The right indexes for query

Question

I have this query that's taking 1.7 seconds to perform:

SELECT
    i.id_items AS id, 
    i.names, 
    GROUP_CONCAT(DISTINCT iafv.face_value ORDER BY iafv.face_value ASC SEPARATOR ', ') AS facesValues, 
    GROUP_CONCAT(DISTINCT iacut.translation ORDER BY iacut.translation ASC SEPARATOR ', ') AS currencies, 
    GROUP_CONCAT(DISTINCT cout.translation ORDER BY cout.translation ASC SEPARATOR ', ') AS countries, 
    GROUP_CONCAT(DISTINCT iacot.translation ORDER BY iacot.translation ASC SEPARATOR ', ') AS compositions, 
    GROUP_CONCAT(DISTINCT iacc.catalog_code ORDER BY iacc.catalog_code ASC SEPARATOR ', ') AS catalogCodes, 
    GROUP_CONCAT(DISTINCT iaio.issues_on ORDER BY iaio.issues_on ASC SEPARATOR ', ') AS issuesOn, 
    GROUP_CONCAT(DISTINCT iali.last_issues ORDER BY iali.last_issues ASC SEPARATOR ', ') AS latestIssues, 
    MIN(ucfs.price) AS minPrice, 
    SUM(ucfs.units) AS totalUnits           
FROM
    (SELECT
        i.id_items, 
        GROUP_CONCAT(DISTINCT iant.translation ORDER BY iant.translation asc SEPARATOR ', ') AS names   
    FROM
       items i 
    INNER JOIN languages AS l ON l.language_code = "en"
    LEFT JOIN items_atr_names_match AS ianm ON ianm.id_items = i.id_items
    LEFT JOIN items_atr_names_translations AS iant ON iant.id_items_atr_names = ianm.id_items_atr_names AND iant.id_language_code = l.id_languages 
    LEFT JOIN items_atr_names AS ian ON ian.id_items_atr_names = ianm.id_items_atr_names 

    GROUP BY id_items
    ORDER BY names asc

    LIMIT 0, 20) AS i

INNER JOIN languages AS l ON l.language_code = "en"

LEFT JOIN items_atr_faces_values_match AS iafvm ON iafvm.id_items = i.id_items 
LEFT JOIN items_atr_faces_values AS iafv ON iafv.id_items_atr_faces_values = iafvm.id_items_atr_faces_values

LEFT JOIN items_atr_currencies_match AS iacum ON iacum.id_items = i.id_items 
LEFT JOIN items_atr_currencies_translations AS iacut ON iacut.id_items_atr_currencies = iacum.id_items_atr_currencies AND iacut.id_language_code = l.id_languages 
LEFT JOIN items_atr_currencies AS iacu ON iacu.id_items_atr_currencies = iacum.id_items_atr_currencies

LEFT JOIN items_atr_countries_match AS iacoum ON iacoum.id_items = i.id_items 
LEFT JOIN items_atr_countries_translations AS cout ON cout.id_items_atr_countries = iacoum.id_items_atr_countries AND cout.id_language_code = l.id_languages 
LEFT JOIN items_atr_countries AS cou ON cou.id_items_atr_countries = iacoum.id_items_atr_countries

LEFT JOIN items_atr_compositions_match AS iacom ON iacom.id_items = i.id_items 
LEFT JOIN items_atr_compositions_translations AS iacot ON iacot.id_items_atr_compositions = iacom.id_items_atr_compositions AND iacot.id_language_code = l.id_languages 
LEFT JOIN items_atr_compositions AS iaco ON iaco.id_items_atr_compositions = iacom.id_items_atr_compositions

LEFT JOIN items_atr_catalog_codes_match AS iaccm ON iaccm.id_items = i.id_items
LEFT JOIN items_atr_catalog_codes AS iacc ON iacc.id_items_atr_catalog_codes = iaccm.id_items_atr_catalog_codes  

LEFT JOIN items_atr_issues_on_match AS iaiom ON iaiom.id_items = i.id_items
LEFT JOIN items_atr_issues_on AS iaio ON iaio.id_items_atr_issues_on = iaiom.id_items_atr_issues_on

LEFT JOIN items_atr_last_issues_match AS ialim ON ialim.id_items = i.id_items
LEFT JOIN items_atr_last_issues AS iali ON iali.id_items_atr_last_issues = ialim.id_items_atr_last_issues

