cli: limit flag for debug range-data / debug keys

There was a teasing maxResults field already, completely unused.

Release note: None

pkg/cli/cliflags/flags.go

@@ -885,6 +885,11 @@ Exclusive end key and format as [<format>:]<key>. Supported formats: raw, hex,
 human, rangeID. The raw format supports escaped text. For example, "raw:\x01k"
 is the prefix for range local keys. The hex format takes an encoded MVCCKey.`}
 
+	Limit = FlagInfo{
+		Name:        "limit",
+		Description: `Maximum number of keys to return.`,
+	}
+
 	Values = FlagInfo{
 		Name:        "values",
 		Description: `Print values along with their associated key.`,

pkg/cli/context.go

@@ -307,7 +307,7 @@ var debugCtx struct {
 	inputFile         string
 	ballastSize       base.SizeSpec
 	printSystemConfig bool
-	maxResults        int64
+	maxResults        int
 }
 
 // startCtx captures the command-line arguments for the `start` command.

pkg/cli/debug.go

@@ -202,7 +202,15 @@ func runDebugKeys(cmd *cobra.Command, args []string) error {
 		}
 	}
 
-	return db.Iterate(debugCtx.startKey.Key, debugCtx.endKey.Key, printer)
+	results := 0
+	return db.Iterate(debugCtx.startKey.Key, debugCtx.endKey.Key, func(kv storage.MVCCKeyValue) (bool, error) {
+		done, err := printer(kv)
+		if done || err != nil {
+			return done, err
+		}
+		results++
+		return results == debugCtx.maxResults, nil
+	})
 }
 
 func runDebugBallast(cmd *cobra.Command, args []string) error {
@@ -292,7 +300,8 @@ func runDebugRangeData(cmd *cobra.Command, args []string) error {
 
 	iter := rditer.NewReplicaDataIterator(&desc, db, debugCtx.replicated, false /* seekEnd */)
 	defer iter.Close()
-	for ; ; iter.Next() {
+	for i := 0; ; iter.Next() {
+		i++
 		if ok, err := iter.Valid(); err != nil {
 			return err
 		} else if !ok {
@@ -302,6 +311,9 @@ func runDebugRangeData(cmd *cobra.Command, args []string) error {
 			Key:   iter.Key(),
 			Value: iter.Value(),
 		})
+		if i == debugCtx.maxResults {
+			break
+		}
 	}
 	return nil
 }

pkg/cli/flags.go

@@ -697,12 +697,14 @@ func init() {
 		f := debugKeysCmd.Flags()
 		VarFlag(f, (*mvccKey)(&debugCtx.startKey), cliflags.From)
 		VarFlag(f, (*mvccKey)(&debugCtx.endKey), cliflags.To)
+		IntFlag(f, &debugCtx.maxResults, cliflags.Limit, 0)
 		BoolFlag(f, &debugCtx.values, cliflags.Values, debugCtx.values)
 		BoolFlag(f, &debugCtx.sizes, cliflags.Sizes, debugCtx.sizes)
 	}
 	{
 		f := debugRangeDataCmd.Flags()
 		BoolFlag(f, &debugCtx.replicated, cliflags.Replicated, debugCtx.replicated)
+		IntFlag(f, &debugCtx.maxResults, cliflags.Limit, 0)
 	}
 	{
 		f := debugGossipValuesCmd.Flags()