Mysql query slow. But first, you need to narrow the problem down to MySQL.
I noted that the original query was fast when the number of selected rows was greater than the limit parameter. Apr 22, 2022 · 3. I am running the following query: SELECT DISTINCT orders_id. Slow_launch_threads. Dec 29, 2022 · In this article, we’ll walk through five ways to quickly improve your MySQL database performance. 1) some cases of UNION ALL were improved to deliver the data from one SELECT straight to the client, then deliver the others. answered Jan 27, 2017 at 18:21. The slow query log consists of SQL statements that take more than long_query_time seconds to execute and require at least min_examined_row_limit rows to be examined. Given is a mySQL table named "orders_products" with the following relevant fields: Both fields are indexed. Aug 16, 2022 · The MySQL slow query log is a debugging option which can help you identify suspect SQL statements, providing a starting point for your investigations. UPDATE: Ok, a few Nov 4, 2010 · 3. Changing the size by a small amount has only a minor May 1, 2017 · MySQL has a built-in slow query log. In one area of my application, "load data infile" goes quick. 23 has still slow speed issues. Short of creating an additional table in the database and manually updating it every time the database is updated, is there another solution that can give me fast results. My query performance really deteriorates when trying to filter on the primary key column. Aug 13, 2013 · With UNION ALL, the temporary table is created, but without the index. from transaction_batch. speed up query with a lot of like clauses. Improving database performance in general. I'm not sure why MySql hasn't sped up OFFSET but between seems to reel it back in. Oct 8, 2012 · The ALTER TABLE involves copying over all the data from the table and recreating the indexes. Changing the ORDER BY to the primary key id makes it slow too, but still 10x as fast as with the indexed isbn field. The only problem is that in a stock MySQL, it can only be set in increments of 1 second, which is too slow for some people. Changed the engines for all tables in both databases from InnoDB to MyISAM with optimization. Jul 29, 2016 · The first query would still use the index and perform as expected. Your actual problem is that it is not possible for MySQL to use an index for a condition such as myindex LIKE '% keywords1 %'. It is used to enable additional fields in the MySQL slow query log. 5, “The Slow Query Log”). As a first measurement try copying the data file (item_catalog_map. It's not impossible on a slow server for index creation ona large table to take an hour or more. log ; Set the timeout (in seconds Jul 1, 2010 · Slow_queries. 10. To choose the slow query log output destination, set the log_output system variable. log'; but your changes will be undone when mysql is restarted. 1. log_slow_verbosity ‘full’ Jul 17, 2012 · Using the MySQL CLI client the user select query doesn't even take measurable time - it's done before I've even let the return key up. Any new connection I open (in the same workbench) has the same issue Aug 26, 2020 · I'm using WAMP on a Windows 10 (i5,ssd) machine and noticed the websites are quite slow. Feb 1, 2023 · Check if the MySQL slow query log is enabled. WHERE products_id = 85094. FROM orders_products. 388 seconds query time using InnoDB engine. This worked fine until I got past page 100 then the offset started getting unbearably slow. However, coding around this with an alternate query adds an Jul 26, 2016 · If you want to optimize further, the next thing to do is to move the nlikes and date columns into the users_face table, then make the index on that table over the following columns in this order: (fb_id, token_valid, date, nlikes). WHERE product_id IS NOT NULL AND product_id > 1. table: me. The MySQL slow query log contains information about queries that take a long time to execute (see Section 5. Enter the MySQL shell and run the following command: set global slow_query_log = 'ON'; 2. Slow queries on indexed columns (large datasets) 0 Why does this sql join query take much longer using a reference to a row from the first table in the 'on' clause versus using a literal variable? Mar 14, 2014 · MySQL slow query log. r3. 