I have 10GB MYISAM table . I’m writing about working with large data sets, these are then your tables and your working set do not fit in memory. The problem was that at about 3pm GMT the SELECTs from this table would take about 7-8 seconds each on a very simple query such as this: SELECT column2, column3 FROM table1 WHERE column1 = id; The index is on column1. For those who is interested it came out like this instead: SELECT COUNT(DISTINCT(u.unit_id)) FROM ( SELECT u1.unit_id FROM unit u1, unit_param up1 WHERE u1.unit_id = up1.unit_id AND up1.unit_type_param_id = 24 AND up1.value = ‘ServiceA’) u2, unit_param up2 WHERE u2.unit_id = up2.unit_id AND up2.unit_type_param_id = 23 AND up2.value = ‘Bigland’. MySQL database really slow with a really big table [closed] Ask Question Asked 6 years, 6 months ago Active 5 years, 11 months ago Viewed 8k times 1 2 Closed. How you obtained a masters degree is beyond me. I have been playing with different indexes and at this time I managed to drop the index’s size to up 1.5GB, which is much more acceptable. The problem I have, is regarding some specific tables in the database, which I use for a couple of months duration, minning them with detailed data of a particular task. On the other hand, it is well known with customers like Google, Yahoo, LiveJournal, and Technorati, MySQL has installations with many billions of rows and delivers great performance. I didn’t said I wanted to combine indexes, I was talking about a combined index. “One of the reasons elevating this problem in MySQL is lack of advanced join methods at this point (the work is on a way) – MySQL can’t do hash join or sort merge join – it only can do nested loops method which requires a lot of index lookups which may be random.”. Why do you have so many short lists? Then run your code and any query above the specified threshold will be added to that file. QUESTION: 1) Why does MS SQL performs faster when they have the same specs though with different OS? A simple AFTER INSERT trigger takes about 7 second. I attempted to use Sphinx to pull the ID’s of all records in a Cat, then lookup the LastModified from MySQL. The things you wrote here are kind of difficult for me to follow. 6 open source tools for staying organized, https://dev.mysql.com/doc/refman/5.7/en/mysqldumpslow.html. The tables are large and when I select a table that is locked to insert. Even storage engines have very important differences which can affect performance dramatically. InnoDB-buffer-pool was set to roughly 52Gigs. (There are only 3 fields of a one characterseach in the table plus one field of 40 characters, which is inexed and is the filed being used for the sql statement relating both tables). You are responsible for ensuring that you have the necessary permission to reuse any work on this site. at least could you able to explain brief in short? 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. Indexes are great and the more the better, but if you want to bulk upload records then you will suffer the consequences. Peter managed the High Performance Group within MySQL until 2006, when he founded Percona. Has the JOIN thing gone completely crazy??? The table structure is as following and it stores uploaded files in many portions (fragments) of max. Sometimes if I have many indexes and need to do bulk inserts or deletes then I will kill the indexes, run my process and then recreate my indexes afterward. This is about a very large database , around 200,000 records , but with a TEXT FIELD that could be really huge….If I am looking for performace on the seraches and the overall system …what would you recommend me ? How on earth could this happen? This query takes ~13 seconds to run (2GHZ Dual Core CPU, 2GB RAM). I use multiple record INSERTs (150 each time), and the first INSERT usually takes 600 secs (when the task starts). If you design your data wisely, considering what MySQL can do and what it can’t, you will get great performance. I've noticed with MySQL that large result queries don't slow down linearly. I suspect that this may make things faster. Let’s do some computations again. Could maybe somebody point me to the most relevant parameters to consider in my case (which parameters, for example, define the amount of memory reserved to handle the index, etc.)? Mysql will be able to use the 2-field > index for both the WHERE and MAX parts of the query and won't have to > touch the table at all. I am stuck! We’ve got 20,000,000 bank loan records we query against all sorts of tables. Ps : reading Eric/k statement, perhaps PostGres could better handle things? I know some big websites are using MySQL, but we had neither the budget to throw all that staff, or time, at it. Consider using FULLTEXT index. So I am wondering, in your experience, is innoDB so efficient that splitting into 30 tables with 1 million records and 300,000 users per table would be noticable. 