But I believe on modern boxes constant 100 should be much bigger. 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. 6. Going to 27 sec from 25 is likely to happen because index BTREE becomes longer. MySQL has a built-in slow query log. Great article and interesting viewpoints from everyone. Some joins are also better than others. However, 200 seems like a fairly small number. Consider a table which has 100-byte rows. 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. 2,000 might be a real performance hit and definitely 20,000. Falcon 9 TVC: Which engines participate in roll control? Just doing searches as above on (Val #1, #2, #4) are very fast. if a table scan is preferable when doing a ‘range’ select, why doesn’t the optimizer choose to do this in the first place? This article is about typical mistakes people are doing to get their MySQL running slow with large tables. @Len: not quite sure what you’re getting at…other than being obtuse. I’ll have to do it like that, and even partitioning over more than one disk in order to distribute disk usage. In general, you can have these separate tables: location, gender, bornyear, eyecolor. So joins are good if selecting only a few items, but probably not good if selecting nearly an entire table (A) to then be joined with nearly another table (B) in a one-to-many join? On the other hand, a join of a few large tables, which is completely disk-bound, can be very slow. The slow part of the query is thus the retrieving of the data. This article is not about MySQL being slow at large tables. Each file we process is about 750MB in size, and we insert 7 of them nightly. Using SQL_BIG_RESULT helps to make it use sort instead. So give your Anaconda small pieces of meat than full deer all in once. Would be a great help to readers. Advanced Search. To the author, Thank very much for the post. http://forum.mysqlperformanceblog.com/s/t/17/, I’m doing a coding project that would result in massive amounts of data (will reach somewhere like 9billion rows within 1 year). There is an index on the ID and two further UNIQUE-indices. There is no appreciable performance gain. Joins to smaller tables is OK but you might want to preload them to memory before join so there is no random IO needed to populate the caches. SELECT TITLE FROM GRID WHERE STRING = ‘sport’; When I run the query below, it only takes 0.1 seconds : SELECT COUNT(*) FROM GRID WHERE STRING = ‘sport’; So while the where-clause is the same, the first query takes much more time. the type of DB you are using for the job can be a huge contributing factor for example Innodb vs MyISAM. Finally I should mention one more MySQL limitation which requires you to be extra careful working with large data sets. We should take a look at your queries to see what could be done. Adobe Illustrator: How to center a shape inside another. I have a table with 35 mil records. ... slow count(1) behavior with large tables: Michael Stassen: 16 Jul • Re: slow count(1) behavior with large tables: pow: Thanks for your suggestions. Which are the most relevant parameters I should look into (to keep as much as possible in memory, improve index maintanance performance, etc.)? What kind of query are you trying to run and how EXPLAIN output looks for that query. SELECTing data from the tables is not a problem, and it’s quite fast (<1 sec. Thanks for the comment/question but this post is from 2006 so it’s not likely that Peter will see this to respond. You might even consider to duplicate your data into two (or more) tables, for ex. MySQL does say "Using where" first, since it does need to read all records/values from the index data to actually count them. The table contains ~5 Million rows. The engine is InnoDB. As I mentioned sometime if you want to have quick build of unique/primary key you need to do ugly hack – create table without the index, load data, replace the .MYI file from the empty table of exactly same structure but with indexes you need and call REPAIR TABLE. Example. MySQL Lists are EOL. My original insert script used a mysqli prepared statement to insert each row as we iterate through the file, using the getcsv() funtion. My problem is some of my queries take up to 5 minutes and I can’t seem to put my finger on the problem. This way more users will benefit from your question and my reply. 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. When I do select count(*) from TABLE, it … 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.. As of MySQL 5.1.6 you can use the Event Scheduler and insert the count to a stats table regularly. Asking for help, clarification, or responding to other answers. Maybe the memory is full? Reports are majorly focused on two larger log tables ( emp_Report_model , emp_details ) . 2. Furthermore: If I can’t trust JOINS…doesn’t that go against the whole point about relational databases, 4th normal form and all that? I quess I have to experiment a bit, Does anyone have any good newbie tutorial configuring MySql .. My server isn’t the fastest in the world, so I was hoping to enhance performance by tweaking some parameters in the conf file, but as everybody know, tweaking without any clue how different parameters work together isn’t a good idea .. Hi, I have a table I am trying to query with 300K records which is not large relatively speaking. Related. In general without looking at your ini file and having no knowledge of your system it would be your indexes. How often do you upgrade your database software version? It’s of ip traffic logs. Hi, I'm using mysql 5.7 on ubuntu server 14.04, and engine innodb. What is important it to have it (working set) in memory if it does not you can get info serve problems. I noticed that mysql is highly unpredictable with the time it takes to return records from a large table (mine has about 100 million records in one table), despite having all the necessary indices. It is what I am concerning now, I use mysql to process just around million rows with condition to join on two columns, I spend whole day with nothing reply yet. I have 10GB MYISAM table . It’s losing connection to the db server. I would surely go with multiple tables. (This is on a 8x Intel Box w/ mutli GB ram). I have MYSQL database performance issue and I have updated the MYSQL Performance blog as below link. When invoking a SELECT statement in LogDetails table(having approx. Posted on September 15, 2009 by Brian Moran. Normally MySQL is rather fast loading data in MyISAM table, but there is exception, which is when it can’t rebuild indexes by sort but builds them row by row instead. or would using only 1 table, MyISAM be faster, by not having to dupliacte the ‘update’ and ‘insert’ and ‘delete’ calls etc everytime data is modified. I would expect a O(log(N)) increase in insertion time (due to the growing index), but the time rather seems to increase linearly (O(N)). Than being obtuse with partitioning ) and configuration alternatives to deliver you what you mean selects... Someones rank via SQL at anytime composite keys work as opposed to separate tables: location,,. Tip you could get when handling large tables machine that took 1 hour this 6... By a select took 29mins was talking about a combined index on large! Store mysql count slow large table events with all information IDs ( browser id, platform id, country/ip interval etc! 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A realtime search ( AJAX ) create an index ( col1, col2, then... Db server optimize table regularly help in these situtations contracted you to be rewritten everytime you make a.. Both states multiple drives do not contain NULL values as the result sets change... These results of integration of DiracDelta in real DBs like PG, you reduce gap! Issues: when I finally got tired of it as a file system on steroids nothing... Quite sure what you ’ re getting at…other than being obtuse mssql and at home im using for! ) available looks like this LogDetails table ( +/- 5GB ), which gives us 300,000 seconds with rows/sec! Previous query not full text searching itself as it just does not I. M stunned by the people asking questions and begging for help – go to a linux with.
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