1, 5. ; Activate the slow query log. I think that the performance of IN clauses like that must vary a lot from server to server. Normally, mysqldumpslow groups queries that are similar except for the particular values of number and string data values. You can do this from a MySQL shell session: sudo mysql SET GLOBAL slow_query_on = "On"; SET GLOBAL slow_query_log_file = "/slow-query. Subsequently, MySQL records these slow queries in logs called slow query logs. Your system probably was "swapping". The best way to improve the performance of SELECT operations is to create indexes on one or more of the columns that are tested in the query. The server was running MySQL 5. ) Several benefits as bugs have been corrected, the optimizer improved and you can set the low threshold for slow queries to less than 1 second (like 10 milliseconds). Enabling the Slow Query Log The log is a built-in mechanism for recording long-running SQL queries. , much slower for large lists). But when I add database queries in a loop, it's the opposite: Win10: 147 sec Win7: 15 sec. In this article, we'll discuss various ways to identify poorly performing queries in MySQL databases. The number of threads that have taken more than slow_launch_time seconds to create. Jul 11, 2013 · 3. This section discusses these optimizations, particularly with regard to the challenges that NULL values present. where status_id IN (1,2) group by status_id. More precisely Duration / Fetch = 0. If Feb 1, 2010 · The main considerations for optimizing queries are: To make a slow SELECT WHERE query faster, the first thing to check is whether you can add an index. These slow query logs are a crucial tool to help you analyze and optimize your database performance. This variable is available only for debug builds of MySQL. ) 6 days ago · The more selective your query, the faster it will be. Jun 6, 2010 · 7. In this blog post, I’ll cover the Apr 8, 2024 · If log_slow_rate_limit 1 - randomly log every 1/ log_slow_rate_limit query. Certain optimizations are applicable to comparisons that use the IN (or =ANY ) operator to test subquery results. 252 seconds on the laptop. In your case you can try with. The database is not very busy otherwise, and performs well on other queries. 5 The Slow Query Log. First, check if query profiling is enabled by typing: SELECT @@PROFILING; +-------------+. This query takes extremely long, around 20 seconds. #2 and #3: Check up on MySQL storage engines and schema design. Check the running threads, to see if there are difference between prod and local: SELECT * FROM INFORMATION_SCHEMA. 0. BhatiaVJ Jun 14, 2012 · Finally, you claim 'empty' results are slow, however you don't explain why the empty results are empty, is it empty because one of the joins was empty, or because one of the coordinates didn't match (and if so, the world_block, or world_chunk coordinates). Select * from tblphotos yields a response in 1 second, returns 3500 rows Select * from tblphotos where ActLogId = 20992 yields a response in 130 seconds, returns 6 rows. Improve this question. select_type: SIMPLE. You can set it permanently, by adding the following to your my. For example: May 16, 2024 · In this tutorial, you’ll learn how to improve MYSQL performance. MySQL index creation, if it has to swap to disk, can take a loooong time, especially on hardware with insufficient RAM or slow disks, or when MySQL is configured to be stingy with its use of RAM from the OS. Aug 20, 2015 · The MySQL Query Optimizer can change the query execution plan on changed data always the case with JOINS. Jan 28, 2020 · However, my Mysql 8. 4. select * from entry where session_id in. This is the time the ALTER TABLE will at least take. In an another area, the select queries are VERY slow. May 9, 2013 · Some instrumentation revealed that this was entirely down to one SQL query: SELECT TABLE_NAME AS name. We use MySQL from Amazon RDS running on db. Much slower than on my old Windows 7 (i3,hd) PC. After scouring through different threads and trying different things, it worked well when I set the @variable to be of exactly the same type and same encoding as the column in the table(s) that I am searching for that variable. When I'm trying to execute query that selects points that are spatially near to the query points, total execution time takes too long. mysql. #4 and #5: Indexes and partitions. If so, skip to the Converting data into information section. I ran into a similar issue. Add index (profile_id, landing_page, all_impressions) and post an EXPLAIN if the query is still slow. Jan 31, 2017 · What helped for me was changing the engine from 'innodb' to 'myisam'. The higher is this value, the longer the query runs. Changing that to BETWEEN in my inner query sped it up for any page. 17 163. Jun 9, 2011 · 5. Deleted multiple indexes. Apr 7, 2014 · The MySQL slow query log is a log that MySQL sends slow, potentially problematic queries to. mysql: double condition WHERE LIKE slows down SELECT query. You may try the following: Explain you sql in prod and local, check whether the output is the same. You absolutely should use a SQL sort rather than a code sort where possible so you are on the right track there. In this case looks like the plan is a bit different but I have others like this: Mar 29, 2012 · Slow MySQL query when using LIKE operation on large table. Writing the Slow Query Log to a File. user2524079. cnf file: Feb 11, 2023 · Have this rather simple SELECT on just one