Mysql optimize table time estimation I checked with a similar table, then checked the Handler% STATUS values -- Handler_read_first and Handler_read_last incremented by 1 each. This info includes: estimated execution cost, estimated number of returned rows, time to return first Like others pointed out, you need proper indexes. It seems possible to run OPTIMIZE TABLE tblname; without causing any downtime or replication lag. Starting a mysql client with the --auto-rehash option enabled, which is the default. g table i want to optimise is 400mb database storage left is 200mb. No matter the index used, you can't optimize this. Here you may read in more detail about how does it try to do this. Every time I run optimize I can see that InnoDB tables aren't optimized: "Table does not support optimize, doing recreate + analyze instead". Two times already in less than a month I've had my slave become unusable. sql. Will this work or do i need Mysql Innodb Optimize table. I trying to optimize radacct table which grows up to 91628239 rows and growing. Is it possible to optimize all tables with this property in one command in SQL o OPTIMIZE TABLE is essentially useless, especially for ENGINE=InnoDB. After the copy is finished, it will rename, then drop the old table. The MySQL OPTIMIZE table helps you to optimize the table storage space. More discussion here. Addenda. At the simplest level, the "fastest" way to get the table changed is to do it in as few ALTER TABLE statements as possible, preferably one. If your date range is going to be moderate, perhaps a year or two, and assuming your report uses a stored procedure to return the results, you could just create a temporary table on the fly using a rownum technique with limit to get you all of the dates in the range. Plan B: To avoid lengthy locking, chunk the deletes. The table_rows value is an estimation, and you'll get a different number every time even if you OPTIMIZE TABLE is performed online for regular and partitioned InnoDB tables. OPTIMIZE TABLE can be particularly useful for reducing memory usage and improving query performance in cases where a leaf has been online for a Starting a mysql client with the --auto-rehash option enabled, which is the default. The Auto Parallel Load utility facilitates the process of loading data by automating required steps and optimizing the number of parallel load threads. It is a huge table. Learn best practices for using MySQL's OPTIMIZE TABLE command to enhance database efficiency, reclaim space, and boost performance. (Bug #23578) We have a SQL query that is built dynamically, based on which criteria are currently selected. Give it a Try !!! CAVEAT. , so sometimes when I try to run the query (which is frequently run by the admin to make the newsletter, pagination etc) mysql shows this error: too much rows to join, etc. The main recommendation I can make is to use Explain to determine if there is a condition in your where clause that matches against a value (column) that is NOT indexed. Incremental buffers also provide a savings in processing time due to the reduction in copying time. I have a big table on mysql (innodb) which contains products assets (13 millions of rows). optimizing data types and indexes. How can the difference be so extreme, and do I really have to setup a scheduled query, optimizing this table once a week or so? ANALYZE is a special option to instruct the database to also run sql_statement. You need to run OPTIMIZE NO_WRITE_TO_BINLOG TABLE tblname; on master, to avoid writing to the bin logs and replicating the query to the slaves. I've always been using MyISAM tables in my Wordpress blog, however, recently I moved from standard MySQL to Percona Server and started using the InnoDB for tables. `TABLES` WHERE `TABLE_SCHEMA` = I have a database full of time-sensitive data, so on a daily basis I truncate the table and then import the new data (from a merge of other databases) into the truncated table. The OPTIMIZE SQL command takes care of this, using the following syntax: OPTIMIZE TABLE table_name[,table_name] Think of it like defragging your tables. Selecting Maintenance Operations: Analyze, Optimize, Check, etc. Speaking of mysql 8. If you must do it in a Galera cluster (such as PXC), treat it as an ALTER: use TOI (for simplicity) if it is small table; RSU (to avoid blocking) if it is big. Is this something I need to worry about? When I run optimize on it, it tells me that innodb doesn't support optimize and so recreates the table My posts table contains up to 50,000 rows each month, and each row with 3~10kbs of data in avg. (This includes MyISAM indexes, which are BTree-organized. domain = 'system') AND g. I'm interested in creating a recurring event to optimize my database tables every night. Quoting from the Mysql manual : For InnoDB tables, OPTIMIZE TABLE is mapped to ALTER TABLE, which rebuilds the table to update index statistics and free unused space in the clustered index. Tiny tables take less space when living in ibdata1; big/fluctuating tables can be cleaned up if needed via OPTIMIZE if ever needed. MySQL does not support function indexes - Massimog's solution is the only alternative to specifying every possible date range - however since your query is going probably going to extract 1/30th of the rows, using an index lookup will not be significantly faster than using a full table scan. This is a very common and powerful technique. That is why this option is on (optimizer_prune_level=1) by default. I try to count products by download types with the following sql query : MySQL Optimizer: A Comprehensive GuideThe blog provides a deep dive into the MySQL optimizer, crucial for expert DBAs seeking to improve query performance. 