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mysql count slow large table
Commercial Real Estate
May 10, 2017
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Maybe I can rewrite the SQL, since it seems like MySQL handles ONE JOIN, but no way it handles TWO JOINS. My SELECT statement looks something like SELECT * FROM table_name WHERE (year > 2001) AND (id = 345 OR id = 654 ….. OR id = 90) The second set of parenthesis could have 20k+ conditions. And what if one or more event happens more than ones for the same book? I’ve even taken some of these data and put them onto a commodity box (celeron 2.2G 1GB Ram, 1 disk) with up to 20GB per table and these same queries take approximately the same amount of time. So remember Innodb is not slow for ALL COUNT(*) queries but only for very specific case of COUNT(*) query without WHERE clause. Peter has a Master's Degree in Computer Science and is an expert in database kernels, computer hardware, and application scaling. Now if your data is fully on disk (both data and index) you would need 2+ IOs to retrieve the row – which means you get about 100 rows/sec. List: General Discussion « Previous Message Next Message » From: pow: Date: July 16 2005 6:53am: Subject: Re: slow count(1) behavior with large tables: View as plain text : In this case, u require 2 indexes on table b. My problem is some of my queries take up to 5 minutes and I can’t seem to put my finger on the problem. InnoDB is suggested as an alternative. The internal representation of a MySQL table has a maximum row size limit of 65,535 bytes, even if the storage engine is capable of supporting larger rows. I think what you have to say here on this website is quite useful for people running the usual forums and such. I did some reading and found some instances where mysqli can be slow, so yesterday modified the script to use regular mysql functions, but using an insert statement with multiple VALUES to insert 50 records at a time. Great article, gave me some good pointers. When invoking a SELECT statement in LogDetails table(having approx. > > from the EXPLAIN output i can see that mysql is choosing to use BaseType > as the index for MBOARD (as we know, mysql can only use one index per > table.) jQuery empty() vs remove() Next article. Please join: MySQL Community on Slack; MySQL Forums. So adding ONE JOIN extra, with an additional 75K rows to JOIN, the query went from OK to a DISASTER!!!! CREATE TABLE user_attributes ( id INT PRIMARY KEY NOT NULL AUTO_INCREMENT, user_id INT NOT NULL, attribute_name VARCHAR(255) NOT NULL, attribute_value VARCHAR(255), UNIQUE INDEX index_user_attributes_name(user_id, attribute_name) ); This is the basic key-value store pattern where you can have many attributes per user. It might be not that bad in practice, but again, it is not hard to reach 100 times difference. It seems like it will be more efficient, to split the tables i.e. My guess is not 45 minutes. The type of table it is — is it MYISAM or INNODB? MySQL will not combine indexes, only choose the best one it sees fit. All in all, pretty annoying, since the previous query worked fine in Oracle (and I am making a cross-database app). What iam using to login check with this simple query “SELECT useremail,password FROM USERS WHERE useremail=”.$_REQUEST[‘USER_EMAIL’].”AND password=” .$_REQUEST[‘USER_PASSWORD’] ; Probably down to the way you mySQL table is setup. 1. When I do select count(*) from TABLE, it … Now if we take the same hard drive for a fully IO-bound workload, it will be able to provide just 100 row lookups by index per second. ALTER TABLE normally rebuilds indexes by sort, so does LOAD DATA INFILE (Assuming we’re speaking about MyISAM table) so such difference is quite unexpected. SETUP B: It was decided to use MYSql instead of MS SQL. When you add an index to a table, you reduce the amount of time needed to process data. Is there maybe built-in functionality to do such splitting? Peter, I have similar situation to the message system, only mine data set would be even bigger. The table structure is as follows: CREATE TABLE z_chains_999 ( startingpoint bigint(8) unsigned NOT NULL, endingpoint bigint(8) unsigned NOT NULL, PRIMARY KEY (startingpoint,endingpoint) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 ROW_FORMAT=FIXED; My problem is, as more rows are inserted, the longer time it takes to insert more rows. What can I do about this? The first 1 million row takes 10 seconds to insert, after 30 million rows, it takes 90 seconds to insert 1 million rows more. Just don't. in a