LEFT JOIN users_coins_for_sale AS ucfs ON ucfs.id_items = i.id_items
LEFT JOIN users AS u ON u.id_users = ucfs.id_users AND u.status = 'active'

GROUP BY id

ORDER BY names asc

This is creation sql for the tables with the index information:

CREATE TABLE IF NOT EXISTS `items` (
    `id_items` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_users` int(11) unsigned NOT NULL DEFAULT '0',
    `date` date NOT NULL,
    `views` bigint(20) NOT NULL DEFAULT '0',
    `status` enum('draft','published') NOT NULL DEFAULT 'draft',
    PRIMARY KEY (`id_items`),
    UNIQUE KEY `id_items` (`id_items`),
    KEY `id_users` (`id_users`),
    CONSTRAINT `FK_items_users` FOREIGN KEY (`id_users`) REFERENCES `users` (`id_users`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_catalog_codes` (
    `id_items_atr_catalog_codes` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `catalog_code` varchar(100) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_catalog_codes`),
    UNIQUE KEY `id_items_atr_catalog_codes` (`id_items_atr_catalog_codes`),
    FULLTEXT KEY `catalog_code` (`catalog_code`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_catalog_codes_match` (
    `id_items_atr_catalog_codes_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_catalog_codes` int(11) unsigned NOT NULL,
    `id_items` int(11) unsigned NOT NULL,
    PRIMARY KEY (`id_items_atr_catalog_codes_match`),
    UNIQUE KEY `id_items_atr_catalog_codes_match` (`id_items_atr_catalog_codes_match`),
    KEY `id_items` (`id_items`),
    KEY `id_items_atr_catalog_codes` (`id_items_atr_catalog_codes`),
    CONSTRAINT `FK_catalog_codes_items_match_catalog_codes` FOREIGN KEY (`id_items_atr_catalog_codes`) REFERENCES `items_atr_catalog_codes` (`id_items_atr_catalog_codes`),
    CONSTRAINT `FK_catalog_codes_items_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_compositions` (
    `id_items_atr_compositions` int(11) unsigned NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (`id_items_atr_compositions`),
    UNIQUE KEY `id_items_atr_compositions` (`id_items_atr_compositions`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_compositions_match` (
    `id_items_atr_compositions_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_compositions` int(11) unsigned NOT NULL DEFAULT '0',
    `id_items` int(11) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_compositions_match`),
    UNIQUE KEY `id_items_atr_compositions_match` (`id_items_atr_compositions_match`),
    KEY `id_items` (`id_items`),
    KEY `id_items_atr_compositions` (`id_items_atr_compositions`),
    CONSTRAINT `FK_compositions_items_match_compositions` FOREIGN KEY (`id_items_atr_compositions`) REFERENCES `items_atr_compositions` (`id_items_atr_compositions`),
    CONSTRAINT `FK_compositions_items_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_compositions_translations` (
    `id_items_atr_compositions_translations` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_compositions` int(11) unsigned NOT NULL DEFAULT '0',
    `id_language_code` int(11) unsigned NOT NULL DEFAULT '0',
    `translation` varchar(250) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_compositions_translations`),
    UNIQUE KEY `id_items_atr_compositions_translations` (`id_items_atr_compositions_translations`),
    KEY `id_language_code` (`id_language_code`),
    KEY `id_items_atr_compositions` (`id_items_atr_compositions`),
    FULLTEXT KEY `translation` (`translation`),
    CONSTRAINT `FK_compositions_translations_compositions` FOREIGN KEY (`id_items_atr_compositions`) REFERENCES `items_atr_compositions` (`id_items_atr_compositions`),
    CONSTRAINT `FK_compositions_translations_languages` FOREIGN KEY (`id_language_code`) REFERENCES `languages` (`id_languages`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_countries` (
    `id_items_atr_countries` int(11) unsigned NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (`id_items_atr_countries`),
    UNIQUE KEY `id_items_atr_countries` (`id_items_atr_countries`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `items_atr_countries_match` (
    `id_items_atr_countries_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_countries` int(11) unsigned NOT NULL,
    `id_items` int(11) unsigned NOT NULL,
    PRIMARY KEY (`id_items_atr_countries_match`),
    UNIQUE KEY `items_atr_countries_match` (`id_items_atr_countries_match`),
    KEY `id_items` (`id_items`),
    KEY `id_items_atr_countries` (`id_items_atr_countries`),
    CONSTRAINT `FK__countries` FOREIGN KEY (`id_items_atr_countries`) REFERENCES `items_atr_countries` (`id_items_atr_countries`),
    CONSTRAINT `FK__items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_countries_translations` (
    `id_items_atr_countries_translations` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_countries` int(11) unsigned NOT NULL DEFAULT '0',
    `id_language_code` int(11) unsigned NOT NULL DEFAULT '0',
    `translation` varchar(250) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_countries_translations`),
    UNIQUE KEY `id_items_atr_countries_translations` (`id_items_atr_countries_translations`),