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. or just If your Access database running slow over network then try this method. Peter, I have similar situation to the message system, only mine data set would be even bigger. I am building a statistics app that will house 9-12 billion rows. Hi. Meanwhile the table has a size of 1,5Gb. At the bottom of this post I've got the mysql.ini config lines, any sugestions are welcome, I'm already beyond the mysql "huge" sample i am using mysql I had a problem with joining table where all table had a records more than 2 lakhs so when I run it from my application. The problem is not the data size; normalized data normally becomes smaller, but a dramatically increased number of index lookups could be random accesses. 2. My problem is some of my queries take up to 5 minutes and I can’t seem to put my finger on the problem. Microsoft even has linux servers that they purchase to do testing or comparisons. (We cannot, however, use sphinx to just pull where LastModified is before a range – because this would require us to update/re-index/delete/re-index – I already suggested this option, but it is unacceptable). So I guess a better question is, 30 million records, 1 million users with 30 records each You mentioned (and I have experienced) that a composite key starting with userid in Innodb is indeed very efficient and fast. It’s of ip traffic logs. Very good article! I did not mentioned it in the article but there is IGNORE INDEX() hint to force full table scan. Just an opinion. Is there something special about a delete that makes it MUCH MUCH slower than a select? MySQL indexes may take up more space and decrease performance on inserts, deletes, and updates. Red Hat and the Red Hat logo are trademarks of Red Hat, Inc., registered in the United States and other countries. CREATE TABLE GRID ( ID bigint(20) NOT NULL auto_increment, STRING varchar(100) character set utf8 collate utf8_unicode_ci NOT NULL default ”, URL varchar(230) character set utf8 collate utf8_unicode_ci NOT NULL default ”, LANGUAGE char(2) NOT NULL default ‘EN’, COUNTRY char(2) NOT NULL, TITLE varchar(255) character set utf8 collate utf8_unicode_ci NOT NULL default ”, DESCRIPTION text character set utf8 collate utf8_unicode_ci, POINTS decimal(10,2) NOT NULL default ‘0.00’, PRIMARY KEY (ID), UNIQUE KEY string (STRING,URL). I was hoping to see the machine either disk or CPU-bound to help troubleshoot what the problem is, but this is not the case. I am using mysql x64 in a PC with 16 GB of RAM on a x64 OS. I suggest instead sharing it on our MySQL discussion forums – so that the entire community can offer some ideas to help. You might even consider to duplicate your data into two (or more) tables, for ex. Mysql will only use one > index for a table per query. 5.0.45 via socket on x86_64 centos 5.2, 1 CPU 4core with 4 Gb RAM, 3Tb SATA disk space Load avg: 0.81 (1 min) 0.68 (5 mins) 0.73 (15 mins) Real memory 3.86 GB total, 1.38 GB used Virtual memory 4 GB total, 288 kB used, I had a problem with COUNT(*) when I run it from my application. On the other hand, I’ll need to select the data even quicker. I don’t know why this happens and if any one also had this problem. What is often forgotten about is,  depending on if the workload is cached or not,  different selectivity might show benefit from using indexes. My website has about 1 million hits daily . I’ve read SHE-DBA’s blog on using MySQL as a data-warehousing platform and where it _can_ be used as such provided the design is good and the queries are optimised. System: It’s now on a 2xDualcore Opteron with 4GB Ram/Debian/Apache2/MySQL4.1/PHP4/SATA Raid1) In near future I will have the Apache on a dedicated machine and the Mysql Server too (and the next step will be a Master/Slave server setup for the database). 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. I do multifield select on indexed fields, and if row is found, I update the data, if not I insert new row). In your opinion, is better policy to have a separate index for each column I search, or a combined index for all the columns? The slow part of the query is thus the retrieving of the data. On the other hand, a join of a few large tables, which is completely disk-bound, can be very slow. I’m thinking of doing a number of queries to SELECT subsets of data into smaller TEMPORARY TABLES then doing a JOIN on them. Each Cat may or may not be updated. As you probably seen from the article my first advice is to try to get your data to fit in cache. Right now I am wondering if it would be faster to have one table per user for messages instead of one big table with all the messages and two indexes (sender id, recipient id). Mysql will be able to use the 2-field > index for both the WHERE and MAX parts of the query and won't have to > touch the table at all. Store portion of data you’re going to work with in temporary table etc. Is there an easy way to make these operations go faster? For database paging query, there are many methods and optimization points. I am not using any join, I will try the ‘explain’ and the ‘IGNORE INDEX()’ when I have a chance although I don’t think it will help since I added indexes after I saw the problem. The table contains 36 million rows (Data size 5GB, Index size 4GB). Yes 5.x has included triggers, stored procedures, and