feat: persist ranked season rollovers

server/migrations/0001_initial.sql

@@ -112,6 +112,17 @@ CREATE TABLE seasons (
     rolled_over_at TIMESTAMPTZ
 );
 
+CREATE TABLE ranked_season_rollovers (
+    player_id TEXT NOT NULL REFERENCES identities(player_id),
+    season_id TEXT NOT NULL REFERENCES seasons(season_id),
+    rating DOUBLE PRECISION NOT NULL,
+    deviation DOUBLE PRECISION NOT NULL,
+    volatility DOUBLE PRECISION NOT NULL,
+    ranked_games INTEGER NOT NULL CHECK (ranked_games >= 0),
+    rolled_over_at TIMESTAMPTZ NOT NULL,
+    PRIMARY KEY (player_id, season_id)
+);
+
 CREATE TABLE penalties (
     penalty_id TEXT PRIMARY KEY,
     player_id TEXT NOT NULL REFERENCES identities(player_id),

server/migrations/test_migration.py

@@ -38,6 +38,8 @@ class MigrationTest(unittest.TestCase):
     def test_seasons_are_ranked_only_and_penalties_are_durable(self):
         self.assertIn("CHECK (playlist = 'ranked')", SQL)
         self.assertIn("CREATE TABLE penalties", SQL)
+        self.assertIn("CREATE TABLE ranked_season_rollovers", SQL)
+        self.assertIn("PRIMARY KEY (player_id, season_id)", SQL)
         self.assertIn("REFERENCES identities(player_id)", SQL)
         self.assertIn("REFERENCES matches(match_id)", SQL)
 

server/store/season_sql.go

@@ -0,0 +1,64 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"time"
+
+	"github.com/cosmic-clash/cosmic-clash/server/domain"
+)
+
+const SeasonRatingLockSQL = `SELECT player_id, rating, deviation, volatility, ranked_games, revision
+FROM ratings
+WHERE player_id = $1
+FOR UPDATE`
+
+const SeasonRolloverInsertSQL = `INSERT INTO ranked_season_rollovers
+    (player_id, season_id, rating, deviation, volatility, ranked_games, rolled_over_at)
+VALUES ($1, $2, $3, $4, $5, $6, $7)
+ON CONFLICT (player_id, season_id) DO NOTHING`
+
+const SeasonRatingUpdateSQL = `UPDATE ratings
+SET rating = $2, deviation = $3, volatility = $4, revision = revision + 1, updated_at = $5
+WHERE player_id = $1`
+
+// ApplyRankedSeasonRollover persists the domain rollover exactly once. The
+// marker insert and rating update share one SERIALIZABLE transaction, so a
+// retry after a worker failure cannot apply compression twice or leave a
+// marker without its corresponding rating snapshot.
+func ApplyRankedSeasonRollover(ctx context.Context, db *sql.DB, playerID, seasonID string, profile domain.RankedProfile, now time.Time) (domain.RankedProfile, bool, error) {
+	if playerID == "" {
+		return domain.RankedProfile{}, false, fmt.Errorf("player ID is required")
+	}
+	updated, _, err := domain.ApplySeasonRollover(profile, seasonID)
+	if err != nil {
+		return domain.RankedProfile{}, false, err
+	}
+	applied := false
+	err = RunSerializable(ctx, db, DefaultSerializableAttempts, func(ctx context.Context, tx *sql.Tx) error {
+		if _, err := tx.ExecContext(ctx, SeasonRatingLockSQL, playerID); err != nil {
+			return err
+		}
+		result, err := tx.ExecContext(ctx, SeasonRolloverInsertSQL, playerID, seasonID, updated.Value, updated.RD, updated.Volatility, updated.RankedGames, now)
+		if err != nil {
+			return err
+		}
+		changed, err := result.RowsAffected()
+		if err != nil {
+			return err
+		}
+		if changed == 0 {
+			return nil
+		}
+		if _, err := tx.ExecContext(ctx, SeasonRatingUpdateSQL, playerID, updated.Value, updated.RD, updated.Volatility, now); err != nil {
+			return err
+		}
+		applied = true
+		return nil
+	})
+	if err != nil {
+		return domain.RankedProfile{}, false, err
+	}
+	return updated, applied, nil
+}

server/store/serializable_test.go

@@ -19,7 +19,7 @@ func TestRetryableRecognisesPostgresSerializationAndDeadlockErrors(t *testing.T)
 }
 
 func TestClaimSQLContainsDurableOwnershipFences(t *testing.T) {
-	for _, fragment := range []string{"FOR UPDATE SKIP LOCKED", "state = 'QUEUED'", "proposal_participants", "revision = revision + 1", "INSERT INTO proposals"} {
+	for _, fragment := range []string{"FOR UPDATE SKIP LOCKED", "state = 'QUEUED'", "proposal_participants", "revision = revision + 1", "INSERT INTO proposals", "ranked_season_rollovers", "ON CONFLICT (player_id, season_id) DO NOTHING"} {
 		if !containsAnySQL(fragment) {
 			t.Fatalf("claim boundary missing %q", fragment)
 		}
@@ -27,7 +27,7 @@ func TestClaimSQLContainsDurableOwnershipFences(t *testing.T) {
 }
 
 func containsAnySQL(fragment string) bool {
-	return index(CandidateClaimSQL, fragment) >= 0 || index(ProposalParticipantInsertSQL, fragment) >= 0 || index(QueueTicketProposeSQL, fragment) >= 0 || index(ProposalInsertSQL, fragment) >= 0
+	return index(CandidateClaimSQL, fragment) >= 0 || index(ProposalParticipantInsertSQL, fragment) >= 0 || index(QueueTicketProposeSQL, fragment) >= 0 || index(ProposalInsertSQL, fragment) >= 0 || index(SeasonRolloverInsertSQL, fragment) >= 0
 }
 
 func index(s, fragment string) int {