SQL_CALC_FOUND_ROWS is used in most queries in order to implement pagination, even when you don’t need pagination at all. The query is blazing fast. I’ve seen at least one slow-log for MySQL that is FULL of SQL_CALC_FOUND_ROWS queries from a large WordPress installation on a dedicated server that took 11-15 seconds per query (and crashed MySQL, repeatedly). r/mysql: Discussion of MySQL and assistance for MySQL related questions. Depending on the size of the result set this may only process a marginal ammount of the database. When using a LIMIT the query halts as soon as the max-limit is reached. I tested this on an application a few months ago and found the same: SQL_CALC_FOUND_ROWS was always much slower than two queries. Counting millions of rows in MySQL is slow. The graphs show that using SQL_CALC_FOUND_ROWS is virtually always faster than running two queries that each need to look at actual data. SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name WHERE id > 100 LIMIT 10; SELECT FOUND_ROWS(); as you can tell it’s nice and simple way to check total number of results from MySQL. The general consensus is that running a secondary query … * The count() method in MySQL is notoriously slow * (http://mysqlha.blogspot.com/2009/08/fast-count-for-innodb.html) as it scans the entire index. This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. © 1995, 2020, Oracle Corporation and/or its affiliates. It does not make sense to use SQL_CALC_FOUND_ROWS in a query that does not have a LIMIT clause. Here is what you need to know about MySQL ORDER BY LIMIT optimization to avoid these problems. This seems to be a very slow mySQL call and it would be great if there was a way to speed the pagination of the site up by using a more efficient call #11 @ scribu 9 years ago. The default MySQL query indexing on OpenCATS clearly sucks, as I have one user that's seeing a slow query of 50 seconds everytime they hit the candidates tab. How to repeat: explain SELECT SQL_CALC_FOUND_ROWS v.ID , MATCH (v.title, v.description) AGAINST ("gezielt und … 2. Support » Topic Tag: SQL_CALC_FOUND_ROWS. In a search page, the results are often paged (for example a website could display 10 results per page, just like Google). 0. 3 years ago. Is 1.5 seconds fast or slow for 15K rows returned? Sorry, you can't reply to this topic. 2. In cases where you are comparing a non-indexed column, SQL_CALC_FOUND_ROWS should be twice as fast compared to running a second query with COUNT(*) . Suboptimal MySQL ORDER BY implementation, especially together with LIMIT is often the cause of MySQL performance problems. Read more on 'How Mysql optimizes WHERE and ORDER'. SQL_CALC_FOUND_ROWS is causing my server to become unresponsive every day or two. Quote possibly that is the time it takes to shovel several megabytes out of the MySQL server, across the network, and into the client. MySQL has a nonstandard query modifier called SQL_CALC_FOUND_ROWS. There is a lot to do in order to optimize Pagination queries. It is not reviewed in advance by Oracle and does not necessarily represent the opinion The main table has about 850,000 records in it. MySQL ORDER BY with LIMIT is the most common use of ORDER BY in interactive applications with large data sets being sorted. When in use on a SELECT with LIMIT, it attempts to calculate how many rows would have been returned if the limit were not there, and then store that for later retrieval in FOUND_ROWS(). I've seen many old articles from before 2011 saying to never used this as part of your approach to pagination because it's very slow. Now when I remove SQL_CALC_FOUND_ROWS , Group By and Having Part of the query. -- Following, > up with a count(*) query only takes 7.67 seconds, and that is much, > better performance for my needs, but the SQL_CALC_FOUND_ROWS seems. New Topic. Sounds like an un-optimized where query, the joins are most likely not the problem. Sounds like an un-optimized where query, the joins are most likely not the problem. Topic Tag: SQL_CALC_FOUND_ROWS Topic; Voices; Replies; Last Post; WordPress: SQL_CALC_FOUND_ROWS, MySql query slow my site? SELECT SQL_CALC_FOUND_ROWS * FROM TEST LIMIT 2; SELECT FOUND_ROWS (); When you execute the above, it returns two result sets. SELECT SQL_CALC_FOUND_ROWS * FROM city IGNORE INDEX(PRIMARY) ORDER BY id DESC LIMIT 100000, 15; If you need further information of when to use SQL_CALC_FOUND_ROWS and when not, take a look at the article on MySQL Performance Blog. Following up with a count(*) query only takes 7.67 seconds, and that is much better performance for my needs, but the SQL_CALC_FOUND_ROWS seems like a good idea, any ideas on optimizing either of these queries? Is SQL_CALC_FOUND_ROWS still slow? The reason appears to be that MySQL does a good job of optimizing LIMIT queries by stopping them when the desired number of rows