Searching mysql database with multiple PHP queries instead of OR operator - php

Question

TLDR; I'm trying to get some 'fuzzy' results from a search query that fails to come up with things that are actually there.
The problem:
This specific setup is in Wordpress land, but that's not decisively relevant to the issue. There's this longstanding problem with wordpress search – that it uses AND operators, not OR. This leads to the following problem:
Some people (not necessarily many but often key customers) will search for john+doe+jane and find nothing. Had they searched for just john+doe they'd have found a ton of results. Or maybe they simply misspell a word or, worse, it was misspeled in the article etc. I need this fixed somehow.
I tried all the plugins, but they either fare worse than the default search or they just won't work (likely because I also made other customizations to the search, but I can't go back on those). So eventually I tried to work my own way out.
I know next to nothing about databases (and not much about Wordpress hooks either), so I tried to move the OR issue to php.
My thinking: First of all, are there quite a few search results? If true, trust Wordpress search that it has done its job for 99+ percent of cases. But are there very few or none at all? Then there may be a problem. Step in, try and fix it!
So, for when there are fewer than 10 results, I made this fallback script:
The solution:
// [Wordpress search loop ran before this]
// find out how many results below the target
$missing = 10 - count($posts);
// or `$missing = 10 - $wp_query->found_posts` - all the same – but already constructed this `$posts` array which I'll need later anyway.
// only do it if you actually need it (less than 10 search results from WP)
if ($missing > 0) {
// give each search term its own life
$terms = explode(" ",$string);
// where `$string = get_query_var('s')` // or `$string = explode("+",$_SERVER['REQUEST_URI'])` in a more generic environment.
// ...
$weight = array();
$results = array();
// start some nasty nested foreaches to search for each term
foreach ($terms as $term) {
// first, get this huge array of posts // wordpress stuff
$results = get_posts(array('s' => $term,'numberposts' => 10));
// then iterate through each of them
foreach ($results as $result) {
// (drop mostly useless one-or-two-letter words)
if (strlen($term) < 3) continue;
// reward each occurence with a biscuit, they'll prove useful later*
$matches[$result->ID] += 1;
// don't let any term become a neverending story (stop inner foreach)
if(count($matches) == 10) break;
}
// stop the game altogether – by now we should have just enough (stop outer foreach)
if(count($matches) > 100) break;
}
// sort the results nicely by biscuits awarded
// *(so if one term came up 3/4 times it goes before one that one that came up 2/4)
arsort($matches);
// to make arrays compatible it's ok to forget the exact biscuit numbers (they don't really matter anymore)
$matches = array_keys($matches);
// if Wordpress found you first we don't need you, you're already up there in the original loop
$fallbacks = array_diff($matches,$posts);
// [standard wordpress loop]
$fallback = new WP_Query( array (
'post__in' => $fallbacks,
'orderby' => post__in,
// add just enough to get to ten
'posts_per_page' => $missing
)
);
if ( $fallback->have_posts() ) {
while ( $fallback->have_posts() ) {
$fallback->the_post();
// [magic goes here]
}
}
}
Does the job. However...
The issues I'm aware of:
Performance: It takes long but not too long. Page (openresty/nginx+redis+varnish) would load in .8s instead of the usual .3 cached or .4-.5 busted*.
Bad bots doing bad stuff: There's merciless sanitizing in WP and there's decent rate-limiting on the webserver, throwing nice 400's and 429's**.
The issues I'm not aware of:
*Not live yet so I don't now how it would scale. Too many at once – what could happen? Can that sort of nested foreach kill a database?
**I'd hate if someone still manages to find a weak spot before I do. Any in sight?