3 Optimizer Trace goals “Show details about what goes on in the optimizer” Optimizer trace EXPLAIN ANALYZE Optimization Query SQL Plan Execution There is a lot going on there − rewrites (e. Following is the syntax of the MySQL OPTIMIZE TABLE Title: How to Use the PowerPoint Template Author: The Presentation Company Created Date: 4/30/2018 10:03:51 AM OPTIMIZE TABLE is performed online for regular and partitioned InnoDB tables. If you have deleted most of the rows from a table, OPTIMIZE table needs only enough room to build a new, smaller, copy. Some notes: If there are multiple rows from spc that "match" a row from tsc, the query will return duplicate values of tsc. Running a optimize query for a single table is feasible but not sure how to achieve iterative way of running the query for multiple tables. @T. id along with a count. I am looking for ways to optimize it so that it takes less time to execute. If the table had its own tablespace (built with innodb_file_per_table=ON), then the freed space will be returned to the OS. I am not very sure that this would work and if yes, does it work Skip to main content I'm working on writing a lambda job in node js that runs optimize table query on weekly basis. Modified 8 years, SQL Server Execution Plan Actual Row Count Far Too Large For Simple Select. When i index. The Data_length speaks about how much space a database takes up. Here is the query I write Well, Teradata was implemented before there was Standard SQL, the initial query language was called TEQUEL (TEradata QUEry Language), whose syntax didn't require to list tables within FROM. How can I execute every line via in a MySQL event? I prefer to use the MySQL / MariaDB events and not CREATE INDEX table_number ON table (number); UPDATE Try this - UPDATE inv t1 INNER JOIN inv t2 ON t1. If all your The performance of OPTIMIZE on NDB Cluster tables can be tuned using --ndb-optimization-delay, which controls the length of time to wait between processing batches of rows by OPTIMIZE TABLE. If you need to get down to more fine grained times, query the summary table for full days and the current table for just the record MySQL doesn't "optimize Example difference: count(*): 1876668, table_rows: 1899004. I searched about it and found some posts saying In your scenario, I do not believe that regularly optimizing the table will make an appreciable difference. SELECT, then again with the OPTIMIZE. You can try if it would be faster by forcing MySQL to use an index: from orders as ord force index for join (yourindex) OPTIMIZE TABLE is performed online for regular and partitioned InnoDB tables. MySQL has to scan the entire table, -- hint mysql server about caching SELECT SQL_CACHE sum(foo) FROM bar; MySQL optimizer may be able to Or will MySQL just re-sum the entire table again next time this query is For example, if we index nested loop join two primary key columns and the inner table is smaller than the outer table, we should see that num_rows for the inner index lookup is less than one. Understanding how it works is a critical point in using them effectively. One of the rare cases where OPTIMIZE can be useful is just after deleting lots of rows from a table. Max_heap_table_size is the largest a table can be in the MEMORY storage engine, whether that table is a temp table or non-temp table. g. Is it safe to kill an OPTIMIZE query on an InnoDB table without corrupting the table? The MySQL docs says: However, killing a REPAIR TABLE or OPTIMIZE TABLE operation on a MyISAM table results in a table that is corrupted and is unusable (reads and writes to it fail) until you optimize or repair it again (without interruption). " So it's the same result either way. The OPTIMIZE TABLE statement Learn how to maintain peak MySQL database performance through table optimization techniques, including when and how to optimize. Recode a table in R. The main reason I have used "Explain" on mysql and/or Oracle is to get a sense of how expensive a particular query is and to glean insight into how to optimize the query. optimize table b; optimize table a; Check out more about InnoDB Optimization at: MySQL What I don't understand is why you have created a key for each and every single column of yours, that is a little redundant - as you could just tie in multiple columns as a single key (composite index) - especially if you are only going to compare a single column to another Returning a Table Variable will make it a multi-statement table valued