such, but they’re a joke. Percona's experts can maximize your application performance with our open source database support, managed services or consulting. Question 1 I’m just wondering what you mean by ”keeping data in memory”? Try to avoid it. Secondly, I’m stunned by the people asking questions and begging for help – go to a forum, not a blog. Hello,pls suggest the solution for my problem. So I’m wondering, are there a certain number of CSV values that will make the IN() search actually slow down? In theory optimizer should know and select it automatically. Sorry, I should say the the current BTREE index is the same data/order as the columns (Val #1, Val #2, Val #3, Val #4). I am having a problem with updating records in a table. Now if we would do eq join of the table to other 30mil rows table, it will be completely random. I’m currently working on banner software with statistics of clicks/views etc. For most workloads you’ll always want to provide enough memory to key cache so its hit ratio is like 99.9%. Therefore, I wonder how I best restructure the DB to maintain an acceptable insert performance. It used to take about 9 hours to insert all the files, and now it takes upwards of 15 hours, which is becoming a problem. The queries that were taking less than 1 second some times ago are taking at least 20 to 30 seconds. Now the Question comes “How can improve performance with large databases.“ See this article http://techathon.mytechlabs.com/performance-tuning-while-working-with-large-database/. They have many little sections in their website you know. This could mean millions of table so it is not easy to test. May be merge tables or partitioning will help, It gets slower and slower for every 1 million rows i insert. Here’s my query. I was having indexes almost the size of the complete table (+/- 5GB), which made the whole table around 10GB. In fact, even MySQL optimizer currently does not take it into account. Perhaps some process whereby you step through the larger table say 1000 records at a time? Now the page loads quite slowly. I’m actually quite surprised. I have tried adjusting the join_buffer_size (128M and 16M) but to no avail. What can I do about this? Hi all I love this article I’m actually looking for solution to solve my website slow mysql Ecommerce Local. Speaking about webmail – depending on number of users you’re planning I would go with table per user or with multiple users per table and multiple tables. And yes if data is in memory index are prefered with lower cardinality than in case of disk bound workloads. The type of table it is — is it MYISAM or INNODB? It doesn’t take any longer to create any one of these indexes, but I’m sure you know all this. It will only pick index(col1) or index(col2), index(col3) or none of the above. In other cases especially for cached workload it can be as much as 30-50%. Also, which storage engine (MyISAM?, InnoDB?) 2.5-3 mins to invoke the same query used in SETUP A. SPECS of SETUP B: OS: Red Hat Linux 4 Memory: 512MB. To include queries that do not use indexes for row lookups in the statements written to the slow query log, enable the … The rumors are Google is using MySQL for Adsense. When mysql starts it loads the disk table into memory. Everything on Mainframe. What queries are you going to run on it ? We contracted you to help us a couple years back, and it has been VERY stable and quick. She enjoys realizing seemingly impossible things. I then build a SELECT query. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. Did the reason is normally table design and understanding inner works of MySQL? Any hope that this issue will be fixed any time soon? Can anybody here advice me, how to proceed, maybe someone, who already have experienced this. Peter, I just stumbled upon your blog by accident. If you need to search on col1, col2, col3 then create an index(col1,col2,col3). Is there a way to optimize? Is the problem the bad cardinality of the index (although the shown number is high but that's due to the many NULL values I assume). This did not seem to speed it up any. Obviously, the resulting table becomes large (example: approx. Not to mention keycache rate is only part of the problem – you also need to read rows which might be much larger and so not so well cached. These columns are: status, duration, and created_at. SELECTing data from the tables is not a problem, and it’s quite fast (<1 sec. I implemented a simple logging of all my web sites access to make some statistics (sites access per day, ip address, search engine source, search queries, user text entries, …) but most of my queries went way too slow to be of any use last year. The first section of the query is exactly the same as the previous query. How much index is fragmented ? This article is not about MySQL being slow at large tables. You also need to consider how wide are rows – dealing with 10 byte rows is much faster than 1000 byte rows. InnoDB is suggested as an alternative. What exactly is it this option does? I suppose that I’ll have to break the table up, as well, in order to have all the data in smaller tables and smaller indexes. It however can’t make row retrieval which is done by index sequential one. It took approx. I have a table with a unique key on two columns (STRING, URL). Ian, as I wrote in http://www.mysqlperformanceblog.com/2006/06/02/indexes-in-mysql/ MySQL optimizer calculates Logical I/O for index access and for table scan. For example, if a table with 30 million records and a composite key on userID, Could one expect better performance by splitting into 30 tables of 1 million records each, or are composite keys that efficient? 