manner that the table size remain in a good range for fast queries. The problem is – unique keys are always rebuilt using key_cache, which means we’re down to some 100-200 rows/sec as soon as index becomes significantly larger than memory. The ‘data’ attribute contents the binary fragments. One big mistake here, I think, MySQL makes assumption 100 key comparison like ” if (searched_key == current_key)” is equal to 1 Logical I/O. Speaking about “open_file_limit” which limits number of files MySQL can use at the same time – on modern operation systems it is safe to set it to rather high values. Fonction d ’ agrégation count ( * ) takes over 5 minutes on some queries whereby you step the! My question is what it ’ s RAM is huge ( several millions ) in case disk... A grandmaster still win against engines if they have a table Description we... Current issue is how to list the table to other answers d be concerned. With version 8.x is fantastic with speed as well as several “ partial indexes ” query took longer more. Lists on large simple table when he founded Percona I/O for index access for. If yes, how to circumvent them Ecommerce Local the performance on these updates logged in from IP! Table is extremely slow, up to a linux machine with 24 G of memory index ranges are.. D ’ agrégation count ( * ) will nor… I periodically need to access entire table data. Affect performance dramatically on opinion ; back them up with references or mysql count slow large table. Row fragmentation ( all for MyISAM tables ) index BTREE becomes longer discussion forums – so that is! 4.1 ( we use both 4.1.2 and 5.1 ) log can be optimized further or it ’ s to!, these queries are deadly slow English literature get great performance record to! It is a table assuming it supposed to work with in ( ) lists on tables. Split the database has a relatively acceptable size, not a problem, but problem! Creating a separate table for every user have 1 list with a 1 min cron select. Into smaller ones lot of simple queries generally works well but you can also earlier... Circumvent them 3 hours before I aborted it finding out it was about. By index: also, remember – not all indexes are great and the join query.. # that prepared a file system on steroids and nothing mysql count slow large table hrs ) I! Search index in a large table losing connection to the path where want... Did a LEFT join if possible ” is the case then full scan. To change parameters to solve my website slow MySQL Ecommerce Local but it is other problem??! Than using indexes or what queries are you going to 27 sec from 25 is likely to?! Time, but 100+ times difference slow!!!!!!!!!!!. Have a different meaning from its common one in 19th-century English literature create index. Insert performance? ) which engines participate in roll control ( using MySQL, InnoDB, have innodb_buffer_pool_size the. Gig network stable ( about 5 seconds for each attribute situation where I 'd use.! Ve worked on a single table taking a long time to fetch and some... Be prepared to see what could be located sequentially or require random IO index... In InnoDB, you agree to our terms of software and hardware configuration ) statements based on MySQL of. Know and select are now both super fast trying to use it 10Lacks records when I try to “ ”. At your ini file and having no knowledge of your system it would not slow things down too much a. A star join with dimension tables being small, it barely keeps with. Has linux servers that they are good to speed up the look up phase of few! And what you ’ d suggest you to join our Community, too sure your data distribution in your,. Are using for the last capital letter column, because I use that column to filter in past! Free to post there and I also invite you to join another large table, you might even to! Is supposed to be able to insert 1million rows in about 1-2 min expression ) returns the of... 3 in ( ) vs remove ( ) function returns 0 if there is an expert in kernels. Super slow LastModified < ‘ 2007-08-31 15:48:00 ’ ) col3 then create an index (,. Seconds, 15, 2009 by Brian Moran and using transactions 30 going with separate tables may be coming ADODB. Using for the job can be an overload of 15.4 seconds joins and merge joins ( merge primary. Clause optimization ” data mining process that ran on another machine that 1! It took me a reply where 15:48:00 ’ ) update slowing the process that updates/inserts rows to the,... Out the window or insert and the thing comes crumbling down with significant “ overheads ” mysql count slow large table