post_tags_match: replace joins with subqueries.

Refactor various post_tag_match methods to use subqueries instead of joins.

This simplifies things inside PostQueryBuilder, since now we can assume
we're always dealing with a Post relation, rather than some other table
joined with the posts table.

app/logical/post_query_builder.rb

@@ -1,8 +1,9 @@
 class PostQueryBuilder
-  attr_accessor :query_string
+  attr_accessor :query_string, :read_only
 
-  def initialize(query_string)
+  def initialize(query_string, read_only: false)
     @query_string = query_string
+    @read_only = read_only
   end
 
   def add_range_relation(arr, field, relation)
@@ -91,14 +92,12 @@ class PostQueryBuilder
     return CurrentUser.user.hide_deleted_posts?
   end
 
-  def build(relation = nil)
+  def build
     unless query_string.is_a?(Hash)
       q = Tag.parse_query(query_string)
     end
 
-    if relation.nil?
-      relation = Post.where("true")
-    end
+    relation = read_only ? PostReadOnly.all : Post.all
 
     if q[:tag_count].to_i > Danbooru.config.tag_query_limit
       raise ::Post::SearchError.new("You cannot search for more than #{Danbooru.config.tag_query_limit} tags at a time")

app/models/artist_commentary.rb

@@ -19,7 +19,7 @@ class ArtistCommentary < ApplicationRecord
     end
 
     def post_tags_match(query)
-      PostQueryBuilder.new(query).build(self.joins(:post)).reorder("")
+      where(post_id: PostQueryBuilder.new(query).build.reorder(""))
     end
 
     def deleted

app/models/comment.rb

@@ -52,7 +52,7 @@ class Comment < ApplicationRecord
     end
 
     def post_tags_match(query)
-      PostQueryBuilder.new(query).build(self.joins(:post)).reorder("")
+      where(post_id: PostQueryBuilder.new(query).build.reorder(""))
     end
 
     def for_creator(user_id)

app/models/note.rb

@@ -18,7 +18,7 @@ class Note < ApplicationRecord
     end
 
     def post_tags_match(query)
-      PostQueryBuilder.new(query).build(self.joins(:post)).reorder("")
+      where(post_id: PostQueryBuilder.new(query).build.reorder(""))
     end
 
     def for_creator(user_id)

app/models/post.rb

@@ -1662,7 +1662,7 @@ class Post < ApplicationRecord
 
       if read_only
         begin
-          PostQueryBuilder.new(query).build(PostReadOnly.where("true"))
+          PostQueryBuilder.new(query, read_only: true).build
         rescue PG::ConnectionBad
           PostQueryBuilder.new(query).build
         end

app/models/post_appeal.rb

@@ -11,7 +11,7 @@ class PostAppeal < ApplicationRecord
 
   module SearchMethods
     def post_tags_match(query)
-      PostQueryBuilder.new(query).build(self.joins(:post))
+      where(post_id: PostQueryBuilder.new(query).build.reorder(""))
     end
 
     def resolved

app/models/post_approval.rb

@@ -35,7 +35,7 @@ class PostApproval < ApplicationRecord
   concerning :SearchMethods do
     class_methods do
       def post_tags_match(query)
-        PostQueryBuilder.new(query).build(self.joins(:post))
+        where(post_id: PostQueryBuilder.new(query).build.reorder(""))
       end
 
       def search(params)

app/models/post_flag.rb

@@ -33,7 +33,7 @@ class PostFlag < ApplicationRecord
     end
 
     def post_tags_match(query)
-      PostQueryBuilder.new(query).build(self.joins(:post))
+      where(post_id: PostQueryBuilder.new(query).build.reorder(""))
     end
 
     def resolved

app/models/post_replacement.rb

@@ -21,7 +21,7 @@ class PostReplacement < ApplicationRecord
   concerning :Search do
     class_methods do
       def post_tags_match(query)
-        PostQueryBuilder.new(query).build(self.joins(:post))
+        where(post_id: PostQueryBuilder.new(query).build.reorder(""))
       end
 
       def search(params = {})

app/models/upload.rb

@@ -175,7 +175,7 @@ class Upload < ApplicationRecord
     end
 
     def post_tags_match(query)
-      PostQueryBuilder.new(query).build(self.joins(:post)).reorder("")
+      where(post_id: PostQueryBuilder.new(query).build.reorder(""))
     end
 
     def search(params)