You can have problems only if database schema changed from older to new version. To know if the your is the case, you can compare the file wp-admin/includes/schema.php for both the versions, see that online here for 3.8.1 and here for 3.5.1. Note that a db index change should not beak the site, but it … Read more
Make a copy of the site in localhost, this will be better approch. To upgrade site see Upgarding WordPress – Extended Instructions
If your plugin customise functionaity of other plugins through hooks (actions and filters) the answer is Yes.
By default WP is very reluctant to show or display any errors. That’s inline with its strategy of “dumbing down” things of sorts. The configuration I use to monitor for errors is along the lines of this in wp-config.php: define( ‘WP_DEBUG’, true ); define( ‘WP_DEBUG_DISPLAY’, false ); @ini_set( ‘display_errors’,’Off’ ); @ini_set( ‘log_errors’,’On’ ); @ini_set( ‘error_log’,’/home/user/logs/php_site_name.log’ … Read more
register_activation_hook() only attaches a function to run on activation of your plugin, not on updating. See the docs for full details, particularly this part: 3.1 : This hook is now fired only when the user activates the plugin and not when an automatic plugin update occurs (#14915). Of course, you could force your hook to … Read more
So after some thinking I came up with this: Codex / WordPress Versions has Changelogs, but these seem to mention (recent) database upgrades implicitly, starting at 5.0. (Compare how Matomo explicitly states DB upgrades). Maybe this will be enough for future versions, here’s the thorough, cumbersome way that works for older versions, too: check db_version … Read more
This was recently discussed at length on the wp-hackers list. Here’s the thread: Will Activation Hook Be Executed During Plugin Upgradation? Quoting Otto from the list: The simplest method that would work everywhere would be simply to store the version number of the plugin somewhere (like in your options entry in the database), then compare … Read more
WP CLI has a command that can upgrade the database: wp core update-db If that command doesn’t upgrade the entire network, you can pass in the site you want upgraded as an additional parameter e.g. wp core update-db –site=”http://example.com/testsite/” You can get WP CLI from here: http://wp-cli.org it’s also available on github You can install … Read more
Was a bug in the core, I published the ticket ( https://core.trac.wordpress.org/ticket/32310 ) and is added for the next version 4.2.3. In this version the code change the collation of some tables and this works fine if the change is fast. But in big tables this change take time, hive a timeout in the upgrade … Read more
If you have access to your files via ftp, you should be able to upgrade WordPress manually. According to WordPress.org, you can do so by swapping out a few folders and files: Step 1: Replace WordPress files Get the latest WordPress zip (or tar.gz) file. Unpack the zip file that you downloaded. Deactivate plugins. Delete … Read more