wdb-migrations: add block time cache.

lib/wallet/migrations.js

@@ -11,6 +11,7 @@ const Logger = require('blgr');
 const bdb = require('bdb');
 const bio = require('bufio');
 const {BufferSet} = require('buffer-map');
+const LRU = require('blru');
 const HDPublicKey = require('../hd/public');
 const binary = require('../utils/binary');
 const {encoding} = bio;
@@ -808,6 +809,8 @@ class MigrateTXCountTimeIndex extends AbstractMigration {
     this.unconfirmedBatchSize = 1000;
 
     this.UNCONFIRMED_HEIGHT = 0xffffffff;
+
+    this.blockTimeCache = new LRU(50);
   }
 
   /**
@@ -1101,6 +1104,10 @@ class MigrateTXCountTimeIndex extends AbstractMigration {
       return null;
 
     const rawPath = await this.ldb.get(this.layout.wdb.P.encode(wid, hash));
+
+    if (!rawPath)
+      return null;
+
     const account = encoding.readU32(rawPath, 0);
     return account;
   }
@@ -1128,13 +1135,20 @@ class MigrateTXCountTimeIndex extends AbstractMigration {
 
   async getMedianTime(height) {
     const getBlockTime = async (height) => {
+      const cache = this.blockTimeCache.get(height);
+
+      if (cache != null)
+        return cache;
+
       const data = await this.ldb.get(this.layout.wdb.h.encode(height));
 
       if (!data)
         return null;
 
       const time = encoding.readU64(data, 32);
 
+      this.blockTimeCache.set(height, time);
+
       return time;
     };
 

test/util/migrations.js

@@ -235,7 +235,7 @@ exports.dumpChainDB = async (chaindb, prefixes) => {
  * @param {Boolean} options.throw - throw on error.
  * @param {Boolean} options.bail - bail on first error.
  * @param {Boolean} options.logErrors - log errors.
- * @returns {Promise<[]String>} - errors.
+ * @returns {Promise<String[]>} - errors.
  */
 
 exports.checkEntries = async (ldb, options) => {