feat(server): the review log, synced and append-only

ReviewLog keeps every rating of a card: the card, the rating (FSRS's 1 again to 4 easy), when (UTC) and how long answering took, as decided. It is never changed; each device derives a card's schedule by replaying its reviews, so reviews from different devices never conflict. No device id: the sync engine knows each row's device.

The migration (by CLI) only adds: the table, an index on spaceId for space deletion, one for a card's reviews in time order, and the foreign keys (from the space with ON DELETE CASCADE; from the card with ON DELETE CASCADE, DEFERRABLE INITIALLY DEFERRED).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_server/migrations/20260930145136285-reviews/migration.sql

@@ -0,0 +1,107 @@
+BEGIN;
+
+--
+-- Function: gen_random_uuid_v7()
+-- Source: https://gist.github.com/kjmph/5bd772b2c2df145aa645b837da7eca74
+-- License: MIT (copyright notice included on the generator source code).
+--
+create or replace function gen_random_uuid_v7()
+returns uuid
+as $$
+begin
+  -- use random v4 uuid as starting point (which has the same variant we need)
+  -- then overlay timestamp
+  -- then set version 7 by flipping the 2 and 1 bit in the version 4 string
+  return encode(
+    set_bit(
+      set_bit(
+        overlay(uuid_send(gen_random_uuid())
+                placing substring(int8send(floor(extract(epoch from clock_timestamp()) * 1000)::bigint) from 3)
+                from 1 for 6
+        ),
+        52, 1
+      ),
+      53, 1
+    ),
+    'hex')::uuid;
+end
+$$
+language plpgsql
+volatile;
+
+--
+-- ACTION CREATE TABLE
+--
+CREATE TABLE "review_log" (
+    "id" uuid PRIMARY KEY DEFAULT gen_random_uuid_v7(),
+    "spaceId" bigint,
+    "cardId" uuid NOT NULL,
+    "rating" bigint NOT NULL,
+    "reviewedAt" timestamp without time zone NOT NULL,
+    "durationMs" bigint NOT NULL
+);
+
+-- Indexes
+CREATE INDEX "review_log_space_idx" ON "review_log" USING btree ("spaceId");
+CREATE INDEX "review_log_card_idx" ON "review_log" USING btree ("cardId", "reviewedAt");
+
+--
+-- ACTION CREATE FOREIGN KEY
+--
+ALTER TABLE ONLY "review_log"
+    ADD CONSTRAINT "review_log_fk_0"
+    FOREIGN KEY("spaceId")
+    REFERENCES "offline_sync_spaces"("id")
+    ON DELETE CASCADE
+    ON UPDATE NO ACTION;
+ALTER TABLE ONLY "review_log"
+    ADD CONSTRAINT "review_log_fk_1"
+    FOREIGN KEY("cardId")
+    REFERENCES "card"("id")
+    ON DELETE CASCADE
+    ON UPDATE NO ACTION
+    DEFERRABLE INITIALLY DEFERRED;
+
+
+--
+-- MIGRATION VERSION FOR halkyon_learn
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('halkyon_learn', '20260930145136285-reviews', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260930145136285-reviews', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod', '20260824182259319', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260824182259319', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod_auth_idp
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod_auth_idp', '20260924105404509', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260924105404509', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod_offline_sync
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod_offline_sync', '20260914143806119', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260914143806119', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod_auth_core
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod_auth_core', '20260924105232991', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260924105232991', "timestamp" = now();
+
+
+COMMIT;