store API: update comments
Resolve a TODO by update a comment for Put. The new comment reflects
the current state of things.
Change-Id: Ie458696f6d1c1c41749208d5e11ce92d6a6ef58e
diff --git a/services/syncbase/store/model.go b/services/syncbase/store/model.go
index be7265d..504ae01 100644
--- a/services/syncbase/store/model.go
+++ b/services/syncbase/store/model.go
@@ -6,9 +6,6 @@
// Currently, this API and its implementations are meant to be internal.
package store
-// TODO(sadovsky): Decide whether to defensively copy passed-in []byte's vs.
-// requiring clients not to modify passed-in []byte's.
-
// StoreReader reads data from a CRUD-capable storage engine.
type StoreReader interface {
// Get returns the value for the given key. The returned slice may be a
@@ -17,6 +14,8 @@
// nil valbuf.
// If the given key is unknown, valbuf is returned unchanged and the function
// fails with ErrUnknownKey.
+ //
+ // It is safe to modify the contents of the key after Get returns.
Get(key, valbuf []byte) ([]byte, error)
// Scan returns all rows with keys in range [start, limit). If limit is "",
@@ -24,16 +23,26 @@
// Concurrency semantics: It is legal to perform writes concurrently with
// Scan. The returned stream may or may not reflect subsequent writes to keys
// not yet reached by the stream.
+ //
+ // It is safe to modify the contents of the arguments after Scan returns.
Scan(start, limit []byte) Stream
}
// StoreWriter writes data to a CRUD-capable storage engine.
type StoreWriter interface {
// Put writes the given value for the given key.
+ //
+ // WARNING: For performance reasons, a Put inside a transaction doesn't make
+ // a defensive copy of the value. The client MUST keep the value unchanged
+ // until the transaction commits or aborts.
+ //
+ // It is safe to modify the contents of the key after Put returns.
Put(key, value []byte) error
// Delete deletes the entry for the given key.
// Succeeds (no-op) if the given key is unknown.
+ //
+ // It is safe to modify the contents of the key after Delete returns.
Delete(key []byte) error
}