    KEY `id_items_atr_countries` (`id_items_atr_countries`),
    KEY `id_language_code` (`id_language_code`),
    FULLTEXT KEY `translation` (`translation`),
    CONSTRAINT `FK__items_atr_countries` FOREIGN KEY (`id_items_atr_countries`) REFERENCES `items_atr_countries` (`id_items_atr_countries`),
    CONSTRAINT `FK_items_atr_countries_translations_languages` FOREIGN KEY (`id_language_code`) REFERENCES `languages` (`id_languages`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_currencies` (
    `id_items_atr_currencies` int(11) unsigned NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (`id_items_atr_currencies`),
    UNIQUE KEY `id_items_atr_currencies` (`id_items_atr_currencies`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_currencies_match` (
    `id_items_atr_currencies_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_currencies` int(11) unsigned NOT NULL DEFAULT '0',
    `id_items` int(11) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_currencies_match`),
    UNIQUE KEY `id_items_atr_currencies_match` (`id_items_atr_currencies_match`),
    KEY `id_items_atr_currencies` (`id_items_atr_currencies`),
    KEY `id_items` (`id_items`),
    CONSTRAINT `FK_items_atr_currencies_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`),
    CONSTRAINT `FK_items_atr_currencies_match_items_atr_currencies` FOREIGN KEY (`id_items_atr_currencies`) REFERENCES `items_atr_currencies` (`id_items_atr_currencies`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_currencies_translations` (
    `id_items_atr_currencies_translations` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_currencies` int(11) unsigned NOT NULL DEFAULT '0',
    `id_language_code` int(11) unsigned NOT NULL DEFAULT '0',
    `translation` varchar(255) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_currencies_translations`),
    UNIQUE KEY `id_items_atr_currencies_translations` (`id_items_atr_currencies_translations`),
    KEY `id_items_atr_currencies` (`id_items_atr_currencies`),
    KEY `id_language_code` (`id_language_code`),
    FULLTEXT KEY `translation` (`translation`),
    CONSTRAINT `FK_items_atr_currencies_translations_items_atr_currencies` FOREIGN KEY (`id_items_atr_currencies`) REFERENCES `items_atr_currencies` (`id_items_atr_currencies`),
    CONSTRAINT `FK_items_atr_currencies_translations_languages` FOREIGN KEY (`id_language_code`) REFERENCES `languages` (`id_languages`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_faces_values` (
    `id_items_atr_faces_values` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `face_value` decimal(11,2) unsigned NOT NULL DEFAULT '0.00',
    PRIMARY KEY (`id_items_atr_faces_values`),
    KEY `face_value` (`face_value`),
    KEY `id-fv` (`id_items_atr_faces_values`,`face_value`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_faces_values_match` (
    `id_items_atr_faces_values_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_faces_values` int(11) unsigned NOT NULL DEFAULT '0',
    `id_items` int(11) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_faces_values_match`),
    UNIQUE KEY `id_items_atr_faces_values_match` (`id_items_atr_faces_values_match`),
    KEY `id_items_atr_faces_values` (`id_items_atr_faces_values`),
    KEY `id_items` (`id_items`),
    KEY `idItems-IdFaceValue` (`id_items`,`id_items_atr_faces_values`),
    CONSTRAINT `FK_items_atr_faces_values_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`),
    CONSTRAINT `FK_items_atr_faces_values_match_items_atr_faces_values` FOREIGN KEY (`id_items_atr_faces_values`) REFERENCES `items_atr_faces_values` (`id_items_atr_faces_values`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_issues_on` (
    `id_items_atr_issues_on` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `issues_on` varchar(6) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_issues_on`),
    UNIQUE KEY `id_items_atr_issues_on` (`id_items_atr_issues_on`),
    FULLTEXT KEY `issues_on` (`issues_on`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_issues_on_match` (
    `id_items_atr_issues_on_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_issues_on` int(11) unsigned NOT NULL,
    `id_items` int(11) unsigned NOT NULL,
    PRIMARY KEY (`id_items_atr_issues_on_match`),
    UNIQUE KEY `id_items_atr_issues_on_match` (`id_items_atr_issues_on_match`),
    KEY `id_items_atr_issues_on` (`id_items_atr_issues_on`),
    KEY `id_items` (`id_items`),
    CONSTRAINT `FK_items_atr_issues_on_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`),
    CONSTRAINT `FK_items_atr_issues_on_match_items_atr_issues_on` FOREIGN KEY (`id_items_atr_issues_on`) REFERENCES `items_atr_issues_on` (`id_items_atr_issues_on`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_last_issues` (
    `id_items_atr_last_issues` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `last_issues` varchar(6) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_last_issues`),
    UNIQUE KEY `id_items_atr_last_issues` (`id_items_atr_last_issues`),
