lmdb/badger: change (fix?) and simplify queries (offsets and created_at stuff should be simpler and q-dependent).

badger/migrations.go

@@ -0,0 +1,68 @@
+package badger
+
+import (
+	"encoding/binary"
+	"log"
+
+	"github.com/dgraph-io/badger/v4"
+)
+
+func (b *BadgerBackend) runMigrations() error {
+	return b.View(func(txn *badger.Txn) error {
+		item, err := txn.Get([]byte{dbVersionKey})
+		if err != nil {
+			return err
+		}
+		item.Value(func(val []byte) error {
+			var version uint16
+
+			// do the migrations in increasing steps (there is no rollback)
+			//
+
+			if version < 1 {
+				log.Println("migration 1: move all keys from indexTag to indexTag32 if they are 32-bytes")
+				prefix := []byte{indexTagPrefix}
+				it := txn.NewIterator(badger.IteratorOptions{
+					PrefetchValues: true,
+					PrefetchSize:   100,
+					Prefix:         prefix,
+				})
+				defer it.Close()
+
+				for it.Seek(prefix); it.ValidForPrefix(prefix); it.Next() {
+					item := it.Item()
+					key := item.Key()
+
+					if len(key) == 1+32+2+4 {
+						// it's 32 bytes
+						log.Printf("moving key %x", key)
+						if err := txn.Delete(key); err != nil {
+							return err
+						}
+						key[0] = indexTag32Prefix
+						txn.Set(key, nil)
+					}
+				}
+
+				// bump version
+				if err := b.bumpVersion(txn, 1); err != nil {
+					return err
+				}
+			}
+
+			if version < 2 {
+				// ...
+			}
+
+			return nil
+		})
+
+		return nil
+	})
+}
+
+func (b *BadgerBackend) bumpVersion(txn *badger.Txn, version uint16) error {
+	buf := make([]byte, 2)
+	binary.BigEndian.PutUint16(buf, version)
+	return txn.Set([]byte{dbVersionKey}, buf)
+}