Mysql optimize table. Identify Tables for Optimization.

This process can be a lot faster, especially for large indexes which would get inserts in very random order Sep 20, 2021 · Before we upgrade from version 5. You can use this statement to verify that the contents are the same before and after a backup, rollback, or other operation that is intended to put the data back to a known state. In this step, you’ll run the same query you ran in Step 3 one more time to check how query cache has optimized the performance of your MySQL server. 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. Depending on your job role (developer, DBA, or a combination of both), you might optimize at the level of individual SQL statements, entire applications ANALYZE TABLE with the DROP HISTOGRAM clause removes histogram statistics for the named table columns from the data dictionary. On the CREATE INDEX statement, use the clause USING BTREE or USING HASH. innodb. 6. MySQL. Using OPTIMIZE TABLE defragments InnoDB tables, which might reduce the size, especially right after major data changes like bulk deletes. In your role as a database designer, look for the most efficient way to organize your schemas, tables, and columns. In order to use it to update fulltext index statistics, the innodb_optimize_fulltext_only system variable must be set to 1. edited Aug 12, 2017 at 10:23. I'm having issues with a database that is getting quite slow. Note that I'm using barracuda format and file-per-table. Are there pros and cons I should take 9. B-tree indexes are fast for queries that do greater-than or less-than comparisons through May 12, 2010 · 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. Nov 13, 2023 · Command: In MySQL’s InnoDB storage engine, the OPTIMIZE TABLE command can be used to reorganize a table and its associated indexes. For cases when a derived table requires materialization, the optimizer may add an index to the materialized table to speed up access to it. Impact:Performance: Reorganizing is generally less resource 10. Queries, in the form of SELECT statements, perform all the lookup operations in the database. I am not very sure that this would work and if yes, does it work even if table type is already InnoDB? mysql. Oct 5, 2010 · 10. Is there a way (built-in command or common stored procedure) to run this optimization for every table in the database and/or server install, or is this something you'd have to script up yourself? Ever. After the DB upgrade to 5. Is there anyother way I could use in order to reduce the table size? Ps: Engine Is InnoDB. Performance is not the reason to use OPTIMIZE TABLE. InnoDB has been the default storage engine since 2010. 2GB and the optimize table script for this table has consume 45 mins . 18, “CREATE TABLE Statement”. Dec 11, 2023 · MySQL でテーブルを最適化するタイミングと理由. 4 MyISAM Table Optimization. 5 Optimizing Database Privileges. See full list on phoenixnap. The table in question stores logs. Chapter 8 Optimization. If the data is huge, remove the PXC node from the cluster, run OPTIMIZE TABLE at will, and add the PXC back into Feb 23, 2013 · First of all, I am new to optimizing mysql. This statement is not supported for views. An ORDER BY with and without LIMIT may return rows in different orders, as discussed in Section You can use OPTIMIZE. The third statement removes the histogram for c2 , leaving those for c1 and c3 unaffected. Connect to your MySQL database, and execute the following query, which will display how much unused space are available in every table. 9. 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. mytable; Look at two scenarios involving innodb_file_per_table and this OPTIMIZE TABLE. mytable, you enter this command: OPTIMIZE TABLE mydb. Although it is not always reproducible, but possibly related: If the optimization processes t1 first and the WHERE clause produces an empty result, the join must necessarily be empty and the derived table need not be materialized. My configuration was: max_heap_table_size = 16M tmp_table_size = 32M The result: temp table to disk percent + - 12. In fact, the example I have can be performed manually as shown. Aug 9, 2022 · Description: Using OPTIMIZE TABLE on any InnoDB table returns a note that the table does not support optimize, yet it also returns a status of OK. 9. Dec 9, 2010 · Why you shouldn’t necessarily optimize tables with MySQL OPTIMIZE. 6. But in practice, it won't improve performance in a significant way. 業務の役割 (開発者、データベース管理者、また Oct 25, 2006 · Description: After upgrading our database server from MySQL 3. In my company we have tables about 2-3 gb. Jul 4, 2014 · 1. 27, this is displayed in the output of OPTIMIZE TABLE when you run it on an InnoDB table, as shown here: Apr 25, 2024 · This article explained different methods for improving MySQL performance and tuning your database. 1 WHERE Clause Optimization. 17, requires that you have the FILE privilege. Dec 13, 2017 · The filtering is being used to determine whether a specific row from the right (nullable) table should be matched up or not. column1 VARCHAR(5) NOT NULL, Mar 29, 2011 · MySQL has an OPTIMIZE TABLE command which can be used to reclaim unused space in a MySQL install. May 24, 2023 · Table optimization, in the context of MySQL, refers to the process of managing data storage effectively and enhancing the speed of data retrieval operations. PostgreSQLでは「vacuum」とSQLクエリに投げるだけで全テーブル最適化してくれたのですが、OPTIMIZE TABLEの場合はひとつひとつテーブル名を指定しなければならないのでPHPで作りました。. This statement requires SELECT and INSERT privileges for the table. See Section 17. 예제 코드: mysql>SELECTTABLE_NAME, data_length, data_free->FROM information_schema. 