Handle unknown migrations in ToApply()

Author: ericklaus-wf

migrate.go

@@ -364,9 +364,11 @@ func PlanMigration(db *sql.DB, dialect string, m MigrationSource, dir MigrationD
 	if len(existingMigrations) > 0 {
 		result = append(result, ToCatchup(migrations, existingMigrations, record)...)
 	}
-
 	// Figure out which migrations to apply
-	toApply := ToApply(migrations, record.Id, dir)
+	toApply := ToApply(migrations, existingMigrations, dir)
+	if err != nil {
+		return nil, nil, err
+	}
 	toApplyCount := len(toApply)
 	if max > 0 && max < toApplyCount {
 		toApplyCount = max
@@ -379,6 +381,10 @@ func PlanMigration(db *sql.DB, dialect string, m MigrationSource, dir MigrationD
 				Queries:   v.Up,
 			})
 		} else if dir == Down {
+			if v.Down == nil {
+				// This happens if we are trying to migrate down a migration unknown to us
+				return nil, nil, fmt.Errorf("Unable to undo unknown migration %q", v.Id)
+			}
 			result = append(result, &PlannedMigration{
 				Migration: v,
 				Queries:   v.Down,
@@ -389,34 +395,74 @@ func PlanMigration(db *sql.DB, dialect string, m MigrationSource, dir MigrationD
 	return result, dbMap, nil
 }
 
-// Filter a slice of migrations into ones that should be applied.
-func ToApply(migrations []*Migration, current string, direction MigrationDirection) []*Migration {
-	var index = -1
-	if current != "" {
-		for index < len(migrations)-1 {
-			index++
-			if migrations[index].Id == current {
+// Searches the arrays for the latest elements with common ids.
+// Returns the indexes of the common id.
+func lastCommon(left []*Migration, right []*Migration) (int, int) {
+	xIndexMatch := -1
+	yIndexMatch := 0
+	for i := 0; i < len(left); i++ {
+		existingId := left[i].Id
+		for j := yIndexMatch; j < len(right); j++ {
+			if right[j].Id == existingId {
+				xIndexMatch = i
+				yIndexMatch = j
 				break
 			}
 		}
 	}
+	if xIndexMatch == -1 {
+		return -1, -1 // We never found a match; the arrays have nothing in common
+	}
+	return xIndexMatch, yIndexMatch
+}
 
+// Filter a slice of migrations into ones that should be applied.
+func ToApply(migrations, existingMigrations []*Migration, direction MigrationDirection) []*Migration {
 	if direction == Up {
-		return migrations[index+1:]
-	} else if direction == Down {
-		if index == -1 {
-			return []*Migration{}
-		}
+		return toApplyUp(migrations, existingMigrations)
+	}
+	if direction == Down {
+		return toApplyDown(migrations, existingMigrations)
+	}
+	panic("Unknown direction")
+}
 
-		// Add in reverse order
-		toApply := make([]*Migration, index+1)
-		for i := 0; i < index+1; i++ {
-			toApply[index-i] = migrations[i]
-		}
-		return toApply
+func toApplyUp(migrations, existingMigrations []*Migration) []*Migration {
+	if len(existingMigrations) == 0 {
+		return migrations
+	}
+	_, index := lastCommon(existingMigrations, migrations)
+	return migrations[index+1:]
+}
+
+func toApplyDown(migrations, existingMigrations []*Migration) []*Migration {
+	if len(existingMigrations) == -1 {
+		return []*Migration{}
+	}
+	// When a Migration appears in both existingMigrations and migrations,
+	// we want the Migration from migrations, since only that list has
+	// the Up and Down fields set.
+	migrationsMap := map[string]*Migration{}
+	for _, m := range existingMigrations {
+		// existingMigrations will not have Up or Down set
+		migrationsMap[m.Id] = m
+	}
+	for _, m := range migrations {
+		migrationsMap[m.Id] = m
 	}
+	allMigrations := make([]*Migration, 0, len(migrationsMap))
+	for _, m := range migrationsMap {
+		allMigrations = append(allMigrations, m)
+	}
+	sort.Sort(byId(allMigrations))
 
