diff --git a/app/logical/post_query_builder.rb b/app/logical/post_query_builder.rb
index 5f2dfd8ec..cc03c74ba 100644
--- a/app/logical/post_query_builder.rb
+++ b/app/logical/post_query_builder.rb
@@ -150,14 +150,17 @@ class PostQueryBuilder
       relation = relation.where("posts.is_deleted = FALSE")
     end
 
+    # The SourcePattern SQL function replaces Pixiv sources with "pixiv/[suffix]", where
+    # [suffix] is everything past the second-to-last slash in the URL.  It leaves non-Pixiv
+    # URLs unchanged.  This is to ease database load for Pixiv source searches.
     if q[:source]
       if q[:source] == "none%"
         relation = relation.where("(posts.source = '' OR posts.source IS NULL)")
-      elsif q[:source] =~ /pixiv/
-        raise ::Post::SearchError.new("pixiv source searches temporarily disabled")
+      elsif q[:source] =~ /^%\.?pixiv(\.net(\/img)?)?(%\/|(?=%$))(.+)$/
+        relation = relation.where("SourcePattern(posts.source) LIKE ? ESCAPE E'\\\\'", "pixiv/" + $5)
         has_constraints!
       else
-        relation = relation.where("posts.source LIKE ? ESCAPE E'\\\\'", q[:source])
+        relation = relation.where("SourcePattern(posts.source) LIKE SourcePattern(?) ESCAPE E'\\\\'", q[:source])
         has_constraints!
       end
     end
diff --git a/db/migrate/20130328092739_change_source_pattern_index_on_posts.rb b/db/migrate/20130328092739_change_source_pattern_index_on_posts.rb
new file mode 100644
index 000000000..523070ce0
--- /dev/null
+++ b/db/migrate/20130328092739_change_source_pattern_index_on_posts.rb
@@ -0,0 +1,24 @@
+class ChangeSourcePatternIndexOnPosts < ActiveRecord::Migration
+  def up
+    execute "set statement_timeout = 0"
+    execute "DROP INDEX index_posts_on_pixiv_suffix;"
+    execute "DROP INDEX index_posts_on_source_pattern;"
+    execute "CREATE FUNCTION SourcePattern(src text) RETURNS text AS $$
+               BEGIN
+                 RETURN regexp_replace(src, '^[^/]*(//)?[^/]*\.pixiv\.net/img.*(/[^/]*/[^/]*)$', 'pixiv\2');
+               END;
+             $$ LANGUAGE plpgsql IMMUTABLE RETURNS NULL ON NULL INPUT;"
+    execute "CREATE INDEX index_posts_on_source_pattern ON posts USING btree
+             ((SourcePattern(source)) text_pattern_ops);"
+  end
+
+  def down
+    execute "set statement_timeout = 0"
+    execute "DROP INDEX index_posts_on_source_pattern;"
+    execute "DROP FUNCTION SourcePattern(text);"
+    execute "CREATE INDEX index_posts_on_source_pattern ON posts USING btree
+             (source text_pattern_ops);"
+    execute "CREATE INDEX index_posts_on_pixiv_suffix ON posts USING btree
+             ((substring(source, 'pixiv.net/img.*/([^/]*/[^/]*)$')) text_pattern_ops);"
+  end
+end