mongo/jstests/core/index_bigkeys.js

t = db.bigkeysidxtest;

var keys = []

var str = "aaaabbbbccccddddeeeeffffgggghhhh";

while ( str.length < 20000 ) {
    keys.push( str );
    str = str + str;
}

function doInsert( order ) {
    if (order == 1) {
        for (var i = 0; i < 10; i++) {
            t.insert({ _id: i, k: keys[i] });
        }
    }
    else {
        for (var i = 9; i >= 0; i--) {
            t.insert({ _id: i, k: keys[i] });
        }
    }
}

var expect = null;

function check() {
    assert(t.validate().valid);
    assert.eq( 5, t.count() );

    var c = t.find({ k: /^a/ }).count();
    assert.eq( 5, c );
}

function runTest( order ) {
    t.drop();
    t.ensureIndex({ k: 1 });
    doInsert( order );
    check(); // check incremental addition

    t.reIndex();
    check(); // check bottom up

    t.drop();
    doInsert( order );
    assert.eq( 1, t.getIndexes().length );
    t.ensureIndex({ k: 1 });
    assert.eq( 1, t.getIndexes().length );

    t.drop();
    doInsert( order );
    assert.eq( 1, t.getIndexes().length );
    t.ensureIndex({ k: 1 }, { background: true });
    assert.eq( 1, t.getIndexes().length );
}

runTest( 1 );
runTest( 2 );