-- AppView database schema 0010: cursor for the local PDS firehose.
--
-- Why a second cursor table
--
-- The AppView now consumes two event streams, and they are numbered in
-- completely different spaces:
--
--   * `jetstream_cursor.cursor` is a Jetstream `time_us` — microseconds
--     since the epoch, produced by a public relay we do not control.
--   * this table's `cursor` is the `seq` of our own PDS's
--     `com.atproto.sync.subscribeRepos` — a small monotonic counter
--     that starts at 1 in a fresh PDS database.
--
-- Sharing one row between them would mean the larger of the two values
-- (always the Jetstream timestamp) permanently swallowing the other:
-- `cursor_advance` uses GREATEST, so the very first Jetstream event
-- would push the PDS cursor to ~1.7e15 and every subsequent
-- subscribeRepos connect would ask for a sequence the PDS will never
-- reach. Hence a table of its own, deliberately in the same shape as
-- `jetstream_cursor` so both read/advance the same way.
--
-- Shape
--   id          pinned to 1 by a CHECK — a single-row table, the same
--               pattern `jetstream_cursor` uses. It makes "advance the
--               cursor" a plain UPDATE with no upsert dance and makes a
--               second row impossible to create by accident.
--   cursor      the last `seq` we durably applied. 0 means "nothing
--               yet": the consumer then subscribes without a `cursor`
--               query parameter, which the PDS reads as "start from the
--               current head" rather than replaying the entire repo
--               history into a fresh index.
--   updated_at  observability only — how stale the stream is can be
--               read straight off the row.
--
-- The row is inserted here so `cursor_advance`'s UPDATE always has a
-- target; `pds_firehose::cursor_get` still tolerates a missing row and
-- returns 0.

CREATE TABLE pds_firehose_cursor (
    id             INTEGER PRIMARY KEY DEFAULT 1 CHECK (id = 1),
    cursor         BIGINT NOT NULL DEFAULT 0,
    updated_at     TIMESTAMPTZ NOT NULL DEFAULT now()
);
INSERT INTO pds_firehose_cursor (id, cursor) VALUES (1, 0);