generatelookup.js

#!/usr/bin/env node
// ./generatelookup -l lookupkey -p somekey* -a attribute
var redis = require('redis').createClient();
var async = require('async');
var opt = require('optimist');
opt.usage('$0 -l lookup -p pattern -a attribute');
opt.demand(['l', 'p', 'a']);
var argv = opt.argv;

var iter = '0';

async.doWhilst(
    function (acb) {
        console.log('SCAN', iter);
        //scan with the current iterator, matching the given pattern
        redis.send_command('SCAN', [iter, 'MATCH', argv.p], function (err, result) {
            var keys;
            if (err) {
                acb(err);
            } else {
                //update the iterator
                iter = result[0];
                async.each(result[1],
                    //for each key
                    function (key, ecb) {
                        console.log(key);
                        redis.get(key, function (err, result) {
                            var value;
                            if (err) {
                                ecb(err);
                            } else {
                                //find the attribute in the result and set the lookup
                                value = JSON.parse(result);
                                console.log("Setting lookup:", value[argv.a], key);
                                redis.hset(argv.l, value[argv.a], key, function (err) {
                                    ecb(err);
                                });
                            }
                        });
                    },
                    function (err) {
                        //done with this scan iterator; on to the next
                        acb(err);
                    }
                )
            }
        });
    },
    //test to see if iterator is done
    function () { return iter != '0'; },
    //done
    function (err) {
        if(err) {
            console.log("Error:", err);
        } else {
            console.log("Done.");
        }
        redis.end();
    }
);

generatelookup.lua

--EVAL "this script" lookup-hash pattern attribute
--this script WILL NOT RUN, because SCAN is not deterministic
local lookup = KEYS[1];
local pattern, attr = unpack(ARGV);

local iter = '0';
while true do
    local scan = redis.call('SCAN', iter, 'MATCH', pattern);
    iter = scan[1];
    for idx, keyname in ipairs(scan[2]) do
        local value = cjson.decode(redis.call('GET', keyname));
        redis.call('HSET', lookup, value[attr], keyname);
    end
    if (iter == '0') then
        break;
    end
end