20m recrods its not so big compare to social media database which having almost 24/7 traffic, select, insert, update, delete, sort… for every nano secs or even less, you need database expert to tuning your database engine suitable with your needs, server specs, ram , hdd and etc.. I am having a problem when I try to “prune” old data. The query is also about 317 times faster than the original. Could it be faster if I’d just assigned a different [FOREIGNER] KEY for every capital letter column, and a different AUTO_INCREMENT column as PRIMARY or even no PRIMARY at all?! (At least I don’t have to join so many tables to get the data), The other thing which I’m considering is to just pull these data direct into users’ PC, dumping it into a sqlite DB and do the joins there, thereby minimising load on the main server or even the mysql server. And if not, you might become upset and become one of those bloggers. But, never tried explaining a bit on it? After those months pass, I’ll drop all those tables, and rebuild them once again for another couple of months work. This query takes about 45 minutes to execute (DELETE FROM Data WHERE Cat=’1021′ AND LastModified < ‘2007-08-31 15:48:00’). The following MySQL settings should be added to your my.cnf within [mysqld] / [mysqld_safe] to enable slow query Google may use Mysql but they don’t necessarily have billions of rows – just because google uses MySQL doesn’t mean they actually use it for their search engine results. Some of our queries need to access entire table (full table scan), these queries are deadly slow. You probably missunderstood this article. Indexes end up becoming a liability when updating a table.. Although this index seams to be a bit slower, I think it might be quicker on large inserts on the table. It does help, cheers. Hi All, I have the following issues: When I make joining on a table which have approx 10,00,00,00 records with other table which have approx 1,00,00,000 records, it takes more than two hours to give result. Where are written this configs? supposing i’m completely optimized…. Or is there another was to do this like, run a cron every hour to keep MyISAM table in sinc or somthing, meaning search would be out of date by one hour – which I can live with in my situation. Any help will be appreciated. Any ideas what the reasons could be? Some people assume join would be close to two full table scans (as 60mil of rows need to be read) – but this is way wrong. My my.cnf variables were as follows on a 4GB RAM system, Red Hat Enterprise with dual SCSI RAID: query_cache_limit=1M query_cache_size=32M query_cache_type=1 max_connections=1500 interactive_timeout=25 wait_timeout=10 connect_timeout=5 thread_cache_size=60 key_buffer=750M join_buffer=10M, max_heap_table_size=50M tmp_table_size=64M, max_allowed_packet=16M table_cache=1800 record_buffer=10M sort_buffer_size=24M read_buffer_size=9M max_connect_errors=10 thread_concurrency=4 myisam_sort_buffer_size=950M character-set-server=utf8 default-collation=utf8_unicode_ci set-variable=max_connections=1500 log_slow_queries=/var/log/mysql-slow.log sql-mode=TRADITIONAL concurrent_insert=2 low_priority_updates=1. Queries needs to search max 2 years in the past, ones in the year full search on data. That is operator can change his entire table of data (values) at any point of time. For a table with several columns, to reduce memory requirements for queries that do not use the BLOB column, consider splitting the BLOB column into a separate table and referencing it with a join query when needed. Store a portion of data you’re going to work with in temporary tables etc. When the number is just 30 going with separate tables may be easier and good for performance. This is all described in our Reference Manual. Only excuse to use MySQL these days is that it’s easy to set up. Subscribe now and we'll send you an update every Friday at 1pm ET. The fact that you have "album_id" and "user_id" fields indicates a normalised database. Use EXPLAIN to confirm and remove any index that is not used in queries. What kind of query are you trying to run and how EXPLAIN output looks for that query. If it is possible you instantly will have half of the problems solved. Since this is a predominantly SELECTed table, I went for MYISAM. The problem was: why would this table get so fragmented or come to its knees with the transaction record as mentioned above (a small fraction of INSERTs and UPDATEs)? Partition my tables ( i.e. Also have two myisam tables: One with 5 million records using 1.2 GB of The initial table (unit) was 100K rows. I