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Mysql 5.7 Fulltext search sometimes very slow
Posted by: lisheng1 zhang1
Date: March 21, 2017 02:07PM

we have been using mySQL fulltext search for sometime and recently upgraded from 5.5 to 5.7 (using innoDB fulltext search now), it works well feature wise, thanks a lot!

we noticed each morning the 1st fulltext search is usually rather slow (50s), if we repeat same SQL (even with SQL_NO_CACHE) it would be much faster (1-2s), we really need to overcome the initial slowness, your guidance would be really appreciated.

Main Table (which has about 1.2M records):
CREATE TABLE `OBJECT_SEARCH` (
`ID` bigint(20) unsigned NOT NULL,
`DATA` longtext,
`TITLE_DATA` longtext,
`APPEN_DATA` longtext,
PRIMARY KEY (`ID`),
FULLTEXT KEY `SEARCH_IDX` (`DATA`),
FULLTEXT KEY `SEARCH_TITLE_IDX` (`TITLE_DATA`),
FULLTEXT KEY `SEARCH_APPEN_IDX` (`APPEN_DATA`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

FT variables (for our app we need to index all common words):
innodb_ft_aux_table | |
innodb_ft_cache_size | 8000000 |
innodb_ft_enable_diag_print | OFF |
innodb_ft_enable_stopword | OFF |
innodb_ft_max_token_size | 84 |
innodb_ft_min_token_size | 1 |
innodb_ft_num_word_optimize | 2000 |
innodb_ft_result_cache_limit | 2000000000 |
innodb_ft_server_stopword_table | |
innodb_ft_sort_pll_degree | 2 |
innodb_ft_total_cache_size | 640000000 |
innodb_ft_user_stopword_table | |


SQL (we need to join a few tables to limit the search scope, without those constraints SQL would be much slower):
SELECT DISTINCT b.ID,b.ACTIVITY_TIME FROM OBJECT_SEARCH AS c straight_join CV_13760_OBJECT_DATA AS b on ((b.ID) = (c.ID)) inner join CV_13760_OBJECTS AS a on ((b.ID) = (a.ID)) WHERE (((((((((((((((((((((((((b.TYPE) = '27') OR (((b.TYPE) = '29') AND ((b.SUBTYPE) IN ('20')))) OR (((b.TYPE) = '20') AND ((b.SUBTYPE) NOT IN ('23')))) OR (((b.TYPE) = '16') AND ((b.SUBTYPE) IN ('18')))) OR ((b.TYPE) = '2')) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('5')))) OR (((b.TYPE) = '16') AND ((b.SUBTYPE) IN ('18')))) OR (((b.TYPE) = '16') AND ((b.SUBTYPE) IN ('18')))) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('1')))) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('0')))) OR ((b.TYPE) = '38')) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('7')))) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('3')))) OR ((b.TYPE) = '22')) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('7')))) OR ((b.TYPE) = '4')) OR ((b.TYPE) = '4')) OR (((b.TYPE) = '22') AND ((b.SUBTYPE) IN ('0')))) OR (((b.TYPE) = '2') AND ((b.SUBTYPE) IN ('7')))) OR (((b.TYPE) = '22') AND ((b.SUBTYPE) IN ('1')))) OR (((b.TYPE) = '20') AND ((b.SUBTYPE) IN ('23')))) OR (((b.TYPE) = '11') AND (((b.LIFECYCLE_STATE) = '1') OR ((b.LIFECYCLE_STATE) = '0')))) OR (((b.TYPE) = '11') AND (((b.LIFECYCLE_STATE) = '1') OR ((b.LIFECYCLE_STATE) = '0')))) OR (((b.TYPE) = '20') AND ((b.SUBTYPE) IN ('23')))) AND ((match(c.TITLE_DATA) against(' ( +vmoso)' in Boolean Mode) OR match(c.DATA) against(' ( +vmoso)' in Boolean Mode)) OR match(c.APPEN_DATA) against(' ( +vmoso)' in Boolean Mode)) AND ((b.STATUS) IN ('1')) ORDER BY (b.ACTIVITY_TIME) DESC , (b.ID) DESC LIMIT 0,11;

Query plan:
+----+-------------+-------+------------+--------+--------------------------------------------------+---------+---------+---------------+-------+----------+----------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+--------+--------------------------------------------------+---------+---------+---------------+-------+----------+----------------------------------------------+
| 1 | SIMPLE | a | NULL | index | PRIMARY | PRIMARY | 8 | NULL | 39391 | 100.00 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | c | NULL | eq_ref | PRIMARY | PRIMARY | 8 | vmoso_db.a.ID | 1 | 29.76 | Using where |
| 1 | SIMPLE | b | NULL | eq_ref | PRIMARY,OBJECT_TYPE_INDEX,OBJECT_LIFECYCLE_INDEX | PRIMARY | 8 | vmoso_db.a.ID | 1 | 9.05 | Using where |
+----+-------------+-------+------------+--------+--------------------------------------------------+---------+---------+---------------+-------+----------+----------------------------------------------+

In query plan i did not fulltext index is mentioned (without using fulltext index how could above SQL get executed?)

Thanks very much for helps

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Mysql 5.7 Fulltext search sometimes very slow
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