Toby's Log

MySQL: DELETE with sub-query on same table

I had an issue with a MySQL query containing a sub-query recently where it worked fine when done as a SELECT query, but gave an error when switching it to a DELETE query. The error given was something like ‘You can’t specify target table “items” for update in FROM clause’. The sub-query was referencing the same table as the main query, which apparently can’t be done directly in MySQL because the table will be modified during deletion. But there is a sort of a hack I found in this StackOverflow answer, among others, to force it to create a temp table and allow it to work.

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Swap file for composer out of memory problems

PHP’s defacto package manager, composer, has long required large amounts of memory to do updates for larger projects, often more than servers or virtual machines have. The script will die with an out of memory error, or more recently, the simple message “Killed”, and do no work in these situations. The normal procedure is to develop locally, deploy local lock file (composer.lock) to the server, and run composer install instead of update. But I’ve recently moved to doing most of my development in VMs, so I have had to work around this problem to get things installed or updated. A swap file is the solution for Linux machines provided in the official docs and expanded in a StackOverflow answer.

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Unprivileged Homebrew install, 2021 edition

On my new MacBook, I’ve been isolating responsibilities into separate user accounts. This includes an unprivileged “manager” account for installing most global third-party software, and a few development accounts for different purposes. I use Homebrew to install some dev related software, but my old Homebrew setup didn’t work with this conceptually, nor with the more locked down privileges of newer Mac OS versions. I didn’t want to give Homebrew or its packages admin or root privileges, so I have adapted Homebrew’s untar anywhere method to install a globally available Homebrew using the unprivileged manager account, only requiring a privileged account briefly. I’ve also used untar anywhere for a per-account Homebrew install to allow each dev account to have custom versions of any desired packages, with no privileged account required.

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jQuery AJAX and multipart form handling

I recently had need to submit a web form with file fields via AJAX. The application uses jQuery and was already submitting forms just fine without file fields using the .serialize() method to pass data to a jQuery.ajax() call. That didn’t seem to handle the file fields, though. Searching the internet, I found a solution using the browser built in FormData object.

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