    FULLTEXT KEY `last_issues` (`last_issues`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_last_issues_match` (
    `id_items_atr_last_issues_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_last_issues` int(11) unsigned NOT NULL DEFAULT '0',
    `id_items` int(11) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_last_issues_match`),
    UNIQUE KEY `id_items_atr_last_issues_match` (`id_items_atr_last_issues_match`),
    KEY `id_items_atr_last_issues` (`id_items_atr_last_issues`),
    KEY `id_items` (`id_items`),
    CONSTRAINT `FK_items_atr_last_issues_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`),
    CONSTRAINT `FK_items_atr_last_issues_match_items_atr_last_issues` FOREIGN KEY (`id_items_atr_last_issues`) REFERENCES `items_atr_last_issues` (`id_items_atr_last_issues`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_names` (
    `id_items_atr_names` int(11) unsigned NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (`id_items_atr_names`),
    UNIQUE KEY `id_items_atr_names` (`id_items_atr_names`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_names_match` (
    `id_items_atr_names_match` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_names` int(11) unsigned NOT NULL DEFAULT '0',
    `id_items` int(11) unsigned NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_names_match`),
    UNIQUE KEY `id_items_atr_names_match` (`id_items_atr_names_match`),
    KEY `id_items_atr_names` (`id_items_atr_names`),
    KEY `id_items` (`id_items`),
    CONSTRAINT `FK_items_atr_names_match_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`),
    CONSTRAINT `FK_items_atr_names_match_items_atr_names` FOREIGN KEY (`id_items_atr_names`) REFERENCES `items_atr_names` (`id_items_atr_names`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `items_atr_names_translations` (
    `id_items_atr_names_translations` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items_atr_names` int(11) unsigned NOT NULL DEFAULT '0',
    `id_language_code` int(11) unsigned NOT NULL DEFAULT '0',
    `translation` varchar(250) NOT NULL DEFAULT '0',
    PRIMARY KEY (`id_items_atr_names_translations`),
    UNIQUE KEY `id_items_atr_names_translations` (`id_items_atr_names_translations`),
    KEY `id_language_code` (`id_language_code`),
    KEY `id_items_atr_names` (`id_items_atr_names`),
    KEY `translation_indx` (`translation`),
    FULLTEXT KEY `translation` (`translation`),
    CONSTRAINT `FK_items_atr_names_translations_items_atr_names` FOREIGN KEY (`id_items_atr_names`) REFERENCES `items_atr_names` (`id_items_atr_names`),
    CONSTRAINT `FK_items_atr_names_translations_languages` FOREIGN KEY (`id_language_code`) REFERENCES `languages` (`id_languages`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `languages` (
    `id_languages` int(11) unsigned NOT NULL,
    `language_code` char(2) NOT NULL,
    PRIMARY KEY (`id_languages`),
    UNIQUE KEY `language_code` (`language_code`),
    KEY `id-language_code` (`id_languages`,`language_code`),
    KEY `language-code` (`language_code`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `languages_translations` (
    `id_languages_translations` int(11) unsigned NOT NULL,
    `id_languages` int(11) unsigned NOT NULL,
    `id_language_code` int(11) unsigned NOT NULL,
    `translation` varchar(255) NOT NULL,
    PRIMARY KEY (`id_languages_translations`),
    UNIQUE KEY `id_languages_translations` (`id_languages_translations`),
    KEY `id_languages` (`id_languages`),
    KEY `language_code` (`id_language_code`),
    FULLTEXT KEY `translation` (`translation`),
    CONSTRAINT `FK_languages_translations_languages` FOREIGN KEY (`id_languages`) REFERENCES `languages` (`id_languages`),
    CONSTRAINT `FK_languages_translations_languages_2` FOREIGN KEY (`id_language_code`) REFERENCES `languages` (`id_languages`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `users_coins_for_sale` (
    `id_users_coins_for_sale` int(11) unsigned NOT NULL AUTO_INCREMENT,
    `id_items` int(11) unsigned NOT NULL,
    `id_users` int(11) unsigned NOT NULL,
    `units` int(5) unsigned NOT NULL,
    `year` varchar(5) NOT NULL,
    `grade` enum('good','very_good','fine','very_fine','extra_fine','about_uncirculated','uncirculated','brilliant_uncirculated','proof') NOT NULL,
    `price` decimal(8,2) unsigned NOT NULL,
    `picture` varchar(500) DEFAULT NULL,
    `comment` varchar(500) DEFAULT NULL,
    `date` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    PRIMARY KEY (`id_users_coins_for_sale`),
    UNIQUE KEY `id_users_coins_for_sale_unique` (`id_users_coins_for_sale`),
    KEY `id_items` (`id_items`),
    KEY `id_users` (`id_users`),
    KEY `year` (`year`),
    KEY `grade` (`grade`),
    KEY `id_users_coins_for_sale` (`id_users_coins_for_sale`),
    KEY `idItems-idUsers` (`id_items`,`id_users`),
    CONSTRAINT `FK_users_coins_for_sale_items` FOREIGN KEY (`id_items`) REFERENCES `items` (`id_items`),
    CONSTRAINT `FK_users_coins_for_sale_users` FOREIGN KEY (`id_users`) REFERENCES `users` (`id_users`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Here is the explain of the query:

