Adding mysql indices

[enyachoke]

I needed to be able to set index optimizations for mysql so I created this block

class CreateIndexBlock extends Squel.cls.Block {

  addIndexDirectives(directives) {
    let column = '';
    for (const directive of directives) {
      column = column + ` ${directive.type.toUpperCase()} INDEX ${this._buildJoinFor(directive.for)} ${this._buildIndexList(directive.index_list)}`;
    }
    this._column = column;
  }

  _toParamString() {
    return {
      text: this._column || '',
      values: [],
    };
  }

  _buildIndexList(list) {
    return `(${list.join()})`;
  }

  _buildJoinFor(value) {
    let joinFor = ''
    if (!this._isEmpty(value)) {
      joinFor = `FOR ${value.toUpperCase()}`
    }
    return joinFor;
  }

  _isEmpty(val) {
    if (val === undefined)
      return true;

    if (typeof (val) == 'function' || typeof (val) == 'number' || typeof (val) == 'boolean' || Object.prototype.toString.call(val) === '[object Date]')
      return false;

    if (val == null || val.length === 0) // null or 0 length array
      return true;

    if (typeof (val) == "object") {
      // empty object

      var r = true;

      for (var f in val)
        r = false;

      return r;
    }

    return false;
  }

Then added custom select using this block

Squel.myselect = function (options) {
      return Squel.select(options, [
        new Squel.cls.StringBlock(options, 'SELECT'),
        new Squel.cls.FunctionBlock(options),
        new Squel.cls.DistinctBlock(options),
        new Squel.cls.GetFieldBlock(options),
        new Squel.cls.FromTableBlock(options),
        new CreateIndexBlock(options),
        new Squel.cls.JoinBlock(options),
        new Squel.cls.WhereBlock(options),
        new Squel.cls.GroupByBlock(options),
        new Squel.cls.HavingBlock(options),
        new Squel.cls.OrderByBlock(options),
        new Squel.cls.LimitBlock(options),
        new Squel.cls.OffsetBlock(options),
        new Squel.cls.UnionBlock(options),
      ]);
    }

Is this worthy having in core?