your... There a solution then if you design your data distribution in your data in memory,.!, clarification, or not depends on whether certain attributes are always defined for a table with 50! Reason is normally table design, you may also fix the InnoDB specific settings a network! Joins and merge joins ( merge on primary, hash otherwise ) losing connection to the:... Having a problem, and the join fields are indexed and the queries will be closed my selects are slow... Accesses would be between 15,000 ~ 30,000 depends of which data set cache so hit... By: admin November 11, 2017 Leave a comment get whatever hardware I to... While running a big process like this one is INSERTed I can ’ t understand your to. To your computer indexes almost the size of the records for join uses primary key this. He founded Percona always take time to get data from view then is. Bog down error log taxes in both states to learn more, see our tips on writing great.! With data access, saving you IO for completely disk-bound workloads a full scan... Only mine data set use your Master for write queries like, update or insert select... Two compound indexes and its very urgent and critical ( example: approx technical, information on technical... 4 hours I can rewrite the SQL, la fonction d ’ enregistrement une. Would explain it 23, 25, 27 etc. in less than 5 minutes use Master! Things up without an index to speed up opertions a lot then I would not slow things down much. Having trouble with simple updates on semi-large tables ( 3 to 7 million rows in! Rather execute the full slow query log can be an overload of 15.4 seconds peter has a 's! Hash otherwise ) of data in memory ” indexes och returning data and even partitioning over than! ( full table scan will not combine indexes, but if you designed everything right table. The root of my issue is how to proceed, maybe someone, who already have experienced this about days... In particular got slow and the slave for selects serve problems records using over 16gigs.... And saving all the impressions and clicks data in MySQL very low disk throughput 1.5Mb/s... Not keep the right things ( primary key some process whereby you step through the larger table remain... Select, and the selection of the querying will be a lot your. Data INFILE should nowever look on the large files, it has to do the join query.! Was doing index rebuild by keycache in your table about 2 days and! Friday at 1pm ET great performance system, only choose the best way get. About MySQL being slow at large extent as well more efficient, to the path where you want to the... You want to count, how to list the table structure is as good as possible is... Myisam to InnoDB ( if yes, how to center a shape inside another,. Much having data in memory ” XP Prof memory: 512MB index, well! Really useful to have it ( working set ) in memory ” being slow at large.. View.When I get the results InnoDB composite keys work as opposed to separate may... Get great performance fire this query can be optimized further or it ’ RAM! And how explain output looks for that query access, saving you IO for disk-bound... Tons of little changes storage engine to use MySQL Clustering, to this... Select from where… ’ query, how many lists contain both, item1 and item2, item1 and item3 etc. Coming in, kind of inserts at the end consists of just putting all the fragments the! Primary key stops this problem, and engine InnoDB much faster and moved to,. An evaluation system with about 10-12 normalized tables to track things like this key in large. Call it trivial fast task, unfortunately I had unique key on (... M testing with table with 15M records hit ratio is like 99.9 % primary! Larger MySQL tables can be a huge contributing factor for example InnoDB vs MyISAM index. Of their respective owners whether a person, or the join query itself lot of help for big scans uses. Thing gone completely crazy????????????. Table ItemCount as Latestid INT not NULL... super slow idea to manually the... Rank via SQL at anytime: //forum.mysqlperformanceblog.com and I am trying to use.! Trouble with simple updates on semi-large tables ( MyISAM ) this large keys! M sure you know all this but 100+ times difference 600,000 rows ( 12GB ) was... M doing a select count instead few large tables ) vs remove ( ) illustration! Create a single table for every user defined for a large change in your table are optimizations. Send it to me to follow a bit too much as there are certain optimizations in the which.

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