-	panic("Not possible")
+	_, index := lastCommon(existingMigrations, allMigrations)
+	// Add in reverse order
+	toApply := make([]*Migration, index+1)
+	for i := 0; i < index+1; i++ {
+		toApply[index-i] = allMigrations[i]
+	}
+	return toApply
 }
 
 func ToCatchup(migrations, existingMigrations []*Migration, lastRun *Migration) []*PlannedMigration {

migrate_test.go

@@ -360,6 +360,97 @@ func (s *SqliteMigrateSuite) TestPlanMigrationWithHoles(c *C) {
 	c.Assert(plannedMigrations[2].Queries[0], Equals, down)
 }
 
+func (s *SqliteMigrateSuite) TestMigrationWithMostRecentUnknown(c *C) {
+	up := "SELECT 0"
+	down := "SELECT 1"
+	migrations := &MemoryMigrationSource{
+		Migrations: []*Migration{
+			&Migration{
+				Id:   "1",
+				Up:   []string{up},
+				Down: []string{down},
+			},
+			&Migration{
+				Id:   "3",
+				Up:   []string{up},
+				Down: []string{down},
+			},
+			&Migration{
+				Id:   "4",
+				Up:   []string{up},
+				Down: []string{down},
+			},
+		},
+	}
+	n, err := Exec(s.Db, "sqlite3", migrations, Up)
+	c.Assert(err, IsNil)
+	c.Assert(n, Equals, 3)
+
+	// remove "4" from our list of known migrations
+	migrations.Migrations = migrations.Migrations[0:2]
+
+	migrations.Migrations = append(migrations.Migrations, &Migration{
+		Id:   "2",
+		Up:   []string{up},
+		Down: []string{down},
+	}, &Migration{
+		Id:   "5",
+		Up:   []string{up},
+		Down: []string{down},
+	})
+
+	// apply the latest migration
+	plannedMigrations, _, err := PlanMigration(s.Db, "sqlite3", migrations, Up, 0)
+	c.Assert(err, IsNil)
+	c.Assert(plannedMigrations, HasLen, 2)
+	c.Assert(plannedMigrations[0].Migration.Id, Equals, "2")
+	c.Assert(plannedMigrations[1].Migration.Id, Equals, "5")
+
+	// The most recent migration is unknown; we can't undo it
+	plannedMigrations, _, err = PlanMigration(s.Db, "sqlite3", migrations, Down, 1)
+	c.Assert(err, Not(IsNil))
+}
+
+func (s *SqliteMigrateSuite) TestMigrationDownWithMiddleUnknown(c *C) {
+	up := "SELECT 0"
+	down := "SELECT 1"
+	migrations := &MemoryMigrationSource{
+		Migrations: []*Migration{
+			&Migration{
+				Id:   "1",
+				Up:   []string{up},
+				Down: []string{down},
+			},
+			&Migration{
+				Id:   "2",
+				Up:   []string{up},
+				Down: []string{down},
+			},
+			&Migration{
+				Id:   "3",
+				Up:   []string{up},
+				Down: []string{down},
+			},
+		},
+	}
+	n, err := Exec(s.Db, "sqlite3", migrations, Up)
+	c.Assert(err, IsNil)
+	c.Assert(n, Equals, 3)
+
+	// remove "2" from our list of known migrations
+	migrations.Migrations = []*Migration{migrations.Migrations[0], migrations.Migrations[2]}
+
+	// undo "3"
+	plannedMigrations, _, err := PlanMigration(s.Db, "sqlite3", migrations, Down, 1)
+	c.Assert(err, IsNil)
+	c.Assert(plannedMigrations, HasLen, 1)
+	c.Assert(plannedMigrations[0].Id, Equals, "3")
+
+	// will undo "3", then try "2", but "2" is unknown
+	plannedMigrations, _, err = PlanMigration(s.Db, "sqlite3", migrations, Down, 2)
+	c.Assert(err, Not(IsNil))
+}
+
 func (s *SqliteMigrateSuite) TestLess(c *C) {
 	c.Assert((Migration{Id: "1"}).Less(&Migration{Id: "2"}), Equals, true)           // 1 less than 2
 	c.Assert((Migration{Id: "2"}).Less(&Migration{Id: "1"}), Equals, false)          // 2 not less than 1

toapply_test.go

@@ -17,60 +17,51 @@ type ToApplyMigrateSuite struct {
 var _ = Suite(&ToApplyMigrateSuite{})
 