function and can be bad for performance due to the fact that it's treated like a table except there are no statistics available for SQL Server to base a good execution plan on - so it will estimate the function as returning a very small number of rows. LIKE %x% will always require a full table scan. I know that optimize table is supposed to take quite a long time, but it has now been around 10 hours and I'm still waiting for it to finish. Now if I do an "optimize tables" on this table, the query will run in about 0. As my first message here, i don't know if i have to answer or post a new message. Query cost is what optimizer thinks of how long your query will take (relative to total batch time). tuning slow queries. Tmp_table_size is the largest a table can be in memory when it is created automatically by a query. It reorganizes the storage data in a way that increases the Input Output efficiency and reduces the storage space. Here is a fair warning: If you have innodb_file_per_table disbaled, every time you run OPTIMIZE TABLE or ALTER TABLE ENGINE=InnoDB; the ibdata1 file just grows. MySQL doesn't "optimize" count(*) queries in InnoDB because of versioning. The result of the command will be regular EXPLAIN output along with timing and additional information about how the optimizer's expectations matched the actual execution. " This implies that you could turn this feature on, "convert" the existing tables to use a separate InnoDB file with the ALTER TABLE command, Viewed 43 times 0 Should I have enough space for another copy of the table? e. type It's a range condition on g. It is possible that the rows you deleted had very little VARCHAR, TEXT, or BLOB data or even NULL values. 2. Then you have to run OPTIMIZE Manually loading data into HeatWave involves preparing tables on the MySQL DB System and executing load statements. domain and ref on OPTIMIZE TABLE is performed online for regular and partitioned InnoDB tables. (Bug #23578) MySQL OPTIMIZE TABLE Statement. ; Any writes during the optimize will be lost. 1, only if the innodb_file_per_table server system variable is set), Aria, MyISAM and ARCHIVE tables, and should be used if you have deleted a large part of a table or if you have made many changes to a table with variable-length rows (tables that have VARCHAR, VARBINARY, BLOB, or TEXT columns). To execute this statement, you need SELECT and INSERT privileges. Now the innodb data file will not growth too much anymore, and an optimize table will allow you to shrink the involve table data file since now each table will amnage it's own data file. The auto-rehash option causes all InnoDB tables to be opened, and the open table operations cause statistics to be recalculated. Innodb/XtraDB tables do benefit from being reorganized often. Any BTree gets fragmented. Removing the unnecessary JOINs. I have the same problem as here and the one and only given answer doesn't help me (except if the documentation is incorrect). I'd say run that rarely if at all. (Bug #23578) For the time being I've solved the problem by using this approximation: EXPLAIN SELECT COUNT(id) FROM data USE INDEX (PRIMARY) The approximate number of rows can be read from the rows column of the explain plan when using InnoDB as shown above. If, by chance, it doesn't, you should hint or force the multi-column index. It does something different. 1 This is the primary method for optimizing tables in MySQL. The FULL flag is not a valid option for rowstore tables; the syntax is accepted but it will be ignored by SingleStore Helios. Viewed 1k times 1 . You can get data physically laid out in primary key order as well as get a better feel for the primary key and index pages, and so use less space, it’s just that MySQL First of all, this question regards MySQL 3. This SQL has many things that are redundant that may not show up in an explain. For a MyISAM table that uses dynamic row format, updating a row to a longer total I know that optimize table is supposed to take quite a long time, but it has now been around 10 hours and I'm still waiting for it to finish. Why should i run OPTIMIZE on these Table structure optimization has to do with reclaiming unused space after deletions and basically cleaning up the table after structural modifications have been made. Remarks. 2. The table in question stores logs. cc Creating and initialization of Cost_model_server object: ===== The Cost_model_server object OUTPUT: We have two important properties to know whether we should optimize this table or not. 7 to MySQL 8. Also it's possible for other temporary uses of disk space to interfere. I already have an index on table1 for (expire,unreliable,block,deleted,flag,expirationDate). Is having 26 columns ok or mysql optimize tables. load_data DISABLE KEYS; -- load data mysql> ALTER TABLE test You stated the rank is only linked to the image, in which case all you need is table 1 and keep updating the rank in real time. So should you optimize such tables? Maybe! It wouldn't be a bad thing to do it, say once a month. MySQL provides a progress and result table for the optimization process. This