Optimize mysql with inner joins and where - mysql

Question

I have query:
SELECT DISTINCT h.id,
h.host
FROM pozycje p
INNER JOIN hosty h ON p.host_id = h.id
INNER JOIN keywordy k ON k.id=p.key_id
AND k.bing=0
WHERE h.archive_data_checked IS NULL LIMIT 20
It's fast when some rows exists but if no results exists it takes 2,3 sek to execute. I would like to have less than 1 sec. Explain looks like:
http://tinyurl.com/gogx42n
Table pozycje has 30 000 000 rows, hosty has 4 000 000 rows and keywordy has 40 000 rows. Engine InnoDB, server with 32GB RAM
What indexes or improvements can I do to spped up query when no results exists?
edit:
show table keywordy;
CREATE TABLE `keywordy` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`main_kw` varchar(255) CHARACTER SET utf8 NOT NULL,
`keyword` varchar(255) CHARACTER SET utf8 NOT NULL,
`lang` varchar(10) CHARACTER SET utf8 NOT NULL,
`searches` int(11) NOT NULL,
`cpc` float NOT NULL,
`competition` float NOT NULL,
`currency` varchar(10) CHARACTER SET utf8 NOT NULL,
`data` date DEFAULT NULL,
`adwords` int(11) NOT NULL,
`monitoring` tinyint(1) NOT NULL DEFAULT '0',
`bing` tinyint(1) NOT NULL DEFAULT '0',
PRIMARY KEY (`id`),
UNIQUE KEY `keyword` (`keyword`,`lang`),
KEY `id_bing` (`id`,`bing`)
) ENGINE=InnoDB AUTO_INCREMENT=38362 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

Answer 1

can pls test this:
SELECT DISTINCT h.id,
h.host
FROM hosty h
WHERE
EXISTS ( SELECT 1 FROM keywordy WHERE id=p.key_id AND bing=0)
AND
EXISTS ( SELECT 1 FROM pozycje WHERE host_id = h.id)
AND h.archive_data_checked IS NULL LIMIT 20

Answer 2

I would first offer the following question. Which would have the smaller "set" if you did a query on
select count(*) from KeyWordy where bing = 0
vs
select count(*) from hosty where archive_date_checked IS NULL
I would then try to optimize the query knowing the smaller set and work with that as my primary criteria for indexing. If KeyWordy is more likely to be the smaller set, I would offer your tables to have the following indexes
table index
keywordy (bing, id) specifically NOT (id, bing) as bing FIRST is optimized for where or JOIN clause
pozycje (key_id, host_id )
hosty (archive_data_checked, id, host)
SELECT DISTINCT
h.id,
h.host
FROM
Keywordy k
JOIN pozycje p
ON k.id = p.key_id
JOIN hosty h
on archive_data_checked IS NULL
AND p.host_id = h.id
WHERE
k.bing = 0
LIMIT
20
if the HOSTY table would be smaller base on the archive_data_checked IS NULL, I offer the following
table index
pozycje (host_id, key_id ) reversed of other option
SELECT DISTINCT
h.id,
h.host
FROM
hosty h
JOIN pozycje p
ON h.id = p.host_id
JOIN Keywordy k
on k.bing = 0
AND p.key_id = k.id
WHERE
h.archive_data_checked IS NULL
LIMIT
20
One FINAL option, might be to add the keyword "STRAIGHT_JOIN" such as
select STRAIGHT_JOIN DISTINCT ... rest of query
If it works for you, what timing improvements does this offer.