query/parse out all /mydb/_local keys in your couchdb data file

query_local.js

var fs = require('fs')

var rs = fs.createReadStream(PATH TO YOUR DATABASE FILE.couch)

var match = new Buffer('_local/')
var matchi = 0

rs.on('data',function(b){
   for(var i=0;i<b.length;++i) bite(b,i)
})

var state = 'out'
var id =[]

var equals = '='.charCodeAt(0)

var processed = 0


function bite(buf,i){
  processed++
  if(state === 'out') {
    //console.log(matchi)
    if(buf[i] === match[matchi]){
      matchi++
    } else if(buf[i] === match[0]){
      matchi = 1
    } else {
      matchi = 0
    }

    if(matchi === match.length){
      state = 'in'
      matchi = 0
    }
  } else {
    if(id.length === 100 || buf[i] === 0){
      // remove
      id = new Buffer(id)
      id = id.slice(0,id.lastIndexOf('h'.charCodeAt(0)))
      if(id.lastIndexOf(2) > -1){
        id = id.slice(0,id.lastIndexOf(2)-1)
      }
      state = 'out'
      process.stdout.write(JSON.stringify('_local/'+id)+'\n')
      id = []
    } else {
      id.push(buf[i])
    }
  }
}