split_guids.js

// Number of chars of the first two groups (most-significant) in UUID string
var UUIDHeadChars = 12;
// Max number of integers that can be represented using
var UUIDHeadMax = Math.pow(16, UUIDHeadChars);


function UUIDFromInt(num) {
    assert(num < UUIDHeadMax);
    // Format num as hexadecimal string with enough left-zero-padding
    // to reach UUIDHeadChars
    head =
	(('0'.repeat(UUIDHeadChars)) + num.toString(16)).substr(-UUIDHeadChars);
    assert.eq(head.length, UUIDHeadChars);
    // return UUID(HHHHHHHH-HHHH-0000-0000-000000000000)
    return UUID(
	head.substr(0, 8) + '-' + head.substr(8) + '-' +
	'0'.repeat(4) + '-' +
	'0'.repeat(4) + '-' +
	'0'.repeat(12));
};

function genUUIDSplitPoints(numChunks) {
    var splitPoints = [];
    var gap = Math.round(UUIDHeadMax / numChunks);
    var currHead = 0;
    for (var i = 0; i < (numChunks - 1); i++) {
	currHead += gap;
	splitPoints.push(UUIDFromInt(currHead));
    }
    return splitPoints;
};

function chunkInfos(ns) {
    var s = '';
    confDB.chunks.find({ns: ns}).sort({ns: 1, min: 1}).forEach(function(z) {
	s += ' ' + z._id + '  ' + z.shard + '\n\tmin: ' + tojson(z.min) +
	    '\n\tmax: ' + tojson(z.max) + '\n';
    });

    return s;
};

var splitPoints = genUUIDSplitPoints(16);

for (var i = 0; i < splitPoints.length; i++) {
    var splitPt = {_id: {id: splitPoints[i]}};
    sh.splitAt("uuidTest.test", splitPt);
}