sql: use checksums to determine if indexes are outdated

Signed-off-by: Miguel Molina <miguel@erizocosmi.co>

sql/index.go

@@ -5,12 +5,21 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/sirupsen/logrus"
 	"gopkg.in/src-d/go-errors.v1"
 )
 
 // IndexBatchSize is the number of rows to save at a time when creating indexes.
 const IndexBatchSize = uint64(10000)
 
+// ChecksumKey is the key in an index config to store the checksum.
+const ChecksumKey = "checksum"
+
+// Checksumable tables can return a checksum of their data.
+type Checksumable interface {
+	Checksum() (string, error)
+}
+
 // PartitionIndexKeyValueIter is an iterator of partitions that will return
 // the partition and the IndexKeyValueIter of that partition.
 type PartitionIndexKeyValueIter interface {
@@ -211,17 +220,43 @@ func (r *IndexRegistry) LoadIndexes(dbs Databases) error {
 
 	for _, driver := range r.drivers {
 		for _, db := range dbs {
-			for t := range db.Tables() {
-				indexes, err := driver.LoadAll(db.Name(), t)
+			for _, t := range db.Tables() {
+				indexes, err := driver.LoadAll(db.Name(), t.Name())
 				if err != nil {
 					return err
 				}
 
+				var checksum string
+				if c, ok := t.(Checksumable); ok {
+					checksum, err = c.Checksum()
+					if err != nil {
+						return err
+					}
+				}
+
 				for _, idx := range indexes {
 					k := indexKey{db.Name(), idx.ID()}
 					r.indexes[k] = idx
 					r.indexOrder = append(r.indexOrder, k)
-					r.statuses[k] = IndexReady
+
+					var idxChecksum string
+					if c, ok := idx.(Checksumable); ok {
+						idxChecksum, err = c.Checksum()
+						if err != nil {
+							return err
+						}
+					}
+
+					if checksum == "" || checksum == idxChecksum {
+						r.statuses[k] = IndexReady
+					} else {
+						logrus.Warnf(
+							"index %q is outdated and will not be used, you can remove it using `DROP INDEX %s`",
+							idx.ID(),
+							idx.ID(),
+						)
+						r.statuses[k] = IndexOutdated
+					}
 				}
 			}
 		}
@@ -244,6 +279,18 @@ func (r *IndexRegistry) CanUseIndex(idx Index) bool {
 	return r.canUseIndex(idx)
 }
 
+// CanRemoveIndex returns whether the given index is ready to be removed.
+func (r *IndexRegistry) CanRemoveIndex(idx Index) bool {
+	if idx == nil {
+		return false
+	}
+
+	r.mut.RLock()
+	defer r.mut.RUnlock()
+	status := r.statuses[indexKey{idx.Database(), idx.ID()}]
+	return status == IndexReady || status == IndexOutdated
+}
+
 func (r *IndexRegistry) canUseIndex(idx Index) bool {
 	if idx == nil {
 		return false
@@ -400,8 +447,8 @@ var (
 	ErrIndexNotFound = errors.NewKind("index %q	was not found")
 
 	// ErrIndexDeleteInvalidStatus is returned when the index trying to delete
-	// does not have a ready state.
-	ErrIndexDeleteInvalidStatus = errors.NewKind("can't delete index %q because it's not ready for usage")
+	// does not have a ready or outdated state.
+	ErrIndexDeleteInvalidStatus = errors.NewKind("can't delete index %q because it's not ready for removal")
 )
 
 func (r *IndexRegistry) validateIndexToAdd(idx Index) error {
@@ -507,7 +554,7 @@ func (r *IndexRegistry) DeleteIndex(db, id string, force bool) (<-chan struct{},
 	var key indexKey
 	for k, idx := range r.indexes {
 		if strings.ToLower(id) == idx.ID() {
-			if !force && !r.CanUseIndex(idx) {
+			if !force && !r.CanRemoveIndex(idx) {
 				r.mut.RUnlock()
 				return nil, ErrIndexDeleteInvalidStatus.New(id)
 			}
@@ -563,13 +610,16 @@ func (r *IndexRegistry) DeleteIndex(db, id string, force bool) (<-chan struct{},
 }
 