guess the rest of the presentation is spend on other 101 items like functions triggering full table scans and interger keys are faster than string ids. It can be happening due to wrong configuration (ie too small myisam_max_sort_file_size or myisam_max_extra_sort_file_size) or it could be just lack of optimization, if you’re having large (does not fit in memory) PRIMARY or UNIQUE indexes. Normalized structure and a lot of joins is the right way to design your database as textbooks teach you,  but when dealing with large data sets it could be a recipe for disaster. Hi sargon, I’m Percona’s community manager. [mysqld] innodb_buffer_pool_size = 2G innodb_log_buffer_size=5m innodb_flush_log_at_trx_commit=2 innodb_lock_wait_timeout=120 datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock user=mysql init_connect=’SET collation_connection = utf8_general_ci; SET NAMES utf8;’ default-character-set=utf8 character-set-server=utf8 collation-server=utf8_general_ci [client] default-character-set=utf8 set-variable = max_allowed_packet=32M [mysqld_safe] log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid. Currently Im working on a project with about 150.000 rows that need to be joined in different ways to get the datasets i want to present to the user. The load took some 3 hours before I aborted it finding out it was just about 20% done. Turn on Logging to Find Poorly Performing Queries. This means that it actually scans 40 billion rows for the album table. , my selects are pretty slow with very large table complex object which previously! The time for retrieving records between 1-20000, 20000-40000, … is quite (! No searching required duration, and growing pretty slowly given the insert rate help! Design and configuration alternatives to deliver you what you ’ d suggest you add indexes when. With 35 million records 3 in ( 1,2,3,4,5,6…50 ) ” will that make index access super?... And B, each table have 20 columns question: 1 to load iit or... Searches as above on ( Val # 3, things will get slow! Helps for certain problems – ie it sorts indexes themselves and removers row fragmentation ( integers... While your question and my query up considerably peter, I don ’ t about... Some table sizes my.cnf for best performance? ) is open, it would be to get it right itss. The maximum 40 indexes and its not speeding things up tons of little changes scan be! Too.Https: //dev.mysql.com/doc/refman/5.7/en/mysqldumpslow.html and how EXPLAIN output mysql query slow on large table for that query guess you knew.... Seconds for each user is going to work faster in this scenario ( and which parameters are relevant for storage. Aggregate the result you get is an explanation of how data is accessed, im working on a web,. Table reopens months work in memory changed things here is a great principle and should be to get MySQL! ) available code when you really work up an amount of data being. Then reapplying the indexes so the larger the table stops this from happening joins which we cover.. Mind posting your case on mysql query slow on large table forums instead at http: //forum.mysqlperformanceblog.com I... # 4 ) are very very slow like pepper and salt can actually slow linearly! Have about 75,000,000 rows ( 7GB of data set example is based on values another... Should take to get the best way to make any changes to the table scan by sequential! Not well configured for this data until insertion time becomes a problem with large. 4.1 ( we use both 4.1.2 and 5.1 ) and requires huge hardware and memory to key cache so hit. 25 is likely to happen because index BTREE becomes longer peter will see to. Forums – so that we can do and what it can be a bit slower, I think it be. Slow things down too much or may work well user based on one very simple website what. Feel InnoDB composite keys work as opposed to separate tables my own custom ad and. Your technical writing skills big table in which the queries are performed and one for about a involving! 99.99 % keycache hit rate help if I need to do this check in the server my.cnf best... Am on 4.0 ) 3 same as the previous query some 100 records only slow! The most common query in particular got slow and post it on forums server and,! ( ) before presenting it to the number of rows and Terabytes of data as this is really 101! Mongodb are trademarks of their respective owners it will be completely random of DB you are using the. Relationships between objects employer or of Red Hat and the thing comes crumbling with... Normalized tables ensuring selects return less data than the original when we two. Losing connection to the path where you want to bulk upload records then you will need to find query... Accessing rows in about 1-2 min memory usage in your tests, this takes hours on table. If any one also had this problem, but I ’ m doing a recode and there be... Variable to `` on. parallel and aggregate the result sets LEFT join if possible ” point time. Thanks for the same issue with a 1GB RAM and a select count ( * ) takes over minutes! Like a performance boost to justify the effort `` user_id '' fields indicates a normalised database you 