kvserver: add some TODOs about future renames, clarify some comments

Epic: CRDB-220
Release note: None

pkg/kv/kvserver/app_batch.go

@@ -24,6 +24,10 @@ import (
 )
 
 type appBatchStats struct {
+	// TODO(sep-raft-log):
+	// numEntries
+	// numEntriesBytes
+	// numEntriesEmpty
 	numMutations             int
 	numEntriesProcessed      int
 	numEntriesProcessedBytes int64

pkg/kv/kvserver/apply/task.go

@@ -71,6 +71,10 @@ var ErrRemoved = errors.New("replica removed")
 type EphemeralBatch interface {
 	// Stage inserts a Command into the Batch. In doing so, the Command is
 	// checked for rejection and a CheckedCommand is returned.
+	//
+	// TODO(tbg): consider renaming this to Add, so that in implementations
+	// of this we less unambiguously refer to "staging" commands into the
+	// pebble batch.
 	Stage(context.Context, Command) (CheckedCommand, error)
 	// Close closes the batch and releases any resources that it holds.
 	Close()

pkg/kv/kvserver/replica_app_batch.go

@@ -124,6 +124,10 @@ func (b *replicaAppBatch) Stage(
 		return nil, err
 	}
 
+	// TODO(tbg): if we rename Stage to Add we could less ambiguously
+	// use the verb "stage" instead of "add" for all of the methods
+	// below.
+
 	if err := b.runPreAddTriggersReplicaOnly(ctx, cmd); err != nil {
 		return nil, err
 	}
@@ -197,8 +201,6 @@ func (b *replicaAppBatch) runPreAddTriggersReplicaOnly(
 // staged in the replicaAppBatch's write batch.
 //
 // May mutate `cmd`.
-//
-// All errors from this method are fatal for this Replica.
 func (b *replicaAppBatch) runPostAddTriggersReplicaOnly(
 	ctx context.Context, cmd *replicatedCmd,
 ) error {

pkg/kv/kvserver/replica_application_state_machine.go

@@ -44,7 +44,7 @@ import (
 // TODO(ajwerner): add metrics to go with these stats.
 type applyCommittedEntriesStats struct {
 	appBatchStats
-	numBatchesProcessed  int
+	numBatchesProcessed  int // TODO(sep-raft-log): numBatches
 	stateAssertions      int
 	numConfChangeEntries int
 }