core: track and improve tx indexing/unindexing (#21331)

* core: add background indexer to waitgroup

* core: make indexer stopable

* core/rawdb: add unit tests

* core/rawdb: fix lint

* core/rawdb: fix tests

* core/rawdb: fix linter

core/rawdb/chain_iterator_test.go

@@ -20,6 +20,7 @@ import (
 	"math/big"
 	"reflect"
 	"sort"
+	"sync"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -59,7 +60,7 @@ func TestChainIterator(t *testing.T) {
 	}
 	for i, c := range cases {
 		var numbers []int
-		hashCh, _ := iterateTransactions(chainDb, c.from, c.to, c.reverse)
+		hashCh := iterateTransactions(chainDb, c.from, c.to, c.reverse, nil)
 		if hashCh != nil {
 			for h := range hashCh {
 				numbers = append(numbers, int(h.number))
@@ -80,3 +81,85 @@ func TestChainIterator(t *testing.T) {
 		}
 	}
 }
+
+func TestIndexTransactions(t *testing.T) {
+	// Construct test chain db
+	chainDb := NewMemoryDatabase()
+
+	var block *types.Block
+	var txs []*types.Transaction
+	for i := uint64(0); i <= 10; i++ {
+		if i == 0 {
+			block = types.NewBlock(&types.Header{Number: big.NewInt(int64(i))}, nil, nil, nil, newHasher()) // Empty genesis block
+		} else {
+			tx := types.NewTransaction(i, common.BytesToAddress([]byte{0x11}), big.NewInt(111), 1111, big.NewInt(11111), []byte{0x11, 0x11, 0x11})
+			txs = append(txs, tx)
+			block = types.NewBlock(&types.Header{Number: big.NewInt(int64(i))}, []*types.Transaction{tx}, nil, nil, newHasher())
+		}
+		WriteBlock(chainDb, block)
+		WriteCanonicalHash(chainDb, block.Hash(), block.NumberU64())
+	}
+	// verify checks whether the tx indices in the range [from, to)
+	// is expected.
+	verify := func(from, to int, exist bool, tail uint64) {
+		for i := from; i < to; i++ {
+			if i == 0 {
+				continue
+			}
+			number := ReadTxLookupEntry(chainDb, txs[i-1].Hash())
+			if exist && number == nil {
+				t.Fatalf("Transaction indice missing")
+			}
+			if !exist && number != nil {
+				t.Fatalf("Transaction indice is not deleted")
+			}
+		}
+		number := ReadTxIndexTail(chainDb)
+		if number == nil || *number != tail {
+			t.Fatalf("Transaction tail mismatch")
+		}
+	}
+	IndexTransactions(chainDb, 5, 11, nil)
+	verify(5, 11, true, 5)
+	verify(0, 5, false, 5)
+
+	IndexTransactions(chainDb, 0, 5, nil)
+	verify(0, 11, true, 0)
+
+	UnindexTransactions(chainDb, 0, 5, nil)
+	verify(5, 11, true, 5)
+	verify(0, 5, false, 5)
+
+	UnindexTransactions(chainDb, 5, 11, nil)
+	verify(0, 11, false, 11)
+
+	// Testing corner cases
+	signal := make(chan struct{})
+	var once sync.Once
+	indexTransactionsForTesting(chainDb, 5, 11, signal, func(n uint64) bool {
+		if n <= 8 {
+			once.Do(func() {
+				close(signal)
+			})
+			return false
+		}
+		return true
+	})
+	verify(9, 11, true, 9)
+	verify(0, 9, false, 9)
+	IndexTransactions(chainDb, 0, 9, nil)
+
+	signal = make(chan struct{})
+	var once2 sync.Once
+	unindexTransactionsForTesting(chainDb, 0, 11, signal, func(n uint64) bool {
+		if n >= 8 {
+			once2.Do(func() {
+				close(signal)
+			})
+			return false
+		}
+		return true
+	})
+	verify(8, 11, true, 8)
+	verify(0, 8, false, 8)
+}