修复了一点bug，然后增加了图层拆分更多的功能

backend/internal/postgres/layer_compositions_test.go

@@ -0,0 +1,75 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+
+	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/layercompositions"
+)
+
+func TestLayerCompositionAdapterScopesReadsAndUsesOptimisticSave(t *testing.T) {
+	now := time.Date(2026, 9, 2, 8, 0, 0, 0, time.UTC)
+	row := []any{"job-1", "owner", "base", true, []byte(`[{"id":"layer-1","assetId":"asset-1","name":"主体","visible":true,"box":[100,100,900,900],"rotation":0,"source":"provider"}]`), int64(2), now, now}
+	querier := &jobQuerier{rows: &jobRows{rows: [][]any{row}}}
+	database := NewDatabase(Config{Backend: BackendPostgres}, querier)
+
+	composition, found, err := database.FindLayerComposition(context.Background(), "owner", "job-1")
+	if err != nil || !found || composition.Version != 2 || len(composition.Layers) != 1 {
+		t.Fatalf("composition=%#v found=%v err=%v", composition, found, err)
+	}
+	if querier.query != FindLayerCompositionSQL || !reflect.DeepEqual(querier.args, []any{"owner", "job-1"}) {
+		t.Fatalf("query=%q args=%#v", querier.query, querier.args)
+	}
+
+	savedRow := append([]any(nil), row...)
+	savedRow[5] = int64(3)
+	querier.rows = &jobRows{rows: [][]any{savedRow}}
+	saved, err := database.SaveLayerComposition(context.Background(), layercompositions.Composition{
+		JobID: "job-1", OwnerID: "owner", BaseAssetID: "base", BaseVisible: true,
+		Layers: []layercompositions.Layer{{ID: "layer-1", AssetID: "asset-1", Name: "主体", Visible: true, Box: layercompositions.Box{100, 100, 900, 900}, Source: "provider"}},
+	}, 2)
+	if err != nil || saved.Version != 3 {
+		t.Fatalf("saved=%#v err=%v", saved, err)
+	}
+	if querier.query != SaveLayerCompositionSQL || len(querier.args) != 6 || querier.args[5] != int64(2) {
+		t.Fatalf("query=%q args=%#v", querier.query, querier.args)
+	}
+	for _, fragment := range []string{"WITH updated AS", "WHERE $6::bigint = 0", "version = seedream_layer_compositions.version + 1", "AND version = $6::bigint", "ON CONFLICT (job_id) DO NOTHING"} {
+		if !strings.Contains(SaveLayerCompositionSQL, fragment) {
+			t.Fatalf("upsert omits %q", fragment)
+		}
+	}
+}
+
+func TestLayerCompositionSaveSQLKeepsExistingVersionedUpdatesReachable(t *testing.T) {
+	// A top-level INSERT ... SELECT ... WHERE expectedVersion = 0 filters the
+	// source row before ON CONFLICT can run. In that shape every normal update
+	// (expectedVersion > 0) returns no row and is reported as a false conflict.
+	if strings.Contains(SaveLayerCompositionSQL, "SELECT $1::text, $2::text, $3::text, $4::boolean, $5::jsonb, 1, now(), now()\nWHERE $6::bigint = 0\nON CONFLICT") {
+		t.Fatal("versioned updates are unreachable because the INSERT source is filtered before ON CONFLICT")
+	}
+	for _, fragment := range []string{
+		"WITH updated AS",
+		"version = $6::bigint",
+		"$6::bigint > 0",
+		"WHERE $6::bigint = 0",
+		"UNION ALL",
+	} {
+		if !strings.Contains(SaveLayerCompositionSQL, fragment) {
+			t.Fatalf("save query does not preserve both update and create paths; missing %q", fragment)
+		}
+	}
+}
+
+func TestLayerCompositionAdapterReturnsConflictWhenVersionUpdateMatchesNoRow(t *testing.T) {
+	querier := &jobQuerier{rows: &jobRows{}}
+	database := NewDatabase(Config{Backend: BackendPostgres}, querier)
+	_, err := database.SaveLayerComposition(context.Background(), layercompositions.Composition{JobID: "job-1", OwnerID: "owner", BaseAssetID: "base", Layers: []layercompositions.Layer{}}, 4)
+	if !errors.Is(err, layercompositions.ErrConflict) {
+		t.Fatalf("err=%v", err)
+	}
+}