docs(toolkit): cross-reference account-trace key layout

Author: halibobo1205

chainbase/src/main/java/org/tron/core/store/AccountTraceStore.java

@@ -29,6 +29,9 @@ private long xor(long l) {
     return l ^ Long.MAX_VALUE;
   }
 
+  // NOTE: the composite key layout (address || Longs.toByteArray(
+  // number ^ Long.MAX_VALUE)) is also reconstructed in plugins
+  // DbLite#trimExtraHistory. Keep them in sync.
   public void recordBalanceWithBlock(byte[] address, long number, long balance) {
 //    Pair<Long, Long> pair = getPrevBalance(address, number);
 //    logger.info("recordBalanceWithBlock===== address:{} number:{} balance:{}", StringUtil.encode58Check(address), number, balance);

plugins/src/main/java/common/org/tron/plugins/DbLite.java

@@ -558,6 +558,7 @@ private void trimExtraHistory(String liteDir, BlockNumInfo blockNumInfo)
                   .map(BalanceContract.TransactionBalanceTrace.Operation::getAddress)
                   .distinct()
                   .map(ByteString::toByteArray)
+                  // Must match AccountTraceStore#recordBalanceWithBlock key layout.
                   .map(address -> Bytes.concat(address, Longs.toByteArray(
                       blockNum ^ Long.MAX_VALUE)))
                   .forEach(accountTraceDb::delete);