db: build the comments count column

db/20180923004309-comment-count-build.sql

@@ -0,0 +1,10 @@
+-- Build the comments count column
+
+UPDATE pages
+SET commentCount = subquery.commentCount
+FROM (
+  SELECT COUNT(commentHex) as commentCount
+  FROM comments
+  WHERE state = 'approved'
+  GROUP BY (domain, path)
+) as subquery;