-- Migration: 019_fix_chat_histories_fk
-- Fix the project_id foreign key on chat_histories to reference projects(guid)
-- instead of projects(id). This corrects the initial migration (018) which
-- used the wrong column — projects.id is a bigserial, projects.guid is the UUID.

ALTER TABLE chat_histories
    DROP CONSTRAINT IF EXISTS chat_histories_project_id_fkey;

ALTER TABLE chat_histories
    ADD CONSTRAINT chat_histories_project_id_fkey
    FOREIGN KEY (project_id) REFERENCES projects(guid) ON DELETE SET NULL;