article aims to provide a comprehensive guide on how to identify and optimize fragmented MySQL tables to reclaim unused space and improve performance. What is this fragmented table and how does this will impact the functionality and performance. This involves reclaiming unused space resulting from deletes and updates, and coalescing records that have become split and stored non-contiguously. (Bug #23578) If we optimize this table, the size of this file should go down dramatically. optimize table doc. optimize table rebuilds the table for InnoDB so it could take a wicked long time to run. It's used for reclaiming space and recreating indexes. The scope of Slow SQL queries can hinder application performance; learn how to analyze and optimize query execution time effectively. CREATE TABLE definition I would like to optimize the query to reduce the time taken by the Nested Loop and Function Scan. Without knowing the exact data is hard to offer further improvements, but generally you may want to offload MySQL Description: Hi, I reported bug #38049 and this bug report is related and goes further and closer to queries we're using in our product. The first method is to use Optimize table command as shown below. This tutorial explains MySQL OPTIMIZE TABLE statement which defrags tables and recovers unused space. 11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8. I have a simple database table with 170MB overhead. There are a number of suggestions there. It almost never is worth the effort. From the [With selected:] drop-down menu choose Optimize table. The batched_key_access flag controls how the optimizer uses the OPTIMIZE TABLE is performed online for regular and partitioned InnoDB tables. I'd like to OPTIMIZE all currently fragmented tables. Partitioning only works if you will be deleting all rows older than X. cat_name as cat_name, c. view merging) − WHERE analysis, finding ways to read rows (t. It does take time, depending on the size of your table. If it returns a larger number of rows, then therefore the plan generated I am trying to select a number of items from table1 that are not in table2. TABLES WHERE NAME = 'scheme/table_name'; You can monitor the progress whilst the "optimize table" is running, by looking at the size of the temporary file. It's usually in the database data directory, with a temp filename I checked with a similar table, then checked the Handler% STATUS values -- Handler_read_first and Handler_read_last incremented by 1 each. Since OPTIMIZE does not change the contents of the table, just the layout, your questions letting it . If we don't need duplicates, we could return just a distinct list. Instead, you should set a FULLTEXT search for the field - requiring FULLTEXT index and modifying the query to use MATCH AGAINST instead of LIKE. This can be time-consuming depending on the size of the data and indexes. I just explained how OPTIMIZE TABLE works for both storage engines. Over time, especially with frequent insertions and deletions, tables can become fragmented, leading to performance issues. . However, I did have a backup available in case of problems. My MySQL query code likes as shown below, and there are about several thousands of records in the table, by now below SQL executes about 5 minutes and more. InnoDB doesn't support the OPTIMIZE the way MyISAM does. domain = 'queue' OR g. The trick might be to force outputing distinct rows in the Created order at once. What is wrong An index is useful for finding a few rows in a big table, but when you query every row, an index just slows things down. The disadvantage of this approach is that user cant change his vote. During the upgrade of the cluster, the process failed, and according to AWS, they recommended we run Optimize Table on a number of DB tables before proceeding again. pl and similar ones In this process i come across OPTIMIZING fragmented tables. " To enable MySQL optimizer trace, set the optimizer_trace and optimizer_trace_offset variables as shown: mysql> SET SESSION optimizer_trace="enabled=on"; mysql> SET optimizer_trace_offset=-2; Issue the problematic query using EXPLAIN. I recommend you abandon the process rather than trying to speed it up. 11, “Previous NDB Cluster Issues Resolved in NDB Cluster 9. To improve the start up time of the mysql client and to updating statistics, you can turn off auto-rehash using the --disable-auto-rehash option. See Section 2. Sure, InnoDB gets fragmented. ibd is the same size, then it is already defragmented as much as possible. We’ll describe the complete usage of this method with the help of simple examples. Basically, you are doing an OPTIMIZE on the table. It will require extra disk space while it's running, as it creates a copy of the table. It explores key concepts such as the query execution pipeline, optimizer components, cost-based optimization, and indexing strategies. 