chore: switch database engine to sqlite (fixes #9954) (#9965)

Switch the database from LevelDB to SQLite, for greater stability and
simpler code.

Co-authored-by: Tommy van der Vorst <tommy@pixelspark.nl>
Co-authored-by: bt90 <btom1990@googlemail.com>

internal/db/olddb/transactions.go

@@ -0,0 +1,193 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package olddb
+
+import (
+	"fmt"
+
+	"google.golang.org/protobuf/proto"
+
+	"github.com/syncthing/syncthing/internal/db/olddb/backend"
+	"github.com/syncthing/syncthing/internal/gen/bep"
+	"github.com/syncthing/syncthing/internal/gen/dbproto"
+	"github.com/syncthing/syncthing/lib/protocol"
+)
+
+// A readOnlyTransaction represents a database snapshot.
+type readOnlyTransaction struct {
+	backend.ReadTransaction
+	keyer keyer
+}
+
+func (db *deprecatedLowlevel) newReadOnlyTransaction() (readOnlyTransaction, error) {
+	tran, err := db.NewReadTransaction()
+	if err != nil {
+		return readOnlyTransaction{}, err
+	}
+	return db.readOnlyTransactionFromBackendTransaction(tran), nil
+}
+
+func (db *deprecatedLowlevel) readOnlyTransactionFromBackendTransaction(tran backend.ReadTransaction) readOnlyTransaction {
+	return readOnlyTransaction{
+		ReadTransaction: tran,
+		keyer:           db.keyer,
+	}
+}
+
+func (t readOnlyTransaction) close() {
+	t.Release()
+}
+
+func (t readOnlyTransaction) getFileByKey(key []byte) (protocol.FileInfo, bool, error) {
+	f, ok, err := t.getFileTrunc(key, false)
+	if err != nil || !ok {
+		return protocol.FileInfo{}, false, err
+	}
+	return f, true, nil
+}
+
+func (t readOnlyTransaction) getFileTrunc(key []byte, trunc bool) (protocol.FileInfo, bool, error) {
+	bs, err := t.Get(key)
+	if backend.IsNotFound(err) {
+		return protocol.FileInfo{}, false, nil
+	}
+	if err != nil {
+		return protocol.FileInfo{}, false, err
+	}
+	f, err := t.unmarshalTrunc(bs, trunc)
+	if backend.IsNotFound(err) {
+		return protocol.FileInfo{}, false, nil
+	}
+	if err != nil {
+		return protocol.FileInfo{}, false, err
+	}
+	return f, true, nil
+}
+
+func (t readOnlyTransaction) unmarshalTrunc(bs []byte, trunc bool) (protocol.FileInfo, error) {
+	if trunc {
+		var bfi dbproto.FileInfoTruncated
+		err := proto.Unmarshal(bs, &bfi)
+		if err != nil {
+			return protocol.FileInfo{}, err
+		}
+		if err := t.fillTruncated(&bfi); err != nil {
+			return protocol.FileInfo{}, err
+		}
+		return protocol.FileInfoFromDBTruncated(&bfi), nil
+	}
+
+	var bfi bep.FileInfo
+	err := proto.Unmarshal(bs, &bfi)
+	if err != nil {
+		return protocol.FileInfo{}, err
+	}
+	if err := t.fillFileInfo(&bfi); err != nil {
+		return protocol.FileInfo{}, err
+	}
+	return protocol.FileInfoFromDB(&bfi), nil
+}
+
+type blocksIndirectionError struct {
+	err error
+}
+
+func (e *blocksIndirectionError) Error() string {
+	return fmt.Sprintf("filling Blocks: %v", e.err)
+}
+
+func (e *blocksIndirectionError) Unwrap() error {
+	return e.err
+}
+
+// fillFileInfo follows the (possible) indirection of blocks and version
+// vector and fills it out.
+func (t readOnlyTransaction) fillFileInfo(fi *bep.FileInfo) error {
+	var key []byte
+
+	if len(fi.Blocks) == 0 && len(fi.BlocksHash) != 0 {
+		// The blocks list is indirected and we need to load it.
+		key = t.keyer.GenerateBlockListKey(key, fi.BlocksHash)
+		bs, err := t.Get(key)
+		if err != nil {
+			return &blocksIndirectionError{err}
+		}
+		var bl dbproto.BlockList
+		if err := proto.Unmarshal(bs, &bl); err != nil {
+			return err
+		}
+		fi.Blocks = bl.Blocks
+	}
+
+	if len(fi.VersionHash) != 0 {
+		key = t.keyer.GenerateVersionKey(key, fi.VersionHash)
+		bs, err := t.Get(key)
+		if err != nil {
+			return fmt.Errorf("filling Version: %w", err)
+		}
+		var v bep.Vector
+		if err := proto.Unmarshal(bs, &v); err != nil {
+			return err
+		}
+		fi.Version = &v
+	}
+
+	return nil
+}
+
+// fillTruncated follows the (possible) indirection of version vector and
+// fills it.
+func (t readOnlyTransaction) fillTruncated(fi *dbproto.FileInfoTruncated) error {
+	var key []byte
+
+	if len(fi.VersionHash) == 0 {
+		return nil
+	}
+
+	key = t.keyer.GenerateVersionKey(key, fi.VersionHash)
+	bs, err := t.Get(key)
+	if err != nil {
+		return err
+	}
+	var v bep.Vector
+	if err := proto.Unmarshal(bs, &v); err != nil {
+		return err
+	}
+	fi.Version = &v
+	return nil
+}
+
+func (t *readOnlyTransaction) withHaveSequence(folder []byte, startSeq int64, fn Iterator) error {
+	first, err := t.keyer.GenerateSequenceKey(nil, folder, startSeq)
+	if err != nil {
+		return err
+	}
+	last, err := t.keyer.GenerateSequenceKey(nil, folder, maxInt64)
+	if err != nil {
+		return err
+	}
+	dbi, err := t.NewRangeIterator(first, last)
+	if err != nil {
+		return err
+	}
+	defer dbi.Release()
+
+	for dbi.Next() {
+		f, ok, err := t.getFileByKey(dbi.Value())
+		if err != nil {
+			return err
+		}
+		if !ok {
+			continue
+		}
+
+		if !fn(f) {
+			return nil
+		}
+	}
+	return dbi.Error()
+}