Magento 2 – Add Filter or Join Query in Grid Collection

I find a solution. I hope this can help you.

Find the row in your ui component js file where is write the item tag with name "component":

<argument name="data" xsi:type="array">
        <item name="js_config" xsi:type="array">
            <item name="component" xsi:type="string">Magento_Ui/js/grid/provider</item>
        </item>
    </argument>

and change it like:

 <argument name="data" xsi:type="array">
        <item name="js_config" xsi:type="array">
            <item name="component" xsi:type="string">YourVendor_YourModule/js/grid/provider</item>
        </item>
    </argument>

The path of that js file is: vendor/magento/module-ui/view/base/web/js/grid/provider.js

So the new path of your new custom js file will be: app/code/YourVendor/YourModule/view/base/web/js/grid/provider.js

Change the method "processData" in the way that let you calculate the total of the price column, for example like this: CHECK MODIFIED CODE COMMENT.JUST CHECK processData function because just changed that function and other function copied from vendor\magento\module-ui\view\base\web\js\grid/provider.js

/**
 * Copyright © 2016 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */

define([
    'jquery',
    'underscore',
    'mageUtils',
    'uiElement',
    'Magento_Ui/js/modal/alert',
    'mage/translate'
], function ($, _, utils, Element, alert, $t) {
    'use strict';

    return Element.extend({
        defaults: {
            listens: {
                params: 'reload'
            }
        },

        /**
         * Initializes provider component.
         *
         * @returns {Provider} Chainable.
         */
        initialize: function () {
            utils.limit(this, 'reload', 300);
            _.bindAll(this, 'onReload');

            return this._super();
        },

        /**
         * Initializes provider config.
         *
         * @returns {Provider} Chainable.
         */
        initConfig: function () {
            this._super();

            this.setData({
                items: [],
                totalRecords: 0
            });

            return this;
        },

        /**
         *
         * @param {Object} data
         * @returns {Provider} Chainable.
         */
        setData: function (data) {
            data = this.processData(data);

            this.set('data', data);

            return this;
        },

        /**
         * Reloads data with current parameters.
         */
        reload: function () {
            this.trigger('reload');

            if (this.request && this.request.readyState !== 4) {
                this.request.abort();
            }

            this.request = $.ajax({
                url: this['update_url'],
                method: 'GET',
                data: this.get('params'),
                dataType: 'json'
            });

            this.request
                .done(this.onReload)
                .error(this.onError);
        },

        /* START MODIFIED CODE */
        processData: function (data) {
        var items = data.items;
        var total = 0;
        _.each(items, function (record, index) {
            record._rowIndex = index;
         total += parseFloat(record.price);//price is column of custom table
        });
        jQuery("#custom_total_value").text(total);
        return data;
    }, 
        /* END MODIFIED CODE */
        /**
         * Handles reload error.
         */
        onError: function (xhr) {
            if (xhr.statusText === 'abort') {
                return;
            }

            alert({
                content: $t('Something went wrong.')
            });
        },

        /**
         * Handles successful data reload.
         *
         * @param {Object} data - Retrieved data object.
         */
        onReload: function (data) {
            this.setData(data)
                .trigger('reloaded');
        }
    });
});

record is an object inside the collection which is printed in the grid.

After you can add a block in your layout file:

 <referenceContainer name="content">
        <uiComponent name="your_listing"/>
        <block class="Magento\Framework\View\Element\Template" template="YourVendor_YourModuke::custom_total.phtml" />
    </referenceContainer>

Inside custom_total.phtml I write:

<span><b>Total</b></span> <span id="custom_total_value"></span>

So I can see a row down the grid where is printed the total.

To see the changes in the grid remove all static file and cache with the command:

rm -rf var/cache/* var/page_cache/* var/view_preprocessed/* pub/static/*

inside your root magento directory.

Then recompile static content:

php bin/magento setup:static-content:deploy your_language

EDIT: Alternatively you can modify data object returned by processData method, adding another record with same attributes of a normal record but with totals as values. In this way probably you can have a new row inside the grid. I didn't try this solution but I think it will work.

In your app/code/Test/Testimonial/view/adminhtml/ui_component/testimonial_blog_listing.xml

add in the column tag the class attribute:

 <column name="nameofyourcolumn" class="YourVendor\YourModule\Ui\Component\Listing\Column\MyColumn">

MyColumn class is:

<?php

namespace YourVendor\YourModule\Ui\Component\Listing\Column;

use Magento\Ui\Component\Listing\Columns\Column;

use Magento\Framework\DataObject;
use Magento\Framework\View\Element\UiComponent\ContextInterface;
use Magento\Framework\View\Element\UiComponentFactory;

class MyColumn extends Column{

    public function __construct(
        ContextInterface $context,
        UiComponentFactory $uiComponentFactory,
        \Magento\Backend\Model\Auth\Session $authSession,
        array $components = [],
        array $data = []
    ) {
        if(!in_array(1,$authSession->getUser()->getRoles())){
            $data = [];
        }
        parent::__construct($context, $uiComponentFactory,$components, $data);
    }

}

in your case YourVendor/YourModule is equal to Test/Testimonial

in the $authSession variable you have all information about the authenticated user. In the if which you can read above, I want that if the authenticated user is not an administrator (1 is the ID of the administrators group for me) don't show the column. To achieve this I put an empty array in $data variable, which contains all data printed in the column, as result I don't see anymore the column.