In the explain I can see sometimes the indexes are used but sometimes not, I wonder what I can do to improve the performance in this query, if I've created the index correctly or if I'm missing any index.

The items table has 90k entries but I think it's not big enough to take 1.7 seconds...

I've been following this link to learn best practices: https://stackoverflow.com/a/3049329

Do you have any advice about how I can improve the performance?

Thanks in advance

1.7 seconds seems all right to me. Best practice is surely to not use GROUP_CONCAT, and instead handle issues of data display in application code — Strawberry, Jun 12 '17 at 21:52
Thanks @Strawberry, so is it normal that in the 'Extra' column in the query explanation appear null values? It takes about the same (1.4 secs) if I remove the GROUP_CONCAT from the select. The bottle neck must be in other part I can't see — Nicolás González, Jun 12 '17 at 22:05
What happens to the result if you remove `users`, `items_atr_compositions`, `items_atr_compositions_translations`, and `items_atr_countries` from the query? — Strawberry, Jun 12 '17 at 22:27
If I take out the ones you say, it takes from 1.359 sec to 1.484 sec to execute — Nicolás González, Jun 12 '17 at 22:33

score 0 · Answer 1 · answered Jun 28 '17 at 06:21

If the JOINs are not 1:1, the SUM() may be inflated. Check the value!
When the GROUP BY and ORDER BY are different, no index will help avoid gathering the tentative resultset before the LIMIT. Otherwise, some index might reach all the way to the LIMIT, thereby avoiding a full scan.
A PRIMARY KEY is a UNIQUE KEY, so the latter is redundant; DROP it. (I see that patter in in all(?) the tables.)
This discusses optimal indexes for many:many mapping tables.
This smells like a "key-value" or "EAV" schema, which sucks.
Sometimes it is better change

this

GROUP_CONCAT(DISTINCT ... )
...
LEFT JOIN ...

into

( SELECT GROUP_CONCAT( ... ) FROM ... )

The above suggestion is especially important in the derived query, since it is probably the slowest part. Recommend you pull out that subquery and time it and work on optimizing it. Note that it may scan lots of rows, but deliver no more than 20. Then those 20 should not be too much burden on the rest of the queries, assuming you have at least the minimal indexes.
Alas, that is only half useful -- It may get rid of the GROUP BY, but it cannot get rid of the full scan. This is because the ORDER BY depends on a computed value (names). Still, it should get rid of the "inflate-deflate" caused by JOINs + GROUP BY.
Get rid of the table languages. All it does is map a 2-byte language_like like 'en' to a 4-byte INT. This is a waste of (1) space, and (2) JOINs.

Sorry, but this list of suggestions is probably incomplete. Please do what you can to improve things, then come back for more help.

The right indexes for query

1 Answers1