table: SELECT id AS price_id. This question is tagged "mysql" so maybe that's what you're referring to. The Table Design is: Now I want to query a normal query: (`trackID1` = 168123 OR `trackID2`= 168123) The Explain statement gives me: The query seems to be very slow (about 185 seconds), but i don't know if it is only because of the amount of items in the table. Shut down the Atlassian applications which use the suspected MySQL server. For information about that log, see Section 7. My update query on a similar size dataset went from 100 ms to 0. . The slow log is a way of filtering the log so that we can see the ones which take a long time (most queries Oct 26, 2010 · How can I view mysql slow_query_log to see which query is taking too much time? mysql; Share. Table is innodb with 3. I've generated a database and installed our app but its a clean database and therefore difficult to generate enough problems. FROM information_schema. 21, the minimum value is 0 for long_query_time, and the value can be specified to a resolution of microseconds. This has always been a very frustrating problem with MySQL, something that Oracle managed to get right several decades ago. With query sampling this ensures that queries with longer execution time will always be captured by the slow query log, avoiding the possibility that infrequent slow queries might not get captured at all. As soon as I was sorting the resultset by a field from a joined table, the whole query was horribly slow and took more than a hundred seconds. projects -> hasMany -> milestones -> hasMany -> tasks. All subsequent queries (in the same connection) work just fine. Jan 29, 2014 · 1. The MySQL slow query log is where the MySQL database server registers all queries that exceed a given threshold of execution time. Here is the benchmark result loading 60M rows x 16 columns from MySQL to pandas DataFrame using 4 Oct 24, 2012 · Try to get rid of JOINS as much as possible. It took 89. For example, if you set the value to 100, then one percent of sessions/queries will be logged. Slow_queries. They will help you get more information about the query and its statistics. For more information on this, see the following entry on the MySQL performance blog: Mar 15, 2023 · Every MySQL 8 minor release comes with a good number of bug fixes as well as exciting new features. MySQL Query Optimizer can access the tables in the wrong order note this is not bad when you dont use GOUP BY or ORDER BY. There are some tried and tested methods to weed out slow queries. This counter increments regardless of whether the slow query log is enabled. The workloads that generate temporary objects in MySQL for query processing can take advantage of the instance store for faster query processing. 30 (query takes 12 seconds): The two tables in question are identical on both servers. With an argument of 0, this option disables the log. This logs all those queries which take more than x seconds to execute. Most heavily used production servers execute far too many queries to log them all. This approach can drastically enhance query performance. I'm trying to figure out how to optimize a very slow query in MySQL (I didn't design this): Comparing that to a full count: The explain statement doesn't help me here: explain SELECT COUNT(*) FROM change_event me WHERE change_event_id > '1212281603783391'\G. 6 and above: 1. The slow query log can be used to find queries that take a long time to execute and are therefore candidates for optimization. 1 ms. 010s. Jul 9, 2024 · slow_query_log_always_write_time: 1: Specifies which queries should ignore sampling. May 14, 2020 · Example 1: JOIN product_to_vehicle ptv USING (product_id) This query yields the following explain: MySQL 8. Any band less popular than that, the query is fast. Why does this take so much time. 2. As noted, in this case, Ctrl-C doesn’t help. Jul 30, 2015 · 235. Real-World Examples of MySQL Query Optimization. score index, it's super-fast for popular bands like "pink floyd", but then slow for less popular bands like Nov 25, 2018 · I use MySQL Workbench and @variables are very useful to query/search different tables for a given attribute. 6. Here are some common examples: Log details for queries expected to retrieve all rows instead of using an index: Dec 23, 2010 · From High Performance MySQL: Not so in MySQL, which sorts the values in the IN ( ) list and uses a fast binary search to see whether a value is in the list. Once the slow queries start logging in the log. Then you can skip the join in your query, and the sort order will be the order of the index, so that will be Apr 11, 2013 · Consider moving to a newer version of MySQL, 5. 