fix migration down; check for greater forkIDs instead of the next +1

db/migrations/state/0009.sql

@@ -2,6 +2,8 @@
 ALTER TABLE IF EXISTS state.fork_id DROP CONSTRAINT IF EXISTS fork_id_block_num_fkey;
 
 -- +migrate Down
+DELETE FROM state.fork_id f
+ WHERE NOT EXISTS(SELECT 1 FROM state.block b WHERE b.block_num = f.block_num);
+
 ALTER TABLE IF EXISTS state.fork_id ADD CONSTRAINT fork_id_block_num_fkey
-FOREIGN KEY(block_num)
-REFERENCES state.block (block_num) ON DELETE CASCADE;
+FOREIGN KEY(block_num) REFERENCES state.block (block_num) ON DELETE CASCADE;

state/pgstatestorage/forkid.go

@@ -81,9 +81,11 @@ func (p *PostgresStorage) AddForkIDInterval(ctx context.Context, newForkID state
 		var forkIDs []state.ForkIDInterval
 		forkIDs = oldForkIDs
 		// Check to detect forkID inconsistencies
-		if forkIDs[len(forkIDs)-1].ForkId+1 != newForkID.ForkId {
-			log.Errorf("error checking forkID sequence. Last ForkID stored: %d. New ForkID received: %d", forkIDs[len(forkIDs)-1].ForkId, newForkID.ForkId)
-			return fmt.Errorf("error checking forkID sequence. Last ForkID stored: %d. New ForkID received: %d", forkIDs[len(forkIDs)-1].ForkId, newForkID.ForkId)
+		if forkIDs[len(forkIDs)-1].ForkId >= newForkID.ForkId {
+			errMsg := "error checking forkID sequence. Last ForkID stored: %d. New ForkID received: %d"
+			err := fmt.Errorf(errMsg, forkIDs[len(forkIDs)-1].ForkId, newForkID.ForkId)
+			log.Errorf(err.Error())
+			return err
 		}
 		forkIDs[len(forkIDs)-1].ToBatchNumber = newForkID.FromBatchNumber - 1
 		err := p.UpdateForkID(ctx, forkIDs[len(forkIDs)-1], dbTx)

state/pgstatestorage/forkid_external_test.go

@@ -0,0 +1,72 @@
+package pgstatestorage_test
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/0xPolygonHermez/zkevm-node/state"
+	"github.com/0xPolygonHermez/zkevm-node/state/pgstatestorage"
+	"github.com/0xPolygonHermez/zkevm-node/test/dbutils"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAddForkIDInterval(t *testing.T) {
+	if err := dbutils.InitOrResetState(stateDBCfg); err != nil {
+		panic(err)
+	}
+	pgStateStorage = pgstatestorage.NewPostgresStorage(state.Config{}, stateDb)
+	testState = state.NewState(stateCfg, pgstatestorage.NewPostgresStorage(stateCfg, stateDb), executorClient, stateTree, nil, nil)
+
+	for i := 1; i <= 6; i++ {
+		err = testState.AddForkID(ctx, state.ForkIDInterval{FromBatchNumber: uint64(i * 10), ToBatchNumber: uint64(i*10) + 9, ForkId: uint64(i)}, nil)
+		require.NoError(t, err)
+	}
+
+	testCases := []struct {
+		name          string
+		forkIDToAdd   state.ForkIDInterval
+		expectedError error
+	}{
+		{
+			name:          "fails to add because forkID already exists",
+			forkIDToAdd:   state.ForkIDInterval{ForkId: 3},
+			expectedError: fmt.Errorf("error checking forkID sequence. Last ForkID stored: 6. New ForkID received: 3"),
+		},
+		{
+			name:          "fails to add because forkID is smaller than the latest forkID",
+			forkIDToAdd:   state.ForkIDInterval{ForkId: 5},
+			expectedError: fmt.Errorf("error checking forkID sequence. Last ForkID stored: 6. New ForkID received: 5"),
+		},
+		{
+			name:          "fails to add because forkID is equal to the latest forkID",
+			forkIDToAdd:   state.ForkIDInterval{ForkId: 6},
+			expectedError: fmt.Errorf("error checking forkID sequence. Last ForkID stored: 6. New ForkID received: 6"),
+		},
+		{
+			name:          "adds successfully",
+			forkIDToAdd:   state.ForkIDInterval{ForkId: 7},
+			expectedError: nil,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := context.Background()
+			dbTx, err := testState.BeginStateTransaction(ctx)
+			require.NoError(t, err)
+
+			err = testState.AddForkIDInterval(ctx, tc.forkIDToAdd, dbTx)
+
+			if tc.expectedError == nil {
+				assert.Nil(t, err)
+			} else {
+				assert.Equal(t, tc.expectedError.Error(), err.Error())
+			}
+
+			require.NoError(t, dbTx.Commit(ctx))
+		})
+	}
+}