improve performance of cast$expr

[Uzlopak]

Dont know if this is improving the overall performance, but should I improved some parts.

omitUndefined is now about 5 - 10 % faster
isPath is now about 40 % faster.

Benchmarks and their result:

'use strict';

const Benchmark = require('benchmark');


function omitUndefinedVar1(val) {
  const keys = Object.keys(val);
  for (const key of keys) {
    if (val[key] === void 0) {
      delete val[key];
    }
  }
}

function omitUndefinedVar2(val) {
  const keys = Object.keys(val);
  for (let i = 0, len = keys.length; i < len; ++i) {
    (val[keys[i]] === void 0) && delete val[keys[i]];
  }
}

new Benchmark.Suite()
.add('var1 valid', function () {
  const a = omitUndefinedVar1({
    a: undefined,
    b: null,
    c: undefined,
    d: 'a',
    fa: 234,
    ferfe:234234,
    adcverg:234234
  })
})
.add('var1 valid2', function () {
  const a = omitUndefinedVar1({
    d: 'a',
    fa: 234,
    ferfe:234234,
    adcverg:234234
  })
})
  .add('var2 valid', function () {
    const a = omitUndefinedVar2({
      a: undefined,
      b: null,
      c: undefined,
      d: 'a',
      fa: 234,
      ferfe:234234,
      adcverg:234234
    })
  })
  .add('var2 valid2', function () {
    const a = omitUndefinedVar2({
      d: 'a',
      fa: 234,
      ferfe:234234,
      adcverg:234234
    })
  })
  .on('cycle', function (evt) {
    if (process.env.MONGOOSE_DEV || process.env.PULL_REQUEST) {
      console.log(String(evt.target));
    }
  })
  .run();
process.memoryUsage();

// --trace-opt --trace-deopt --trace-bailout

MONGOOSE_DEV=1 node omitUndefined.js
var1 valid x 1,925,657 ops/sec ±0.56% (93 runs sampled)
var1 valid2 x 19,595,175 ops/sec ±2.95% (90 runs sampled)
var2 valid x 2,026,454 ops/sec ±0.30% (95 runs sampled)
var2 valid2 x 21,847,207 ops/sec ±0.43% (90 runs sampled)

'use strict';

const Benchmark = require('benchmark');

function isPathVar1(val) {
  return typeof val === 'string' && val.startsWith('$');
}
function isPathVar2(val) {
  return typeof val === 'string' && val[0] === '$';
}
function isPathVar3(val) {
  return typeof val === 'string' && val.charCodeAt(0) === 36;
}
function isPathVar4(val) {
  return typeof val === 'string' && val.charCodeAt() === 36;
}
function isPathVar5(val) {
  return typeof val === 'string' && val.charAt() === '$';
}
new Benchmark.Suite()
  .add('var1 valid', function () {
    const a = isPathVar1('$aasdasdf')
  })
  .add('var1 invalid', function () {
    const a = isPathVar1('aasdasdf')
  })
  .add('var2 valid', function () {
    const a = isPathVar2('$aasdasdf')
  })
  .add('var2 invalid', function () {
    const a = isPathVar2('aasdasdf')
  })
  .add('var3 valid', function () {
    const a = isPathVar3('$aasdasdf')
  })
  .add('var3 invalid', function () {
    const a = isPathVar3('aasdasdf')
  })
  .add('var4 valid', function () {
    const a = isPathVar4('$aasdasdf')
  })
  .add('var4 invalid', function () {
    const a = isPathVar4('aasdasdf')
  })
  .add('var5 valid', function () {
    const a = isPathVar5('$aasdasdf')
  })
  .add('var5 invalid', function () {
    const a = isPathVar5('aasdasdf')
  })
  .on('cycle', function (evt) {
    if (process.env.MONGOOSE_DEV || process.env.PULL_REQUEST) {
      console.log(String(evt.target));
    }
  })
  .run();
process.memoryUsage();

// --trace-opt --trace-deopt --trace-bailout

MONGOOSE_DEV=1 node isPath.js
var1 valid x 894,729,315 ops/sec ±2.38% (85 runs sampled)
var1 invalid x 901,086,157 ops/sec ±2.30% (84 runs sampled)
var2 valid x 1,373,966,160 ops/sec ±0.21% (95 runs sampled)
var2 invalid x 1,376,078,120 ops/sec ±0.13% (93 runs sampled)
var3 valid x 914,513,098 ops/sec ±2.31% (86 runs sampled)
var3 invalid x 902,081,446 ops/sec ±2.33% (85 runs sampled)
var4 valid x 906,717,792 ops/sec ±2.29% (84 runs sampled)
var4 invalid x 914,859,437 ops/sec ±2.32% (86 runs sampled)
var5 valid x 523,148,950 ops/sec ±6.62% (87 runs sampled)
var5 invalid x 136,384,194 ops/sec ±3.14% (84 runs sampled)

Variant 2 is the chosen one. We should not use startsWith when we only want to check if the first character is a specific one.

[vkarpov15]

Thanks 👍