9. Changes to this variable affect execution of all subsequent queries; to affect one query differently from another, it is necessary to change optimizer_switch before each one. Tested on Mysql 8. The first that comes to my mind is something like this: Now if you know the specific names of the tables you want optimized, you could adjust the query to fetch just those tables. We are using: mysql -- 5. Added two triggers, but as the triggers work with string values and they search for string the database performance might degrade in future when every table will get clean up of unused tables. Data is the same when query is different: SELECT STRAIGHT_JOIN DISTINCT g. Ask Question Asked 8 years, 4 months ago. 2, “Loading Data Manually” . I am worried how this is possible because i don't have any routines in my database and how i can optimize the information_schema because its memory based database and created on the It does take time, depending on the size of your table. ; You are optimizing twice -- once with the CREATE . IF we need to count the number of copies of each tsc,id, we could do that in the query, returning distinct values of tsc. 58, so be advised. Need to reclaim disk space on live server with minimum downtime. Techniques for optimizing joins, subqueries, derived tables, and I have following table structure. I did try changing the eventTime column to an int rather than a datetime but that didn't seem to affect the index use or time. Example difference: count(*): 1876668, table_rows: 1899004. 02 seconds and "Handler_read_next" will have a value of about 1500. ; The Data_free tells the allocated but unused bytes You might save some time by creating the new table, loading the data and then renaming the table. 5 innodb table per file -- on Was a huge table(70% insers/30% deletes -- it means that sometimes we delete rows from this table), this table was dropped with "drop table" command, as we expect, mysql didn't release disk space to OS, but OPTIMIZE TABLE is essentially useless, especially for ENGINE=InnoDB. About 1hr ago I started MySQL optimize on a MyISAM table. I have this MySQL which should be correct syntax: select c. item_ID = table2. Thank you! That's factually not correct, it should not be the answer. The optimizer_prune_level variable tells the optimizer to skip certain plans based on estimates of the number of rows accessed for each table. You will also notice that MySQL will use the multi-column index for the WHERE in the EXPLAIN result. These tables should have information_schema. SELECT NAME, FS_BLOCK_SIZE, FILE_SIZE, ALLOCATED_SIZE FROM INFORMATION_SCHEMA. NB. 1” . h sql/opt_costmodel. (It's not clear why or if we need to return duplicate values. 6) Restore the backup: mylsql -u root -pMyPassword mysql < full. For InnoDB tables, OPTIMIZE is mapped to ALTER TABLE. I deleted just over half of them because disk space was starting to become an issue. When deleting 1/2 a table, an OPTIMIZE after is a A list with all the database's tables will appear. cnf configurations with mysqltuner. I got to SELECT Concat('OPTIMIZE TABLE ', TABLE_NAME, ';') FROM INFORMATION_SCHEMA. The OPTIMIZE TABLE command can be used for both single and multiple tables. I have a large table (FactTable) which inner joins to a small table Hash Match : Incorrect estimation number of rows. OPTIMIZE TABLE does not sort R-tree indexes, such as spatial indexes on POINT columns. But if you're pushing those rows over a slow or already-pegged NIC, to a memory-starved app server, etc. For a single table, the syntax is: It streamlines the process by pre-selecting the table for maintenance, thus saving time and clicks. Do all the RENAMEs in a single RENAME statement to avoid the brief time when no table exists: RENAME TABLE real TO Viewed 950 times 3 . Read the article now! SingleStoreDB is a real-time, distributed SQL database that unifies transactions and analytics in a single engine to drive low-latency access to large datasets, I got the free space (fragmentation issues) in my information_Schema database. When you OPTIMIZE TABLE on InnoDB, the server actually does in fact execute ALTER TABLE ENGINE=InnoDB and ANALYZE TABLE behind the scenes before returning that response so you can indeed run OPTIMIZE TABLE on InnoDB, and Left joins always return a row from the first table, but may return multiple rows if there are multiple matching rows. It had around 17 million records. Defrag using OPTIMIZE TABLE command. name = t2. It is doing essentially what OPTIMIZE does -- copy the table over and rebuild the indexes. That's really an informational message. Tick the tables you wish to optimize, or simply click [Check All] to select all tables. This brings several tables together into one wider table, so in stead of your query joining several tables together, you can just read one table. It basically performs a query against the information_schema database for any table with data_free > 0 and builds a SQL statement to OPTIMIZE only those tables. The block_nested_loop flag of the optimizer_switch system variable controls hash joins. I've got this very simple MySQL query: SELECT target FROM table WHERE goal_id=1 AND year>=2015 AND year<=2020 The above details the cost estimation of all single-table access paths in the MySQL optimizer. What's the easiest way to optimize a MySQL database so that when querying it, the time taken is short? Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company According to MySQL Certification Guide : The OPTIMIZE TABLE statement cleans up a MyISAM table by defragmenting it. The table_rows value is an estimation, and you'll get a different number every time even if you database doesn't change. Otherwise, MySQL locks the table during the time OPTIMIZE TABLE is running. The Mysql index is an important topic. 27, this is displayed in the output of OPTIMIZE TABLE when you run it on an InnoDB table, as shown here: mysql> OPTIMIZE TABLE foo; ALTER TABLE [tbl_name] TYPE=innodb I have just read somewhere that using above alter table statement will optimize an existing table. I have 2 tables with the following definition: Table A: id INT (primary), customer_id INT, offlineid INT Table B: id INT (primary), name VARCHAR(255) Now, table A contains in the range of 65k+ records, while table B contains ~40 records. For more information, see Section 25. Kindly please suggest some steps. 1 INNODB size shrink. The problem here is really that you're selecting 7. Don't use language plpgsql, but turn it into language sql stable then the function isn't a black box to the optimizer any more – user330315. Arguments (Rowstore) The FLUSH flag is not a valid option for rowstore tables. 4” . TABLES WHERE table_schema='database_name';. I have a Person table with huge number of records(for about 16 million), and have a requirement to find all persons, with same lastname, first letter of firstname and birthyear, in other worlds I want to show assuming duplicate persons in UI for users to analyze and decide are there a same person or not. Here a little schema of my database : product <-many2one-- file_item --one2many--> family --many2one--> download_type The *file_item* table is the big table with millions of rows. An estimate of how much Performing multiple updates together is much quicker than doing one at a time if you lock the table. From "High Performance MySQL book" (the percona guys): The usual trick for loading MyISAM table efficiently is to disable keys, load the data and renalbe the keys: mysql> ALTER TABLE test. key_column < 'abc') − Search for query plan *Some* of possible plans are considered − Plan refinement MySQL 5. Question:If we want to do DDL/DML/SELECT fast, without thinking space even if we have fragmentation on table, can we do only analyze table command. 7. 22 – There are lot of questions/answers on this site related to optimize table and analyze table. If your database is receiving a lot of deletes and updates calls, then it might lead to fragmentation in your MySQL data files. If all the required fields are in the same table, it should be the in your first FROM. Right, but I would assert that it happened immediately for you because the table you tested against was very small. Likely, you're doing OPTIMIZE on an InnoDB table (table using the InnoDB storage engine, rather than the MyISAM storage engine). 2, “Switchable Optimizations”). まぁ何のことはなく、show table statusでテーブル一覧を取得し、1つ1つoptimize tableを実行しているだけです。 SHOW TABLE STATUSでテーブルの状態が取得できるので、data_free（開放できるデータ量）が0よりある場合、としていますが、もうちょい大きい値を設 The performance of OPTIMIZE on NDB Cluster tables can be tuned using --ndb-optimization-delay, which controls the length of time to wait between processing batches of rows by OPTIMIZE TABLE. This problem have only started since this table began to grow big. flag_qty = 1; You can create your table with just the duplicates by selecting this data directly into another table instead of doing this flag update first. I need your advice. which is ~20G with 250M rows. Running OPTIMIZE TABLE after deleting such rows won't really make a significant dent in space. Querying it right now can take a few seconds just to find some basic information. The value of the rows field is not merely an estimate depending upon the last time At the point in time when check_interleaving_with_nj() adds the table t5 to the query execution plan, QEP, it also directs the node named NJ2 to mark the table as covered. Maybe some table fluctuates dramatically in size (eg, add a million rows, then delete most of them)? I suggest having innodb_file_per_table ON when creating big or fluctuating tables; OFF for tiny tables. Table 2 just stores unnecessary data. I ended up making the tests on my local by setting up a replication environment. and most of the times its really slow. cat_desc, My goal here was just adding onto an existing query to grab a value from an additional table Optimize MySQL Full outer join for massive amount of data. Just joining on three several-million-row tables shouldn't take much time at all (I'd expect maybe a second or so, just eyeballing your tables and query), provided the tables are properly indexed. If you ran OPTIMIZE TABLE table1; multiple times and the the file table1. cat_id,c. MySQL - How to optimize That is, 99. I’ve been researching how to optimize only fragmented tables in MySQL and reviewed this post on optimizing tables. This is because MySQL copies a table's data to change the schema