add support for read only post queries

app/controllers/posts_controller.rb

@@ -15,7 +15,7 @@ class PostsController < ApplicationController
     else
       limit = params[:limit] || (params[:tags] =~ /(?:^|\s)limit:(\d+)(?:$|\s)/ && $1) || CurrentUser.user.per_page
       @random = params[:random] || params[:tags] =~ /(?:^|\s)order:random(?:$|\s)/
-      @post_set = PostSets::Post.new(tag_query, params[:page], limit, raw: params[:raw], random: @random, format: params[:format])
+      @post_set = PostSets::Post.new(tag_query, params[:page], limit, raw: params[:raw], random: @random, format: params[:format], read_only: params[:ro])
       @posts = @post_set.posts
       respond_with(@posts) do |format|
         format.atom

app/logical/post_sets/post.rb

@@ -1,6 +1,6 @@
 module PostSets
   class Post < PostSets::Base
-    attr_reader :tag_array, :page, :per_page, :raw, :random, :post_count, :format
+    attr_reader :tag_array, :page, :per_page, :raw, :random, :post_count, :format, :read_only
 
     def initialize(tags, page = 1, per_page = nil, options = {})
       @tag_array = Tag.scan_query(tags)
@@ -10,6 +10,7 @@ module PostSets
       @raw = options[:raw].present?
       @random = options[:random].present?
       @format = options[:format] || "html"
+      @read_only = options[:read_only]
     end
 
     def tag_string
@@ -128,7 +129,7 @@ module PostSets
         elsif raw
           temp = ::Post.raw_tag_match(tag_string).order("posts.id DESC").paginate(page, :count => post_count, :limit => per_page)
         else
-          temp = ::Post.tag_match(tag_string).paginate(page, :count => post_count, :limit => per_page)
+          temp = ::Post.tag_match(tag_string, read_only).paginate(page, :count => post_count, :limit => per_page)
         end
         temp.each # hack to force rails to eager load
         temp

app/models/post.rb

@@ -1513,8 +1513,12 @@ class Post < ActiveRecord::Base
       where("posts.tag_index @@ to_tsquery('danbooru', E?)", tag.to_escaped_for_tsquery)
     end
 
-    def tag_match(query)
-      PostQueryBuilder.new(query).build
+    def tag_match(query, read_only = false)
+      if read_only
+        PostQueryBuilder.new(query).build(PostReadOnly.where("true"))
+      else
+        PostQueryBuilder.new(query).build
+      end
     end
 
     def positive

app/models/post_read_only.rb

@@ -0,0 +1,4 @@
+class PostReadOnly < Post
+  establish_connection "ro_#{Rails.env}".to_sym
+  attr_readonly *column_names
+end

script/install/database.yml.templ

@@ -20,3 +20,20 @@ production:
   database: danbooru2
   pool: 5
   timeout: 5000
+
+# read only databases, just point to local copies if you have no need
+ro_development:
+  adapter: postgresql
+  database: danbooru2
+
+ro_test:
+  adapter: postgresql
+  database: danbooru2_test
+
+ro_production:
+  adapter: postgresql
+  database: danbooru2
+
+ro_staging:
+  adapter: postgresql
+  database: danbooru2