optimize stats using "materialized view"

sqlpage/migrations/001_schema.sql

@@ -0,0 +1,30 @@
+CREATE TABLE if not exists instances (
+  -- PK will be rowid
+    domain TEXT UNIQUE
+  , name TEXT
+  , slogan TEXT
+  , description TEXT
+  , languages TEXT
+  , open INT -- BOOLEAN
+  , version TEXT
+  , location TEXT  -- from IP
+  , failure INTEGER
+  , createdAt INTEGER  -- second since epoch
+  , updatedAt INTEGER  -- second since epoch
+)  strict;
+
+create table if not exists stats (
+    insertedAt INTEGER
+  , instance_id INTEGER  -- rowid of instance
+  , users INTEGER
+  , local_groups INTEGER
+  , total_groups INTEGER
+  , local_events INTEGER
+  , total_events INTEGER
+  , local_comments INTEGER
+  , total_comments INTEGER
+  , following INTEGER
+  , followers INTEGER
+  -- PK, would have been (instance_id, date)
+  -- to spare index, we declare no PK
+) strict;