 // IndexStatus represents the current status in which the index is.
-type IndexStatus bool
+type IndexStatus byte
 
 const (
 	// IndexNotReady means the index is not ready to be used.
-	IndexNotReady IndexStatus = false
+	IndexNotReady IndexStatus = iota
 	// IndexReady means the index can be used.
-	IndexReady IndexStatus = true
+	IndexReady
+	// IndexOutdated means the index is loaded but will not be used because the
+	// contents in it are outdated.
+	IndexOutdated
 )
 
 // IsUsable returns whether the index can be used or not based on the status.

sql/index/pilosa/index.go

@@ -67,19 +67,33 @@ type pilosaIndex struct {
 	table       string
 	id          string
 	expressions []string
+	checksum    string
 }
 
 func newPilosaIndex(idx *pilosa.Index, mapping *mapping, cfg *index.Config) *pilosaIndex {
+	var checksum string
+	for _, c := range cfg.Drivers {
+		if ch, ok := c[sql.ChecksumKey]; ok {
+			checksum = ch
+		}
+		break
+	}
+
 	return &pilosaIndex{
 		index:       newConcurrentPilosaIndex(idx),
 		db:          cfg.DB,
 		table:       cfg.Table,
 		id:          cfg.ID,
 		expressions: cfg.Expressions,
 		mapping:     mapping,
+		checksum:    checksum,
 	}
 }
 
+func (idx *pilosaIndex) Checksum() (string, error) {
+	return idx.checksum, nil
+}
+
 // Get returns an IndexLookup for the given key in the index.
 // If key parameter is not present then the returned iterator
 // will go through all the locations on the index.

sql/index_test.go

@@ -299,6 +299,40 @@ func TestLoadIndexes(t *testing.T) {
 	}
 }
 
+func TestLoadOutdatedIndexes(t *testing.T) {
+	require := require.New(t)
+
+	d := &loadDriver{id: "d1", indexes: []Index{
+		&checksumIndex{&dummyIdx{id: "idx1", database: "db1", table: "t1"}, "2"},
+		&checksumIndex{&dummyIdx{id: "idx2", database: "db1", table: "t2"}, "2"},
+	}}
+
+	registry := NewIndexRegistry()
+	registry.RegisterIndexDriver(d)
+
+	dbs := Databases{
+		dummyDB{
+			name: "db1",
+			tables: map[string]Table{
+				"t1": &checksumTable{&dummyTable{name: "t1"}, "2"},
+				"t2": &checksumTable{&dummyTable{name: "t2"}, "1"},
+			},
+		},
+	}
+
+	require.NoError(registry.LoadIndexes(dbs))
+
+	var result []Index
+	for _, idx := range registry.indexes {
+		result = append(result, idx)
+	}
+
+	require.ElementsMatch(d.indexes, result)
+
+	require.Equal(registry.statuses[indexKey{"db1", "idx1"}], IndexReady)
+	require.Equal(registry.statuses[indexKey{"db1", "idx2"}], IndexOutdated)
+}
+
 type dummyDB struct {
 	name   string
 	tables map[string]Table
@@ -377,3 +411,21 @@ func (dummyExpr) Type() Type       { panic("not implemented") }
 func (e dummyExpr) WithIndex(idx int) Expression {
 	return &dummyExpr{idx, e.colName}
 }
+
+type checksumTable struct {
+	Table
+	checksum string
+}
+
+func (t *checksumTable) Checksum() (string, error) {
+	return t.checksum, nil
+}
+
+type checksumIndex struct {
+	Index
+	checksum string
+}
+
+func (idx *checksumIndex) Checksum() (string, error) {
+	return idx.checksum, nil
+}

sql/plan/create_index.go

@@ -81,7 +81,7 @@ func getIndexableTable(t sql.Table) (sql.IndexableTable, error) {
 	case sql.TableWrapper:
 		return getIndexableTable(t.Underlying())
 	default:
-		return nil, ErrInsertIntoNotSupported.New()
+		return nil, ErrNotIndexable.New()
 	}
 }
 
