code: private function setDefaultValue($columnDefault)
      {
          if (is_null($columnDefault)) {
              $this->defaultValue = '';
          } else {
              switch ($this->type) {
                  case 'character':
                  case 'character varying':
                  case 'text':
                      // formatted like 'default'::text
                  case 'USER-DEFINED':
                      // formatted like 'default'::tableName_columnName
                      // parse out default
                      $parseColumnDefault = explode("'", $columnDefault);
                      $this->defaultValue = $parseColumnDefault[1];
                      break;
                  case 'boolean':
                      // overwrite to be congruous with a postgres value returned from select
                      if ($columnDefault == 'true') {
                          $this->defaultValue = Postgres::BOOLEAN_TRUE;
                      }
                      break;
                  default:
                      $this->defaultValue = $columnDefault;
              }
          }
      }
docs: input can be null