add postarchive model, fixes #2831: Replace Subscriptions Link With Search:All Link

app/models/post_archive.rb

@@ -0,0 +1,49 @@
+class PostArchive < ActiveRecord::Base
+  def self.enabled?
+    Danbooru.config.aws_sqs_archives_url.present?
+  end
+
+  establish_connection "archive_#{Rails.env}".to_sym if enabled?
+  self.table_name = "post_versions"
+
+  def self.calculate_version(post_id, updated_at)
+    1 + PostVersion.where("post_id = ? and updated_at <= ?", post_id, updated_at).count
+  end
+
+  def self.export(version_id = 0)
+    PostVersion.where("id > version_id").find_each do |version|
+      previous = version.previous
+      tags = version.tags.scan(/\S+/)
+
+      if previous
+        added_tags = tags - previous.tags
+        removed_tags = previous.tags - tags
+      else
+        added_tags = tags
+        removed_tags = []
+      end
+
+      rating_changed = previous.nil? || version.rating != previous.try(:rating)
+      parent_changed = previous.nil? || version.parent_id != previous.try(:parent_id)
+      source_changed = previous.nil? || version.source != previous.try(:source)
+      create(
+        post_id: version.post_id,
+        tags: version.tags,
+        added_tags: added_tags,
+        removed_tags: removed_tags,
+        updater_id: version.updater_id],
+        updater_ip_addr: version.updater_ip_addr.to_s,
+        created_at: version.created_at,
+        updated_at: version.updated_at,
+        version: calculate_version(version.post_id, version.updated_at),
+        rating: version.rating,
+        rating_changed: rating_changed,
+        parent_id: version.parent_id,
+        parent_changed: parent_changed,
+        source: version.source,
+        source_changed: source_changed
+      )
+      puts "inserted #{version.id}"
+    end
+  end
+end