-- Ported from the SQLite migration of the same number, and the only one that
-- is not a mechanical translation.
--
-- SQLite gets full-text search from an FTS5 virtual table with an external
-- content table and three triggers keeping it in step. PostgreSQL derives a
-- tsvector from the row itself, so there is nothing to keep in step and no
-- trigger to forget: the column cannot disagree with the row it is computed
-- from.
--
-- The search query differs too, and that difference lives in the Go code
-- rather than being hidden here — a query that means "match these words" is
-- spelled MATCH in one and @@ in the other, and pretending otherwise would
-- cost more than admitting it.

ALTER TABLE projects ADD COLUMN memory_retention_hours BIGINT;

CREATE TABLE memory_notes (
  id         BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  -- Scoped to a project and checked in SQL on every read, like threads.
  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
  -- A namespace inside the project, so two agents sharing a key do not read
  -- each other's notes.
  agent_id   TEXT NOT NULL,
  key        TEXT NOT NULL,
  text       TEXT NOT NULL,
  -- Normalised to ",a,b," so a tag matches whole, never as part of another.
  tags       TEXT NOT NULL DEFAULT '',
  created_at BIGINT NOT NULL,
  -- Touched on every write, so retention measures how long a note has gone
  -- unrefreshed rather than how old it is.
  updated_at BIGINT NOT NULL,
  -- 'simple' rather than a language configuration: these are an agent's own
  -- notes, in whatever language it chose, and stemming English rules over
  -- Turkish text would quietly stop finding things.
  search tsvector GENERATED ALWAYS AS (
    to_tsvector('simple', coalesce(key, '') || ' ' || coalesce(text, '') || ' ' || coalesce(tags, ''))
  ) STORED,
  UNIQUE (project_id, agent_id, key)
);
CREATE INDEX memory_notes_by_updated ON memory_notes(updated_at);
CREATE INDEX memory_notes_search ON memory_notes USING GIN (search);