has been found. The first result set will return two rows. Tables "mail_links", "mails" are MyISAM and "clubs" are InnoDB. If you just need a matches count and a smaller result SQL_CALC_FOUND_ROWS is probably perfect but you must have friendly indexes and WHERE clauses as it reads the entire table. iterating it. Seesm to be odd, as there's a single user experiencing this. As the database gets bigger, the speed advantage of SQL_CALC_FOUND_ROWS increases. When using COUNT or SQL_CALC_FOUND_ROWS with a WHERE the mysql server has to process every row. A simple google for “SQL_CALC_FOUND_ROWS” will reveal page upon page of complaints about speed and and comparisons between using it or running an secondary query instead using COUNT(*). *

* The rules are: *

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    I'm running mysql 5.0.45 on debian. The solution is SQL_CALC_FOUND_ROWS.This is usually used when you are selecting rows but still need to know the total row count (for example, for paging). sql_calc_found_rows ¶ Adds the SQL_CALC_FOUND_ROWS hint, which means the total count of matching rows will be calculated when you only take a slice. SQL_CALC_FOUND_ROWS has a number of problems. The other way to do that is just run it like that: SELECT COUNT(pk) FROM tbl_name WHERE id > 100; Which is bit more complicated if you have queries like that: SQL_CALC_FOUND_ROWS 785 #define SQL_NO_CACHE_SYM 786 #define SQL_SMALL_RESULT 787 #define SQL_SYM 788 #define SQL_THREAD 789 #define SSL_SYM 790 #define STACKED_SYM 791 #define STARTING 792 #define STARTS_SYM 793 #define START_SYM 794 #define STATS_AUTO_RECALC_SYM 795 Mike Hillyer www.vbmysql.com -----Original Message----- From: Jeremy Zawodny [mailto:Jeremy@stripped] Sent: Wednesday, April 16, 2003 3:59 PM To: Mike Hillyer Cc: mysql@stripped Subject: Re: SQL_CALC_FOUND_ROWS is very slow On Wed, Apr 16, 2003 at 03:40:46PM -0600, Mike Hillyer wrote: > Hi All; > > Has anyone every used SQL_CALC_FOUND… of Oracle or any other party. > a good idea, any ideas on optimizing either of these queries? Depending on your table’s indexes, the columns used inside of the WHERE condition, and based on how the result is being ordered, using SQL_CALC_FOUND_ROWS could actually be much slower. Inside \WP_Query and get_posts() it is done with the arg no_found_rows => false. Slow Mysql Queries. From MySQL Doku: "It works by performing the search twice, where the search phrase for the second search is the original search phrase concatenated with the few most highly relevant documents from the first search." It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party. On many web sites, you will … What do you think? LIMIT 50 was about 3 times faster than doing: SELECT SQL_CALC_FOUND_ROWS * FROM mytable WHERE ... LIMIT 50 SELECT FOUND_ROWS () so it is probably not worth using on large tables until this bug is fixed. How are multiple Wordpress WPDB queries handled? Depending on the size of the result set this may only process a marginal ammount of the database. mysql> SELECT SQL_CALC_FOUND_ROWS * FROM wd WHERE affiliationid = 0, mysql> EXPLAIN SELECT SQL_CALC_FOUND_ROWS * FROM wd WHERE affiliationid. Wordpress plugins for database queries. Hi All; Has anyone every used SQL_CALC_FOUND_ROWS? if i run the query without sql_calc_found_rows the execution time is 0.7 secs You can access this count with the found_rows attribute of the QuerySet after filling its result cache, by e.g. Content reproduced on this site is the property of the respective copyright holders. Jeremy D. Zawodny | Perl, Web, MySQL, Linux Magazine, Yahoo! > I use it in an indexed query, and my retrieval time goes from 0.13, > seconds to 30.13 seconds, this is a serious performance hit. Even when using MyISAM. First of all, it's slow. Using SQL_CALC_FOUND_ROWS defeats this optimization. 'Matched' union select DIST_NO from transfrd WHERE FOLIO_NO='l01917' And STAT_FLAG <> 'Matched' LIMIT 0, 5; The above query takes more than 4.5secs. mysql_query ( "SELECT SQL_CALC_FOUND_ROWS `aid` From `access` Limit 1" ); This happens while the first instance of the script is sleeping. 4. SQL_CALC_FOUND_ROWS is even slower and Laravel loves to count with its Paginator. * * In the WP_Query class this stops the use of SQL_CALC_FOUND_ROWS in the * MySql query it generates. Slow SQL_CALC_FOUND_ROWS Query. > Has anyone every used SQL_CALC_FOUND_ROWS? * SQL_CALC_FOUND_ROWS was introduced to allow clients to obtain a count() * in a more performant way. mysql> SELECT * FROM wd WHERE affiliationid = 0 ORDER BY productgroup, mysql> EXPLAIN SELECT * FROM wd WHERE affiliationid = 0 ORDER BY. Memory and slow when it is fast when the index data is in memory and slow when it is with! The arg no_found_rows = > false to MySQL to do additional work for counting the matching! 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