5, “The Slow Query Log” ). Jul 16, 2013 · The query is only slow when searching very popular bands like "pink floyd" down to "coldplay". File output, table output, or both can be selected. The query cannot go right to OFFSET because, first, the records can be of different length, and, second, there can be gaps from deleted Query 3: Select count(*) as total from mybigtable where account_id=123 and email IN (select distinct email from mybigtable where account_id=345) takes 22 minutes and 90% its in the "preparing" state. Mar 23, 2021 · Enabling the slow query log gives you insight into poorly performing queries. Jul 10, 2020 · In other words, authentication talks to the database as does a simple delete query without authentication. adding an AS. You can use either one internal (indexes in MySQL) or external (Sphinx, Lucene, etc. 0. LIMIT 200. To specify the log destination, use the log_output system variable (as May 7, 2017 · We have this query which takes around 50s to finish which I think it's too slow. In Percona Server additional statistics may be output to the slow query log. Oct 3, 2010 · 10. To improve selectivity, ensure your queries filter data as precisely as possible and consider using indexes on columns that significantly reduce the number of rows processed. 5 or even 5. That in itself shouldn't be a problem here, as a full table scan of 7000 rows shouldn't take long. Enable any other desired options. For slow ORDER BY queries for which filesort is not used, try lowering the max_length_for_sort_data system variable to a value that is appropriate to trigger a filesort. MySQL 8. Slow queries can delay data retrieval, page rendering, and any other operations that interact with the data layer. The author of this question mentions that it’s usually only after MySQL prints its output that he realises that the wrong query was executed. log"; SET GLOBAL long_query_time = 5; This configuration will log any queries that take longer than five seconds to run into /slow Sep 22, 2017 · I've included the actual queries and the EXPLAIN in 3 scenarios below. Sort_merge_passes Sep 16, 2009 · Until recent versions, all UNIONs involved a temp table to collect the results, hence UNION was necessarily slower than two separate SELECTs. large and MySQL version MySQL 5. Follow asked Oct 26, 2010 at 7:43. 1. log". ). This type of workload includes queries involving sorts, hash aggregations, high-load joins, Common Table Expressions (CTEs), and queries on unindexed columns. 7. g. The inner query runs very fast (less than 0. It's normal that higher offsets slow the query down, since the query needs to count off the first OFFSET + LIMIT records (and take only LIMIT of them). Mar 29, 2012 · 2. Set it to whatever you like. For some reason, the query takes 10+ seconds to run. Be aware that changing the engine type for an existing application might have consequences as InnoDB has better data integrity and some functions your application might be depending on. answered Oct 8, 2012 at 2:51. When I loop a simple script with a calculation: Win10: 0. cnf file. Through some trial-and-error, I discovered that if I force the query to use the tblcontent. The issue must be PHP's connection to MySQL - that's as far as I've been able to reason. Sep 3, 2018 · Your query is slow not because of CASE. I would need it to work across multiple MySQL Sessions. (A symptom of setting the value of this variable too high is a combination of high disk activity and low CPU activity. The query is meant to grab all entry's that Jun 6, 2010 · 7. You need to turn on slow query log. 7, MariaDB 10. This allows flexible setup logging behavior. The is extremely detrimental to MySQL performance. innodb_buffer_pool_size = 1500M is about all that can be safely done in a "small" 4GB machines. MySQL slow query log is great at spotting really slow queries that are good candidates for optimization. 3 Optimization and Indexes. I've tested the following seemingly simple query on MySQL 5. Oct 21, 2015 · Also table_1 could be a slow sub-query. Introduction to MySQL slow query logs. AND search_name_updated IS NULL. slow_query_log = ON ; Set the location of the slow query log. What queries are logged is determined by customizable server variables that allow for query profiling based on an application’s performance requirements. Se the query became extremely slow when the limit parameter was useless. 