Sample random revisions from big namespaces

SQL

# http://jan.kneschke.de/projects/mysql/order-by-rand/
# https://stackoverflow.com/questions/249301/simple-random-samples-from-a-sql-database
 
### All non-deleted revisions in the article namespace
#SELECT revision.rev_id, page.* FROM revision
#JOIN page on revision.rev_page = page.page_id
#JOIN (SELECT CEIL(RAND() * (SELECT MAX(rev_id) FROM revision)) AS rev_id) AS random
#WHERE revision.rev_id = random.rev_id
#AND rev_deleted = 0 AND page_namespace = 0;
DELIMITER $$
DROP PROCEDURE IF EXISTS get_rands$$
CREATE PROCEDURE get_rands (IN cnt INT)
BEGIN
  DROP TEMPORARY TABLE IF EXISTS rands;
  CREATE TEMPORARY TABLE rands ( rand_id INT );

loop_me: LOOP
    IF cnt < 1 THEN
      LEAVE loop_me;
    END IF;

    INSERT INTO rands
       	SELECT revision.rev_id, page.* FROM revision
		JOIN page on revision.rev_page = page.page_id
		JOIN (SELECT CEIL(RAND() * (SELECT MAX(rev_id) FROM revision)) AS rev_id) AS random
		WHERE revision.rev_id = random.rev_id
		AND rev_deleted = 0 AND page_namespace = 0;
    SET cnt = cnt - 1;
  END LOOP loop_me;
END$$
DELIMITER ;

CALL get_rands(4);
SELECT * FROM rands;
### All non-deleted revisions in the article-talk namespace
#SELECT * FROM revision JOIN page on revision.page_id = page.page_id WHERE rev_deleted = 0 AND page_namespace = 1 ORDER BY RAND() LIMIT 10000;

### All non-deleted revisions in the user namespace
#SELECT * FROM revision JOIN page on revision.page_id = page.page_id WHERE rev_deleted = 0 AND page_namespace = 2 ORDER BY RAND() LIMIT 10000;

### All non-deleted revisions in the user-talk namespace
#SELECT * FROM revision JOIN page on revision.page_id = page.page_id WHERE rev_deleted = 0 AND page_namespace = 3 ORDER BY RAND() LIMIT 10000;
SQL

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