 func (s *ToApplyMigrateSuite) TestGetAll(c *C) {
-	toApply := ToApply(toapplyMigrations, "", Up)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:0], Up)
 	c.Assert(toApply, HasLen, 3)
 	c.Assert(toApply[0], Equals, toapplyMigrations[0])
 	c.Assert(toApply[1], Equals, toapplyMigrations[1])
 	c.Assert(toApply[2], Equals, toapplyMigrations[2])
 }
 
 func (s *ToApplyMigrateSuite) TestGetAbc(c *C) {
-	toApply := ToApply(toapplyMigrations, "abc", Up)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:1], Up)
 	c.Assert(toApply, HasLen, 2)
 	c.Assert(toApply[0], Equals, toapplyMigrations[1])
 	c.Assert(toApply[1], Equals, toapplyMigrations[2])
 }
 
 func (s *ToApplyMigrateSuite) TestGetCde(c *C) {
-	toApply := ToApply(toapplyMigrations, "cde", Up)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:2], Up)
 	c.Assert(toApply, HasLen, 1)
 	c.Assert(toApply[0], Equals, toapplyMigrations[2])
 }
 
 func (s *ToApplyMigrateSuite) TestGetDone(c *C) {
-	toApply := ToApply(toapplyMigrations, "efg", Up)
-	c.Assert(toApply, HasLen, 0)
-
-	toApply = ToApply(toapplyMigrations, "zzz", Up)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:3], Up)
 	c.Assert(toApply, HasLen, 0)
 }
 
 func (s *ToApplyMigrateSuite) TestDownDone(c *C) {
-	toApply := ToApply(toapplyMigrations, "", Down)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:0], Down)
 	c.Assert(toApply, HasLen, 0)
 }
 
 func (s *ToApplyMigrateSuite) TestDownCde(c *C) {
-	toApply := ToApply(toapplyMigrations, "cde", Down)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:2], Down)
 	c.Assert(toApply, HasLen, 2)
 	c.Assert(toApply[0], Equals, toapplyMigrations[1])
 	c.Assert(toApply[1], Equals, toapplyMigrations[0])
 }
 
 func (s *ToApplyMigrateSuite) TestDownAbc(c *C) {
-	toApply := ToApply(toapplyMigrations, "abc", Down)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations[0:1], Down)
 	c.Assert(toApply, HasLen, 1)
 	c.Assert(toApply[0], Equals, toapplyMigrations[0])
 }
 
 func (s *ToApplyMigrateSuite) TestDownAll(c *C) {
-	toApply := ToApply(toapplyMigrations, "efg", Down)
-	c.Assert(toApply, HasLen, 3)
-	c.Assert(toApply[0], Equals, toapplyMigrations[2])
-	c.Assert(toApply[1], Equals, toapplyMigrations[1])
-	c.Assert(toApply[2], Equals, toapplyMigrations[0])
-
-	toApply = ToApply(toapplyMigrations, "zzz", Down)
+	toApply := ToApply(toapplyMigrations, toapplyMigrations, Down)
 	c.Assert(toApply, HasLen, 3)
 	c.Assert(toApply[0], Equals, toapplyMigrations[2])
 	c.Assert(toApply[1], Equals, toapplyMigrations[1])
@@ -88,13 +79,13 @@ func (s *ToApplyMigrateSuite) TestAlphaNumericMigrations(c *C) {
 
 	sort.Sort(migrations)
 
-	toApplyUp := ToApply(migrations, "2_cde", Up)
+	toApplyUp := ToApply(migrations, migrations[0:2], Up)
 	c.Assert(toApplyUp, HasLen, 3)
 	c.Assert(toApplyUp[0].Id, Equals, "10_abc")
 	c.Assert(toApplyUp[1].Id, Equals, "35_cde")
 	c.Assert(toApplyUp[2].Id, Equals, "efg")
 
-	toApplyDown := ToApply(migrations, "2_cde", Down)
+	toApplyDown := ToApply(migrations, migrations[0:2], Down)
 	c.Assert(toApplyDown, HasLen, 2)
 	c.Assert(toApplyDown[0].Id, Equals, "2_cde")
 	c.Assert(toApplyDown[1].Id, Equals, "1_abc")