@@ -119,6 +119,13 @@ func (c *CreateIndex) RowIter(ctx *sql.Context) (sql.RowIter, error) {
 		}
 	}
 
+	if ch, ok := table.Table.(sql.Checksumable); ok {
+		c.Config[sql.ChecksumKey], err = ch.Checksum()
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	index, err := driver.Create(
 		c.CurrentDatabase,
 		table.Name(),

sql/plan/create_index_test.go

@@ -171,6 +171,44 @@ func TestCreateIndexSync(t *testing.T) {
 	require.True(found)
 }
 
+func TestCreateIndexChecksum(t *testing.T) {
+	require := require.New(t)
+
+	table := &checksumTable{
+		mem.NewTable("foo", sql.Schema{
+			{Name: "a", Source: "foo"},
+			{Name: "b", Source: "foo"},
+			{Name: "c", Source: "foo"},
+		}),
+		"1",
+	}
+
+	driver := new(mockDriver)
+	catalog := sql.NewCatalog()
+	catalog.RegisterIndexDriver(driver)
+	db := mem.NewDatabase("foo")
+	db.AddTable("foo", table)
+	catalog.AddDatabase(db)
+
+	exprs := []sql.Expression{
+		expression.NewGetFieldWithTable(2, sql.Int64, "foo", "c", true),
+		expression.NewGetFieldWithTable(0, sql.Int64, "foo", "a", true),
+	}
+
+	ci := NewCreateIndex(
+		"idx", NewResolvedTable(table), exprs, "mock",
+		map[string]string{"async": "false"},
+	)
+	ci.Catalog = catalog
+	ci.CurrentDatabase = "foo"
+
+	_, err := ci.RowIter(sql.NewEmptyContext())
+	require.NoError(err)
+
+	require.Equal([]string{"idx"}, driver.saved)
+	require.Equal("1", driver.config["idx"][sql.ChecksumKey])
+}
+
 func TestCreateIndexWithIter(t *testing.T) {
 	require := require.New(t)
 	foo := mem.NewPartitionedTable("foo", sql.Schema{
@@ -283,14 +321,20 @@ func (i *mockIndex) Has(sql.Partition, ...interface{}) (bool, error) {
 func (*mockIndex) Driver() string { return "mock" }
 
 type mockDriver struct {
+	config  map[string]map[string]string
 	deleted []string
 	saved   []string
 }
 
 var _ sql.IndexDriver = (*mockDriver)(nil)
 
 func (*mockDriver) ID() string { return "mock" }
-func (*mockDriver) Create(db, table, id string, exprs []sql.Expression, config map[string]string) (sql.Index, error) {
+func (d *mockDriver) Create(db, table, id string, exprs []sql.Expression, config map[string]string) (sql.Index, error) {
+	if d.config == nil {
+		d.config = make(map[string]map[string]string)
+	}
+	d.config[id] = config
+
 	return &mockIndex{db, table, id, exprs}, nil
 }
 func (*mockDriver) LoadAll(db, table string) ([]sql.Index, error) {
@@ -305,3 +349,14 @@ func (d *mockDriver) Delete(index sql.Index, _ sql.PartitionIter) error {
 	d.deleted = append(d.deleted, index.ID())
 	return nil
 }
+
+type checksumTable struct {
+	sql.Table
+	checksum string
+}
+
+func (t *checksumTable) Checksum() (string, error) {
+	return t.checksum, nil
+}
+
+func (t *checksumTable) Underlying() sql.Table { return t.Table }