1 seconds) to get two ID's, one for status 1, one for status 2, then it selects based on primary key so it is indexed. | @@profiling |. x is specified by you in mysql. One of the first things you may want to do when trying to optimize a slow query is to profile the query to discover where exactly the query is taking the most time. But as null values are not indexed, the index cannot be used to check the or field4 is null condition, so it would fall back to a full table scan. 14 introduced the new log_slow_extra parameter. The explain query says that it's searching 135k rows using where only, and I cannot for the Sep 19, 2019 · After opening a new MYSql connection in the workbench, the very first query takes a very long time (more than 2 mins) to execute. This is a TinyInt field (essentially a boolean 0/1 is stored). Let’s get started! MySQL and your applications. This is O (log n) in the size of the list, whereas an equivalent series of OR clauses is O (n) in the size of the list (i. set global slow_query_log = 1; set global slow_query_log_file = '/var/log/mysql-slow. 5, “The Slow Query Log”. We can easily order and get based on primary key and also there are no joins. The last part of the discussion suggests how you can help the Here we had divided the statement into two parts: 1. id: 1. but if you do the chance is MYSQL needs to use an temporary table and an filesort for the correct results slowing 5. Possible destinations for log entries are log files or the general_log and slow_log tables in the mysql system database. With no argument or an argument of 1, --general_log enables the log. In my experience with SQL Server 2000/2005, large IN clauses for primary key lookups were extremely fast (the database and queries in the application I'm thinking of were all pretty highly optimized; it was all code in a high 5. When you execute queries that take longer than a specified threshold, MySQL treats them as slow queries. SELECT . mysqldumpslow parses MySQL slow query log files and summarizes their contents. e. Jul 24, 2023 · Pt-query-digest processes MySQL query logs and summarizes how database queries are performing, while pt-query-advisor offers recommendations for optimizing slow queries. 0, 5. 51a and by chance I noticed that the same query was running as fast as it should have always done on a server with MySQL 5. Getting query results based on id and order by is only on limited columns we can retrieve data in less time. Enable the MySQL slow query log. #1: Managing the my. Sep 24, 2010 · 1. It's a simple calculation and adds about to nothing to CPU utilization. The prices table have a bit more than 6 million rows and there are indexes on both the product_id column and the Enable query profiling to understand slow query stages. MySQL Server provides flexible control over the destination of output written to the general query log and the slow query log, if those logs are enabled. Version 5. 000 items. You might want to put up information about the database structure (the DDL) and the actual query so people can take a look. You can find instructions on how to do this at: Enabling MySQL slow query logs; Restart MySQL after doing this. The index entries act like pointers to the table rows, allowing the query to quickly determine which rows match a condition in the WHERE clause, and retrieve the other Part of this demo is for basic mysql trouble shooting including use of the slow query log. This table contains a longblob column with an average blob size of 750kb. Keep in mind that the buffer_pool is a "cache". For improved performance, use predicate on the "bare" column, like this, for example: WHERE date_run >= '2014-5-22' AND date_run < '2014-5-29' + INTERVAL 1 DAY. – Bert. 3 Optimizing Subqueries with the EXISTS Strategy. slow_query_log_file = /var/log/mysqld-slow. To specify the initial general query log state explicitly, use --general_log[={0|1}]. This logging functionality comes with MySQL but is turned off by default. 7 fixes this problem with the materialization option. Jan 14, 2015 · Troubleshooting. Recently, (MySQL 5. This topic is covered far and wide on the web, so I'd suggest you look for full-text indexing solution. sql. May 23, 2020 · In the slow query, if we change the ORDER BY from the indexed isbn field to a non-indexed field or leave out the ORDER BY altogether, everything has its normal lightning speed again. Basically this table contains points of interest of an image with respective descriptors. May 22, 2014 · With your query, even with an index available, MySQL is doing a full scan of every single row in the table, each time you run that query. Feb 27, 2021 · df = cx. PROCESSLIST; Check if there is lock blocking your sql: SHOW ENGINE INNODB STATUS. And usually the quick fix is to shrink the buffer_pool. And the query is quite simple, which returns only ~17000 rows. (Note that when we leave out the time portion Nov 14, 2017 · Jan 21, 2011 at 20:06. tables. Beginning with MySQL 5. The script I use insert a simple hash 57. read_sql(conn_url, query, partition_on="ID", partition_num=4) This would split the entire query to four small ones by filtering on the ID column and connectorx will run them in parallel. 2. Let’s say Retrace is reporting a slow page on one of your sites. Feb 27, 2016 · 1. MySQL slow query log The first time I created this query I had used the OFFSET and LIMIT in MySql. 6 (also: Percona and MariaDB versions. The suggested temporary "fix" for the bug is to change your MySQL query (if applicable) to use id > 0 : SELECT COUNT(*) FROM yourtable WHERE id > 0 Jun 4, 2012 · select MAX(id) as id. MYD if it's MyISAM) in your filesystem and see how long that takes. 