Malicious-like query bring my WP site down

I have this query that is bringing my website to it’s knees. I started seeing it yesterday. I have no idea where it originates from. I definitely do not have that sort of a query in my theme. I use a few plugins as I prefer to write my own. At first I thought we were been injected in the search box, I hard search.php. The query kept popping. Then I disable SEO sitemaps. The query kept popping. Now I don’t know where to look. Have we been compromised in some way? What is going on?

Does anyone have an idea where this sort of query could be originating from?

`SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND (((wp_posts.post_title LIKE ‘%community%’) OR (wp_posts.post_content LIKE ‘%community%’)) AND ((wp_posts.post_title LIKE ‘%development%’) OR (wp_posts.post_content LIKE ‘%development%’))) AND (wp_posts.post_password = ”) AND wp_posts.post_type IN (‘post’, ‘page’, ‘attachment’, ‘afp_feed_article’, ‘byline_bio_box’, ‘network_news’, ‘weather’, ‘event’, ‘tweet_of_the_day’, ‘video_of_the_day’, ‘cxt_site_poll’, ‘cxt_daily_cartoon’, ‘citizen_gallery’, ‘phakaaathi_log’, ‘phakaaathi_video’, ‘phakaaathi_gallery’, ‘phakaathi_mmedia’, ‘multimedia’, ‘fixtures_results’) AND (wp_posts.post_status = ‘publish’) ORDER BY (CASE WHEN wp_posts.post_title LIKE ‘%community development %’ THEN 1 WHEN wp_posts.post_title LIKE ‘%community%’ AND wp_posts.post_title LIKE ‘%development%’ THEN 2 WHEN wp_posts.post_title LIKE ‘%community%’ OR wp_posts.post_title LIKE ‘%development%’ THEN 3 WHEN wp_posts.post_content LIKE ‘%community development %’ THEN 4 ELSE 5 END), wp_posts.post_date DESC LIMIT 0, 10;’

‘afp_feed_article’, ‘byline_bio_box’, ‘network_news’, ‘weather’, ‘event’, ‘tweet_of_the_day’, ‘video_of_the_day’, ‘cxt_site_poll’, ‘cxt_daily_cartoon’, ‘citizen_gallery’, ‘phakaaathi_log’, ‘phakaaathi_video’, ‘phakaaathi_gallery’, ‘phakaathi_mmedia’, ‘multimedia’, ‘fixtures_results’ are my custom post types.

The words/phrases been searched for in the query keep changing. It will be “community”, then a celebrity nae, then a football club, etc.
Once this query is executed about 5 times, the query below pops up and subsequently all the queries on the site become slow and the database stops responding.

SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page', 'attachment', 'afp_feed_article', 'byline_bio_box', 'network_news', 'weather', 'event', 'tweet_of_the_day', 'video_of_the_day', 'cxt_site_poll', 'cxt_daily_cartoon', 'citizen_gallery', 'phakaaathi_log', 'phakaaathi_video', 'phakaaathi_gallery', 'phakaathi_mmedia', 'multimedia', 'fixtures_results') ORDER BY post_modified_gmt DESC LIMIT 1;