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Search - "mysql murder"
I’m surrounded by idiots.
I’m continually reminded of that fact, but today I found something that really drives that point home.
Gather ‘round, everybody, it’s story time!
While working on a slow query ticket, I perused the code, finding several causes, and decided to run git blame on the files to see what dummy authored the mental diarrhea currently befouling my screen. As it turns out, the entire feature was written by mister legendary Apple golden boy “Finder’s Keeper” dev himself.
To give you the full scope of this mess, let me start at the frontend and work my way backward.
This function allows the user to better see the rows in the API Calls table, for which there is a also search feature — the very thing I’m tasked with fixing.
It’s worth noting that above the search feature are two inputs for a date range, with some helpful links like “last week” and “last month” … and “All”. It’s also worth noting that this table is for displaying search results of all the API requests and their responses for a given merchant… this table is enormous.
This search field for this table queries the backend on every character the user types. There’s no debouncing, no submit event, etc., so it triggers on every keystroke. The actual request runs through a layer of abstraction to parse out and log the user-entered date range, figure out where the request came from, and to map out some column names or add additional ones. It also does some hard to follow (and amazingly not injectable) orm condition building. It’s a mess of functional ugly.
The important columns in the table this query ultimately searches are not indexed, despite it only looking for “create_order” records — the largest of twenty-some types in the table. It also uses partial text matching (again: on. every. single. keystroke.) across two varchar(255)s that only ever hold <16 chars — and of which users only ever care about one at a time. After all of this, it filters the results based on some uncommented regexes, and worst of all: instead of fetching only one page’s worth of results like you’d expect, it fetches all of them at once and then discards what isn’t included by the paginator. So not only is this a guaranteed full table scan with partial text matching for every query (over millions to hundreds of millions of records), it’s that same full table scan for every single keystroke while the user types, and all but 25 records (user-selectable) get discarded — and then requeried when the user looks at the next page of results.
What the bloody fucking hell? I’d swear this idiot is an intern, but his code does (amazingly) actually work.
No wonder this search field nearly crashed one of the servers when someone actually tried using it.