[SmartCrawl Pro] Errors in Error log

Following is the sample of error I find in Error log

[07-Jan-2019 15:53:00 UTC] PHP Warning: preg_match(): Compilation failed: invalid range in character class at offset 4 in /home/indcara8/public_html/wp-content/plugins/wpmu-dev-seo/includes/external/simple_html_dom.php on line 1364

[07-Jan-2019 16:06:26 UTC] PHP Warning: Invalid argument supplied for foreach() in /home/indcara8/public_html/wp-content/plugins/wpmu-dev-seo/includes/external/simple_html_dom.php on line 691

[07-Jan-2019 03:41:40 UTC] WordPress database error Deadlock found when trying to get lock; try restarting transaction for query DELETE FROM `ua5_options` WHERE `option_name` = '_site_transient_wdp_un_local_projects' made by do_action('admin_init':wink:, WP_Hook->do_action, WP_Hook->apply_filters, WPMUDEV_Dashboard_Site->compatibility_warnings, WPMUDEV_Dashboard_Site->is_upfront_theme_installed, WPMUDEV_Dashboard_Site->get_cached_projects, WPMUDEV_Dashboard_Site->get_transient, get_site_transient, delete_site_option, delete_network_option, delete_option

Disabled the WPMUDEV dashboard plugin for now. Not sure if that is the reason. Please provide solutions to each of the above errors.

  • Adam Czajczyk
    • Support Gorilla

    Hello Dinesh

    I hope you’re well today and thank you for your question!

    I assume that you’re running the site on PHP 7.3.x, right? The first two errors are related to the the PHP version and our developers are already aware of it. They’re preparing the fix and it should be released with one of the nearest plugin updates so please keep SmartCrawl up to date and it should solve the issue.

    As for the third error. This is a bit more complex. The database “deadlock” basically means that two or more routines are trying to use the same database table at the very same time. That shouldn’t be happening as the queries should be “queued” but sometimes that fails and the “deadlock” occurs. In case of WordPress it’s rarely cased by the single plugin but rather but issues like for example: some plugin conflict, some malfunctioning caching system (either a plugin or some cache on server) or a broken server-side cache content, it might be the consequence of some db error that occurred in the past and left the tables “broken” and so on.

    We’d need to check this, therefore. You mentioned that once you disabled the WPMU DEV Dashboard plugin this stopped showing up. However, apart from showing in logs I think it didn’t affect site features, right? Would you be able to enable WPMU DEV Dashboard again and grant me a support access to the site so I could just take a look at its configuration? You can enable support access by clicking on “Grant support access” button on “WPMU DEV -> Support” page in site’s back-end. Just let me know here once it’s done, please.

    Once I checked this, we’ll then decide what has to be done next to find the cause of that deadlock and to fix it.

    Best regards,


  • Adam Czajczyk
    • Support Gorilla

    Hi Dinesh

    Thanks for granting access.

    I checked the site and I’d suggest starting with a simple change. I noticed that you’re hosting on SiteGround and using their SGOptimizer while using Hummingbird at the same time. That’s fine but since there seems to be SG dynamic cache enabled while Hummingbird’s Page Cache is enabled as well, this can lead to some unexpected issues as the caches are overlapping at some points.

    In theory, that kind of cache shouldn’t affect the database much but it often does and I can tell from the experience of multiple cases that with SG it’s, unfortunately, too often.

    The point is to use just one caching solution so I’d start with this: clear SG dynamic cache and disable it on server, then clear HB caches through “Hummingbird -> Dashboard” page -> “Clear cache” button. After that, also go to the Hummingbird -> Advanced Tools -> Database cleanup and use it to clear all transient.

    After that, keep watching the log if the “deadlock” or similar db error keeps occurring. The good news is that the error refers to the WP transient cache so it doesn’t really affect anything much, except causing the database to grow bigger and bigger overtime (so the side-effect might be the site getting slower – but shouldn’t be causing any malfunction).

    Give it a go, please, and let me know about results.

    Kind regards,


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