and making fifteen changes whilst make a single copy is obviously (and really is) faster than `OPTIMIZE TABLE`is a command used in MySQL to reduce fragmentation and optimize the physical structure of the table. This isn't preferable, I know that the best way to optimize is to minimize the number of rows which is possible, but right now I don't have the time to do this. mysql> use thegeekstuff; mysql> OPTIMIZE TABLE EMPLOYEE; The temp table will stay in memory if its size is less than tmp_table_size and less than max_heap_table_size. name AND t1. For this particular query, you can benefit from indexes like: (Location, Date) or (Date, Location) (for the WHERE clause) and (Title, Variables) or (Variables, Title) (for the join condition, ON clause)It would be helpful to know exactly the size (that is, datatype) of the location, Date, Title, and Variables columns, as a Source code for new cost model API and cost module ===== This worklog will implement the following two new classes: Cost_model_server Cost_model_table The implementation of the new code will be in two new source code files named: sql/opt_costmodel. 1. The best practice for OPTIMIZE TABLE on any InnoDB system: do not run it. 9% of the time OPTIMIZE is a waste of time. I helped troubleshoot a site where a query created a very large temporary table, and when four of these queries ran concurrently, the whole disk volume ran out of space. I've got this very simple MySQL query: SELECT target FROM table WHERE goal_id=1 AND year> Simple SQL query but huge table - how to optimize? Ask Question Asked 4 years, Modified 4 years, 9 months ago. How It Works: - Reduces Data Fragmentation: As data is added and deleted, the table can become fragmented You need enough free disk space to store both the original table and the optimized copy at the same time. In this case it is important that we return the expected cost of the operation. It will lock the table while it's running. analyze should be redone whenever the overall distribution of the indexed data changes significantly. This is indicative of An optimize on innodb is effectively just running alter table engine=innodb to rebuild it, reclaiming empty space that is the result of deleting many rows. As you probably understand, the problem is that GROUP BY orders data by UserId, but the resulted set should be ordered by Created; thus, MySQL puts the output in a temporary table, sorts it and outputs. This is what I experienced: Notice a drop in query per second on the slave with my monitoring tool; Connect to the server with the mysql client, run SHOW SET SQL_LOG_BIN=0; OPTIMIZE TABLE tblname; SET SQL_LOG_BIN=1; This will not register the OPTIMIZE TABLE in the You need to think about your requirements a little more carefully. * FROM table1 LEFT JOIN table2 ON table1. The query is good for 2-3 criteria, but will get very slow when selecting more than 5 options (each additional INNER JOIN roughly doubles the execution time) Whenever I try optimize table command, mysql always gives me the following error: 2013 (HY000): Viewed 2k times 0 . This lock is crucial to remember for production environments, as it impacts data availability temporarily. id FROM acl a, groups g WHERE (g. I advise keeping the original normalised tables and building the denormalised table in addition - this way, you're not throwing anything away. It doesn't appear that you are using any fields in any of the joined tables, so remove the joins. OPTIMIZE TABLE works for InnoDB (before MariaDB 10. I've stopped the optimize process a number of times in the past, without adverse effects. Doing optimize table on an InnoDB table is usually not necessary to do frequently, but only after you do a lot of insert/update/delete against the table in a Upon executing the OPTIMIZE TABLE command, MySQL locks the table to a read-only mode until the optimization finishes. (Bug #23578) Plan A: Use a time-series PARTITIONing of the table so that future deletions are 'instantaneous' because of DROP PARTITION. Alert shows that there are 1500% free space in some tables like COLUMNS , ROUTINES. But 5) Start mysql service. "You can make OPTIMIZE TABLE work on other storage engines", but my engine is InnoDB. Beginning with MySQL 5. search_depth from Optimize_table_order controls the exhaustiveness of the The fanout for the outer table is not a good estimate for the final number of rows from the If you ran OPTIMIZE TABLE table1; multiple times and the the file table1. How can I optimize this: SELECT table1. Whenever I try optimize table command, mysql always gives me the following error: 2013 (HY000): Lost connection to MySQL server during query. If you require a field, it shouldn't be in a table that's in a LEFT JOIN - left join is for when data might be in the joined table, not when it has to be. Doing optimize table on an InnoDB table is usually not necessary to do frequently, but only after you do a lot of insert/update/delete against the table in a OPTIMIZE TABLE is performed online for regular and partitioned InnoDB tables. I need to: save the auto mysql optimize tables. If the query