parent_tag_id: parent_tag.id)
         tag_group2.tags = [tag2]
-
-        tag_group1 = Fabricate(:tag_group)
-        tag_group1.tags = [tag1]
-
-        tag_group3 = Fabricate(:tag_group, parent_tag_id: tag1.id)
-        tag_group3.tags = [tag3]
-
         valid = DiscourseTagging.tag_topic_by_names(topic, Guardian.new(user), [tag3.name, tag2.name])
         expect(valid).to eq(true)
         expect(topic.reload.tags.map(&:name)).to contain_exactly(
@@ -529,49 +519,6 @@ RSpec.describe DiscourseTagging do
         expect(valid).to eq(true)
         expect(topic.reload.tags.map(&:name)).to contain_exactly(*[parent_tag, common].map(&:name))
       end
-
-      context "when tag group has grandparents" do
-        let(:tag_group1) { Fabricate(:tag_group) }
-        let(:foo) { Fabricate(:tag, name: 'foo') }
-        let(:tag_group2) { Fabricate(:tag_group, parent_tag_id: foo.id) }
-        let(:bar) { Fabricate(:tag, name: 'bar') }
-        let(:tag_group3) { Fabricate(:tag_group, parent_tag_id: bar.id) }
-        let(:baz) { Fabricate(:tag, name: 'baz') }
-
-        before do
-          tag_group1.tags = [foo]
-          tag_group2.tags = [bar]
-          tag_group3.tags = [baz]
-        end
-
-        it "recursively adds all ancestors" do
-          valid = DiscourseTagging.tag_topic_by_names(topic, Guardian.new(user), [baz.name])
-          expect(valid).to eq(true)
-          expect(topic.reload.tags.map(&:name)).to contain_exactly(*[foo, bar, baz].map(&:name))
-        end
-
-        it "adds only one parent when multiple parents exist" do
-          alt_parent_group = Fabricate(:tag_group)
-          alt = Fabricate(:tag, name: 'alt')
-          alt_parent_group.tags = [alt]
-
-          alt_baz_group = Fabricate(:tag_group, parent_tag_id: alt.id)
-          alt_baz_group.tags = [baz]
-
-          valid = DiscourseTagging.tag_topic_by_names(topic, Guardian.new(user), [baz.name])
-          expect(valid).to eq(true)
-          expect(topic.reload.tags.map(&:name)).to contain_exactly(*[foo, bar, baz].map(&:name))
-        end
-
-        it "adds missing tags even with cycles" do
-          tag_group4 = Fabricate(:tag_group, parent_tag_id: baz.id)
-          tag_group4.tags = [foo]
-
-          valid = DiscourseTagging.tag_topic_by_names(topic, Guardian.new(user), [baz.name])
-          expect(valid).to eq(true)
-          expect(topic.reload.tags.map(&:name)).to contain_exactly(*[foo, bar, baz].map(&:name))
-        end
-      end
     end
 
     context "when enforcing required tags from a tag group" do