gitaly: Add `deleteKey` operation to `TransactionManager`

When we apply an operation from the write-ahead log, we also want to
remove that entry from the log. Before we add this logic, it is
necessary that `TransactionManager` supports deletion.

This commit modifies the `databaseTransaction` interface to add a
`Delete` function and also adds a `deleteKey` function to the
`TransactionManager`.

2 files changed, 19 insertions, 1 deletions

diff --git a/internal/gitaly/database.go b/internal/gitaly/database.go
index 2015de710..b2b1bb040 100644
--- a/internal/gitaly/database.go
+++ b/internal/gitaly/database.go
@@ -31,16 +31,22 @@ func (db databaseAdapter) NewWriteBatch() writeBatch {
 	return db.DB.NewWriteBatch()
 }
 
-// NewWriteBatch calls badger.*DB.View. Refer to Badger's documentation for details.
+// View calls badger.*DB.View. Refer to Badger's documentation for details.
 func (db databaseAdapter) View(handler func(databaseTransaction) error) error {
 	return db.DB.View(func(txn *badger.Txn) error { return handler(txn) })
 }
 
+// Update calls badger.*DB.View. Refer to Badger's documentation for details.
+func (db databaseAdapter) Update(handler func(databaseTransaction) error) error {
+	return db.DB.Update(func(txn *badger.Txn) error { return handler(txn) })
+}
+
 // database is the Badger.DB interface used by TransactionManager. Refer to Badger's documentation
 // for details.
 type database interface {
 	NewWriteBatch() writeBatch
 	View(func(databaseTransaction) error) error
+	Update(func(databaseTransaction) error) error
 }
 
 // writeBatch is the interface of Badger.WriteBatch used by TransactionManager. Refer to Badger's
@@ -55,5 +61,6 @@ type writeBatch interface {
 // documentation for details
 type databaseTransaction interface {
 	Get([]byte) (*badger.Item, error)
+	Delete([]byte) error
 	NewIterator(badger.IteratorOptions) *badger.Iterator
 }
diff --git a/internal/gitaly/transaction_manager.go b/internal/gitaly/transaction_manager.go
index c9c89bf81..7603dc3aa 100644
--- a/internal/gitaly/transaction_manager.go
+++ b/internal/gitaly/transaction_manager.go
@@ -514,6 +514,17 @@ func (mgr *TransactionManager) readKey(key []byte, destination proto.Message) er
 	})
 }
 
+// deleteKey deletes a key from the database.
+func (mgr *TransactionManager) deleteKey(key []byte) error {
+	return mgr.db.Update(func(txn databaseTransaction) error {
+		if err := txn.Delete(key); err != nil {
+			return fmt.Errorf("delete: %w", err)
+		}
+
+		return nil
+	})
+}
+
 // getRepositoryID returns a repository's ID. The ID should never change as it is used in the database
 // keys. Gitaly does not have a permanent ID to use yet so the repository's storage name and relative
 // path are used as a composite key.