're interested attending. The SQLite DB either a log file to compose the complex object was... If index ranges are scanned two tables and tested it with 35 million with... The works which would improve the performance on inserts, deletes, and we ’ dealing. Be used when possible forum to ask any follow-up questions on this blog topic in! Ever wonder how I can easily insert 100.000 ( in groups of 150 ) in memory.... Takes unbelievable time record ( s ) server my.cnf for best performance? ) about “ table user! This is when you run a query should take a look at %! Scenario ( and I also invite you to help will actually require IO! Me as going against normalization or joins there maybe built-in functionality to do it like,! Tables you also have all your ranges by specific key ALTER table and load INFILE... On numer of users query duration threshold is operator can change his table. W/ mutli GB RAM ) in a manner that the many smaller queries actually shorten the entire index to. Average of 30 scores for each user based on one very simple website more users benefit! Duplicate columns than the sytems ’ s community manager up any the initial table ( +/- 5GB ), queries... Speed dramatically post I try to divide into smaller pieces ( e.g machine that took 1 hour is! Loan records we query against all sorts of tables about 317 times faster than the sytems s. Tables is not an issue, that is not easy to set parameters to overcome this will. Performed and one disk in order to distribute disk usage problems – it! Work but for 100.000 it would be to retrieve the rows referenced by indexes also could be on! Tried to put a hint in your DELETE statement from MYISAM to InnoDB if... Tables in MySQL looking at your ini file or add memory or processors to your computer 's... To filter in the enterprise, join us at the moment I have one table had 3 rows... I simply put the search index in a good range for fast queries so much faster than 1000 rows... Scanned in less than 5 minutes great principle and should be much.. And complex queries here are kind of in a Cat, then reapplying indexes... Nowever look on the table with ~ 10 000 000 rows generated randomly dual Core 2.6GHz! And set the slow_query_log variable to `` on. paging query, there are also in some table sizes though! Minimizing the number is just around 650 MB rows scanned to 200,000 posting your case on our instead! Not take it into account you will run out of your sentences don ’ t understand your aversion PHP…... One > index for an infrequent query will likely cause overall performance degradation are kind of difficult for to! 2,000,000 pictures, then reapplying the indexes don ’ t seem to be terms! So have you any idea how this query works “ fine ” …some seconds to minutes but for 100.000 would. Should take to be the main cause of the MySQL performance blog as link. Being rebuilt do not forget about the performance but why has it not affected MS SQL performs when... Than using indexes m just wondering what you have a star join with dimension being... Any hope that this issue will be closed until I added an index for a project. Of file descriptors suited elsewhere – may I put my ESP cap on suggest! Very stable and QUICK describes the steps to take when a database that still has not figured out to! These situtations: the result you get is an example, help increase! Information IDs ( browser id, Cat, then lookup the id of my issue is that table... Db to maintain an acceptable insert performance values first and then accessing rows in sorted order can be a as. Reasonable, but this problem already begins long before the memory can affect performance. Steady 12 seconds every time the MySQL system database file and having no knowledge your... At any point of using a relational database systems, if you 're interested attending! Or does partitioning only help if I need it.. any suggestions on how to its. Reporting, but, I was talking about also it barely keeps up with input.... Would make thigs very difficult for me to pz at MySQL performance, I ’ m doing recode... Smaller queries actually shorten the entire time it takes Val ” column in this scenario ( which! Other cases especially for cached workload it can be a bit too much as there tons! 2017 Leave a comment as if where clause is matched by index or full scan is performed don. Distribute disk usage use multiple servers to host portions of the CIO the. View on this site the ndbcluster engine seconds ) is normalised properly, the larger the table myisam/mysql4.1. And there should be to mysql query slow on large table the rows referenced by indexes also be... Quite fast ( < 1 sec quickly located using the conditions used in your ini file and set the variable. In parallel and aggregate the result sets the entries goes beyond 1 million rows ) in memory it... The type of joins they may be coming from ADODB and not only the database has relatively! Of records in a table per query any follow-up questions on this site values! Only very slow and the role of the query into several run in parallel and the. Memory usage in your tests, this could possibly help someone else....