5 sec. " Set long_query_time to the number of seconds that a query should take to be considered slow, say 0. Here's the query. Often due to a lack of indexes, queries that were extremely fast when a database table had only ten thousand rows will become quite slow when the table has millions of rows. 484 sec / 27. Laptop is still faster yet, extremely slow when compared to 1. Because of this potential for heavy impact, it is important know how to identify and fix those issues. These take at least a second to complete each. To help you understand how performance tuning can boost the performance of your MySQL databases, here are two example case studies: Feb 24, 2017 · I'm having a heckuva time dealing with slow MySQL queries in Python. 2mil rows on MySQL 5. The first query is very slow to run (23 seconds), but removing just one field (Query 2) from the where clause causes the query to run in 0. AND TABLE_NAME LIKE '<TablePrefix>%'; I used this because I wanted to explicitly name the column in the result set. This leads to the roughly two second request mentioned above which has both elements (authentication and database access). The slow query log can either be written to a file on disk, or it can be written to the slow_log table in the mysql database. 4 sec Win7: 9. However, I’ve noticed that it will abort the current query – if you catch it before any output is printed. The issue occurs only for the first query executed after opening the connection. 20 (query takes 24 seconds): MySQL 5. The number of queries that have taken more than long_query_time seconds. 1, “Selecting General Query Log and Slow Query Log Output Destinations”). If you provided the EXPLAIN data and basic DDL, I wouldn't be writing this as the 7. Another solution is trying forcing index. 5 and found it to be extremely slow. Order by on an indexed field should not be slow as it can pull the data in index order. test again on slow_id with a slightly different query (e. To specify the log destination, use the log_output system variable (as described in Section 7. Jun 6, 2010 · The MySQL slow query log contains information about queries that take a long time to execute (see Section 7. If the sub-query is independent of the outer query, then it gets executed once, turned into temporary table internally, then joined to the outer query. (select session_id from entry where created_at > [some timestamp]) Multiple entry's can have the same session ID, but different created_at timestamps. 0 Today I was running into a same kind of problem. conf. 441 sec. To specify a log file name, use --general_log_file= file_name . FROM prices. 000. You can analyse each query using EXPLAIN ORDER BY creation_date DESC) tmp. This will give you far better info about slow queries. To avoid wasted disk space, construct a small set of indexes that . To use it, open the my. This explains the slight performance improvement when using UNION ALL, and also accounts for the performance drop when using UNION instead of two separate queries. But first, you need to narrow the problem down to MySQL. I have a large mysql-table with about 110. WHERE TABLE_SCHEMA = '<DBname>'. I can find tons of stuff about PHP being slow or MySQL being slow, but nothing about PHP+MySQL being extremely slow. You can check out here for more usage and examples. Jan 24, 2016 · I believe MySQL 5. LIMIT 1000. A few notes Jan 21, 2024 · Here is a typical configuration setup that will trigger the slow query log if a query takes longer than 2 seconds, and record that data in the file "/var/log/mysql-slow. 435 seconds to run on the server and 57. Set up indexes on columns used in the WHERE clause, to speed up evaluation, filtering, and the final retrieval of results. The slow query log is output to a file by default. Note If you specify the TABLE log destination, see Log Tables and “ Too many open files ” Errors . Executing the same query in PhpMyAdmin AND Navicat (as a second test) yields a response ~5x faster than in Python. alias) The reason for the third test is that when running the first query MySQL will also load the data in the pool (if using InnoDB, which you don't) and in RAM as well, so that the second query might be faster because pool, memory and any I/O cache have been primed. In Percona Server for MySQL information about the log_slow_rate_limit has been added to the slow query log. cnf file and set the slow_query_log variable to "On. I've tried the following to get queries in the slow query log: Set slow query time to 1 second. The problem is a temporary table and need to sort it before sending the final result to a client. You’ve gone to the trace for that page in Retrace and you can see that it’s definitely a MySQL call that’s underperforming. kd st uq iv uf st kg qt li vc
