cmd/geth: add db-command to inspect freezer index (#22633)

This PR makes it easier to inspect the freezer index, which could be useful to investigate things like #22111

core/rawdb/freezer.go

@@ -118,7 +118,7 @@ func newFreezer(datadir string, namespace string, readonly bool) (*freezer, erro
 		trigger:      make(chan chan struct{}),
 		quit:         make(chan struct{}),
 	}
-	for name, disableSnappy := range freezerNoSnappy {
+	for name, disableSnappy := range FreezerNoSnappy {
 		table, err := newTable(datadir, name, readMeter, writeMeter, sizeGauge, disableSnappy)
 		if err != nil {
 			for _, table := range freezer.tables {

core/rawdb/freezer_table.go

@@ -636,25 +636,24 @@ func (t *freezerTable) Sync() error {
 	return t.head.Sync()
 }
 
-// printIndex is a debug print utility function for testing
-func (t *freezerTable) printIndex() {
+// DumpIndex is a debug print utility function, mainly for testing. It can also
+// be used to analyse a live freezer table index.
+func (t *freezerTable) DumpIndex(start, stop int64) {
 	buf := make([]byte, indexEntrySize)
 
-	fmt.Printf("|-----------------|\n")
-	fmt.Printf("| fileno | offset |\n")
-	fmt.Printf("|--------+--------|\n")
+	fmt.Printf("| number | fileno | offset |\n")
+	fmt.Printf("|--------|--------|--------|\n")
 
-	for i := uint64(0); ; i++ {
+	for i := uint64(start); ; i++ {
 		if _, err := t.index.ReadAt(buf, int64(i*indexEntrySize)); err != nil {
 			break
 		}
 		var entry indexEntry
 		entry.unmarshalBinary(buf)
-		fmt.Printf("|  %03d   |  %03d   | \n", entry.filenum, entry.offset)
-		if i > 100 {
-			fmt.Printf(" ... \n")
+		fmt.Printf("|  %03d   |  %03d   |  %03d   | \n", i, entry.filenum, entry.offset)
+		if stop > 0 && i >= uint64(stop) {
 			break
 		}
 	}
-	fmt.Printf("|-----------------|\n")
+	fmt.Printf("|--------------------------|\n")
 }

core/rawdb/freezer_table_test.go

@@ -525,7 +525,7 @@ func TestOffset(t *testing.T) {
 
 		f.Append(4, getChunk(20, 0xbb))
 		f.Append(5, getChunk(20, 0xaa))
-		f.printIndex()
+		f.DumpIndex(0, 100)
 		f.Close()
 	}
 	// Now crop it.
@@ -572,7 +572,7 @@ func TestOffset(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		f.printIndex()
+		f.DumpIndex(0, 100)
 		// It should allow writing item 6
 		f.Append(numDeleted+2, getChunk(20, 0x99))
 

core/rawdb/schema.go

@@ -114,9 +114,9 @@ const (
 	freezerDifficultyTable = "diffs"
 )
 
-// freezerNoSnappy configures whether compression is disabled for the ancient-tables.
+// FreezerNoSnappy configures whether compression is disabled for the ancient-tables.
 // Hashes and difficulties don't compress well.
-var freezerNoSnappy = map[string]bool{
+var FreezerNoSnappy = map[string]bool{
 	freezerHeaderTable:     false,
 	freezerHashTable:       true,
 	freezerBodiesTable:     false,