internal storage engine: improve compile-time typing
This change does to internal storage engine API changes.
First, renaming Snapshot.Close() -> Snapshot.Abort().
Before this change, the Store interface implemented the
Snapshot interface, now it doesn't.
Second, adding the SnapshotOrTranscation interface.
Only Snapshot and Transaction implement this interface.
Transaction doesn't implement Snapshot.
Third, the StoreReadWriter becomes private. The StoreReadWriter
was replaced by the Transaction. This was done because in lots
of places the StoreReadWriter was checked to be the Transaction
at runtime.
This change also updates the code to the new API and removes
extra runtime type checking.
MultiPart: 1/2
Change-Id: Ic213cc0479a6cd8604bc62c29edaf7adb95b260e
diff --git a/services/syncbase/server/watchable/transaction.go b/services/syncbase/server/watchable/transaction.go
index 93b6b33..fb82f72 100644
--- a/services/syncbase/server/watchable/transaction.go
+++ b/services/syncbase/server/watchable/transaction.go
@@ -177,7 +177,7 @@
// operations (create, join, leave, destroy) to notify the sync watcher of the
// change at its proper position in the timeline (the transaction commit).
// Note: this is an internal function used by sync, not part of the interface.
-func AddSyncGroupOp(ctx *context.T, tx store.StoreReadWriter, prefixes []string, remove bool) error {
+func AddSyncGroupOp(ctx *context.T, tx store.Transaction, prefixes []string, remove bool) error {
wtx := tx.(*transaction)
wtx.mu.Lock()
defer wtx.mu.Unlock()
@@ -195,7 +195,7 @@
// current keys and their versions to use when initializing the sync metadata
// at the point in the timeline when these keys become syncable (at commit).
// Note: this is an internal function used by sync, not part of the interface.
-func AddSyncSnapshotOp(ctx *context.T, tx store.StoreReadWriter, key, version []byte) error {
+func AddSyncSnapshotOp(ctx *context.T, tx store.Transaction, key, version []byte) error {
wtx := tx.(*transaction)
wtx.mu.Lock()
defer wtx.mu.Unlock()
@@ -227,10 +227,10 @@
// GetVersion returns the current version of a managed key. This method is used
// by the Sync module when the initiator is attempting to add new versions of
// objects. Reading the version key is used for optimistic concurrency
-// control. At minimum, an object implementing the StoreReader interface is
+// control. At minimum, an object implementing the Transaction interface is
// required since this is a Get operation.
-func GetVersion(ctx *context.T, st store.StoreReader, key []byte) ([]byte, error) {
- switch w := st.(type) {
+func GetVersion(ctx *context.T, tx store.Transaction, key []byte) ([]byte, error) {
+ switch w := tx.(type) {
case *transaction:
w.mu.Lock()
defer w.mu.Unlock()
@@ -238,8 +238,6 @@
return nil, convertError(w.err)
}
return getVersion(w.itx, key)
- case *wstore:
- return getVersion(w.ist, key)
}
return nil, verror.New(verror.ErrInternal, ctx, "unsupported store type")
}
@@ -266,8 +264,8 @@
// PutAtVersion puts a value for the managed key at the requested version. This
// method is used by the Sync module exclusively when the initiator adds objects
// with versions created on other Syncbases. At minimum, an object implementing
-// the StoreReadWriter interface is required since this is a Put operation.
-func PutAtVersion(ctx *context.T, tx store.StoreReadWriter, key, valbuf, version []byte) error {
+// the Transaction interface is required since this is a Put operation.
+func PutAtVersion(ctx *context.T, tx store.Transaction, key, valbuf, version []byte) error {
wtx := tx.(*transaction)
wtx.mu.Lock()
@@ -285,8 +283,8 @@
// version. This method is used by the Sync module exclusively when the
// initiator selects which of the already stored versions (via PutAtVersion
// calls) becomes the current version. At minimum, an object implementing
-// the StoreReadWriter interface is required since this is a Put operation.
-func PutVersion(ctx *context.T, tx store.StoreReadWriter, key, version []byte) error {
+// the Transaction interface is required since this is a Put operation.
+func PutVersion(ctx *context.T, tx store.Transaction, key, version []byte) error {
wtx := tx.(*transaction)
wtx.mu.Lock()