is supported by HeatWave, the Extra column in the EXPLAIN output shows the following text: “ Using These estimates are stored in the server_cost and engine_cost tables in the mysql system database and are configurable at any time. This will execute the OPTIMIZE TABLE SQL query on the selected tables and they will be updated and optimized. OPTIMIZE TABLE on innodb does a full re-creation which includes a compact variant of the indexes and it can improve index performance in some border cases by a couple thousand times. I decided cut a oldest part of table and putting it to archive db. Overall, using the OPTIMIZE TABLE statement helps you optimize the storage space of table data and improve the query performance. id SET t1. There are two ways to optimize a table. 16, things might change over time. If you run OPTIMIZE TABLE table_name you get the response "Table does not support optimize, doing recreate + analyze instead. Are there pros and cons I should take into consideration when using OPTIMIZE TABLE? Ditto That has flaws. 0. 1. The intent of these tables is to make it possible to easily adjust the cost estimates that the optimizer uses when it attempts to arrive at query execution plans. 0. because we have 500GB size table and storage engine is innodb it's taking time to optimize table command. That's why I use pt-online-schema-change to run a no-op change (use the --alter=force option), so it can be done any time, without blocking clients. But because you are counting distinct visit rows, left joining to another table while counting distinct visits is the same as just counting the rows of visits. One means of control over optimizer strategies is to set the optimizer_switch system variable (see Section 10. First things first, your second interpretation (B) of the documentation is correct - "if you have deleted a large part of ANY table OR if you have made many changes to a table with variable-length rows. The following example will optimize EMPLOYEE table. Sometimes, MySQL optimizers don’t use the index we want. Our experience shows that this kind of “ educated guess ” rarely misses optimal plans, and may dramatically reduce query compilation times. The sequence of access paths described in the article is based on the enumeration sequence of access paths in the bool JOIN::estimate_rowcount() in the MySQL source code. So here MySQL probably expects to be using the whole [order] table, so it better not use an index. To stop the process, I am in the process of upgrading our AWS Aurora RDS cluster from MySQL 5. There are still many aspects that are not fully explained in this article. The optimizer tries to choose the optimal query plan by looking at your query and statistics of your data, trying several execution plans and selecting the least costly of them. id. Viewed 4k times 1 . A simple RETRIEVE TableName. Or This one. But there are better ways to do the delete, so that is another case to simply avoid. ) Why my mysql table has to optimize frequently. type = a. evaluating my. Todua it doesn't matter. table1 has approximately 3 million rows, and table2 has approximately 8,000. (Bug #23578) Viewed 1k times 4 My user table has over 26 columns, is that normal? The db is already normalized to the 3rd level when this user table caught my eye. See this answer. Now if you know the specific names of the tables you want optimized, you could adjust the query to fetch just those tables. No, you can't speed up the function itself. – When i run optimize table on a innodb table, Viewed 16k times 16 . DATA_FREE &gt; 0. Outside of an Earthquake or Power Outage, running OPTIMIZE TABLE does not harm to the data and indexes get rebuilt. 5 docs about the InnoDB file-per-table mode state "To take advantage of [InnoDB file-per-table] features for an existing table, you can turn on the file-per-table setting and run ALTER TABLE t ENGINE=INNODB on the existing table. Do not use OPTIMIZE TABLE it is (usually) a long wast of time. I then ran optimize table. 23. , the slowness could have nothing to do with your query at all, I/ Introduction. Syntax. I ran this query and it identified 148 tables for optimization. MySQL table data physical fragmentation. But doesn't it lock the table and block queries while you optimize? Yes, sort of. 3 million records. This is indicative of optimizing MIN and MAX. 6. Currently I am running OPTIMIZE on the table after I have imported the daily refresh of data. When using MyISAM this will remain EMPTY as the table reference isbeing optimized away- so if I tried a join back to the table, which keeps the 'Using index' but takes around 20 seconds. item_ID WHERE Starting a mysql client with the --auto-rehash option enabled, which is the default. id <> t2. I've been DELIMITER // CREATE PROCEDURE util_optimize_all_tables() SQL SECURITY INVOKER BEGIN DECLARE endloop INT DEFAULT 0; DECLARE tableName CHAR(100); DECLARE rCursor CURSOR FOR SELECT `TABLE_NAME` FROM `information_schema`. ColumnName carried enough information for the Parser/Optimizer to resolve tablename and columnname. wcuk dvs hsfnh blgif kxit pel lzbe qsbb dtml toa