test leveldb keys prefix search with a large dict.

leveldb-keys-prefix-search.js

var levelup = require('levelup')

// open a data store
var db = levelup('/tmp/foo.leveldb')
var list = [];
var start = new Date().getTime();
var prefix = "ha";
//cat /usr/share/dict/words | grep "^ha" | wc
db.createReadStream({
    start: prefix, // jump to first key with the prefix
    end: prefix + "\xFF" // stop at the last key with the prefix
})
.on('data', function(data) {
    list.push(data.key);
    // console.log(data)
})
.on('error', function() {
    console.log('error', arguments)
})
.on('close', function() {
    console.log('close', list, list.length, (new Date().getTime()) - start)
});

//ref //http://dailyjs.com/2013/05/03/leveldb-and-node-2/

Before that, /tmp/foo.leveldb stored all words in Mac OSX's /usr/share/dict/words. The key and the value is the same word.

Leveldb keys prefix search is fast enough to do a word auto-suggestion.

cat /usr/share/dict/words | grep "^ha" | wc
grep is really fast ,too!