This is a hack on how to get output of which theme function to call to alter each element on page. So you will need to go to In includes/theme.inc in the Drupal 7 theme() function, around line 1161 and change $output from one line to two lines and to have this code below. You will get theme suggestions all around the page, which will be messy but will help you find what you need.

Wanting to add field to some entity (we here pick order entity) by code, for example when deploying to production, use this snippet of code and you will have this new field added.

I finally converted this old blog from drupal 6 to drupal 8. Good starting point is this page
https://www.drupal.org/docs/8/upgrade/upgrading-from-drupal-6-or-7-to-d…

Maybe you will stumble upon some site or service that will still serve XML and not JSON. TO fix this to your most liked format use this on that XML string

For debugging purposes I need to clear cache for particular drupal commerce order, but this can be done for any entity, just replace table name and id's in code below

 $table = 'cache_entity_commerce_order';
 $id ="776764";
 cache_clear_all($id, $table);

Here is nice little snippet I use when I need to list all or some of the products from drupal commerce in select field in some forms, for example entity form.
 

To delete stale CSS and JS files from server, you need to add

variable_set('drupal_stale_file_threshold', 86400);

to your settings.php and change the value from default 30 days (2592000) to for example 1 day above.
They will be deleted on cron run.

Run this in terminal

drush php-eval "drush_print_r(db_select('system', 's') ->fields('s', array('weight')) ->condition('name', 'some_module', '=') ->execute() ->fetchField())";

and then when you get the required modules weight, change it with

Caching per block can be quite useful, depending on how much blocks you have in page, but odds are you are going to have some in footer and header.

Just go and run this into devel/php

db_query("update elysia_cron set running = 0 where name = 'search_cron'");

where in this case I am unstucking cron job for search indexing.