Too many refactors in one:

- Allowed adding ephemeral(ish) views and functions
- Moved message_count to a concrete database field
- Moved most proxy logic to a stored procedure
- Moved database files around and refactored schema manager

PluralKit.Core/Database/Migrations/7.sql

@@ -0,0 +1,33 @@
+-- SCHEMA VERSION 7: 2020-06-12
+-- (in-db message count row)
+
+-- Add message count row to members table, initialize it with the correct data
+alter table members add column message_count int not null default 0;
+update members set message_count = (select count(*) from messages where messages.member = members.id);
+
+
+-- Create a trigger function to increment the message count on inserting to the messages table
+create function trg_msgcount_increment() returns trigger as $$
+begin
+    update members set message_count = message_count + 1 where id = NEW.member;
+    return NEW;
+end;
+$$ language plpgsql;
+
+create trigger increment_member_message_count before insert on messages for each row execute procedure trg_msgcount_increment();
+
+
+-- Create a trigger function to decrement the message count on deleting from the messages table
+create function trg_msgcount_decrement() returns trigger as $$
+begin
+    -- Don't decrement if count <= zero (shouldn't happen, but we don't want negative message counts)
+    update members set message_count = message_count - 1 where id = OLD.member and message_count > 0;
+    return OLD;
+end;
+$$ language plpgsql;
+
+create trigger decrement_member_message_count before delete on messages for each row execute procedure trg_msgcount_decrement();
+
+
+-- (update schema ver)
+update info set schema_version = 7;