33 , the entire optimization script can complete within 1. Apr 27, 2012 · Optimize Table Taking Forever. This section explains how to optimize database operations for InnoDB tables. Let’s get started! MySQL and your applications. It also has a very positive affect on query performance, reducing the select query response time from 0. ANALYZE TABLE works with InnoDB, NDB, and MyISAM tables. This section describes when MySQL can use an index to satisfy an ORDER BY clause, the filesort operation used when an index cannot be used, and execution plan information available from the optimizer about ORDER BY . この記事はMySQL Advent Calendar 2019の25日目の記事です。. OPTIMIZE TABLE does a table repair and a key analysis, and also sorts We would like to show you a description here but the site won’t allow us. 6 Other Optimization Tips. If you’re running Innodb Plugin on Percona Server with XtraDB you get the benefit of a great new feature – ability to build indexes by sort instead of via insertion. The most general way to satisfy a GROUP BY clause is to scan the whole table and create a new temporary table where all rows from each group are consecutive, and then use this temporary table to discover groups and apply aggregate functions (if any). I ran this query and it identified 148 tables for optimization. By optimizing tables, one can make sure that the database server uses less disk space, processes queries more efficiently, and retrieves data faster. 0 8. Since fulltext re-organization can take a long time All of the following tables are used as constant tables: SELECT * FROM t WHERE primary_key=1; SELECT * FROM t1,t2 WHERE t1. Method #5: Repair During Server Startup. Is it not possible to optimize without recreate in this I have a table with 707 GB in my database, I tried the command "optimize table mytable" but unfortunatelly it seems not work because my table keep the size 707 GB. It had around 17 million records. Look for bottlenecks (hardware and software), queries that are doing more work than needed, and consider using automated tools and the EXPLAIN function to evaluate your database. If you want to have a tool that repairs tables by default, you should just make a copy of mysqlcheck named mysqlrepair, or make a symbolic link to mysqlcheck named mysqlrepair. 7. Feb 1, 2010 · 10. 6, “Limits on Table Size” . This will analyze the table and make changes to improve performance. I have no experience with MySQL, but your issue may not be platform specific. Feb 21, 2024 · You can execute this command through any MySQL client. 33. MyISAM tables are used as the exception rather than the preferred choice for storage engine. tables->WHERE table Oct 21, 2011 · To optimize the table will help to reduce the size (index will be recalculated etc. 2. Once your data reaches a stable size, or a growing table has increased by tens or some hundreds of megabytes, consider using the OPTIMIZE TABLE statement to reorganize the table and compact any wasted space. This statement requires the SELECT privilege for the table. The positive side is that the . The first – and most skipped! – performance upgrade every user of MySQL should do is tweak the configuration. Apr 25, 2016 · This tutorial explains how to optimize MySQL to defrag tables and reclaim unused space. Failures can happen more with 5. This article covers various methods, such as OPTIMIZE TABLE command, mysqlcheck tool, and GUI tool dbForge Studio for MySQL. . After extensive changes to a table, this statement may also improve performance of statements that use the table, sometimes significantly. This will leave the space previously occupied to add further to the Aug 16, 2011 · Internally, OPTIMIZE TABLE perform several operations (copying data to a temp file, recreate indexes, recompute index statistics). These software constructs result in CPU and I/O operations at the hardware level, which you must minimize and make as efficient as possible. Jun 30, 2022 · Fixing Slow Queries. 2 Optimizing SQL Statements. Example Code: -- Syntax: Use your_database_name; mysql> USE test; Once connected with the desired database, use the following query to get the table’s status. OPTIMIZE TABLE does a table repair and a key analysis, and also sorts OPTIMIZE TABLE works if the table is created in a separate tablespace, according to the Amazon RDS default innodb_file_per_table configuration setting. InnoDB is the default storage engine in MySQL. Oct 30, 2017 · Configuration Optimization. Its value is a set of flags, each of which has a value of on or off to indicate whether the corresponding optimizer behavior is enabled or disabled. ) If you deleted half of the rows, you should optmize your table. #4 and #5: Indexes and partitions. Example: If you optimize mydb. Identify Tables for Optimization. e. #2 and #3: Check up on MySQL storage engines and schema design. Check all MySQL tables at once. 4. 63 to 0. This statement generally works only with MyISAM, BDB Jun 4, 2015 · The message you are getting is basically MySQL server repeating what the InnoDB storage engine told MySQL server: Table does not support optimize is the InnoDB storage engine saying "I (the InnoDB storage engine) don't do an OPTIMIZE operation like my friend (the MyISAM storage engine) does. By default, an OPTIMIZE TABLE will defragment a table. According to MySQL Certification Guide : The OPTIMIZE TABLE statement cleans up a MyISAM table by defragmenting it. 第 8 章 最適化. MySQL will pick one of the tables to start with, then reach into the other one for the other columns needed. Beginning with MySQL 5. To coalesce fragmented rows and eliminate wasted space that results from deleting or updating rows, run myisamchk in recovery mode: $> myisamchk -r tbl_name. " So I'm guessing there will be some performance gain, even if the storage medium is SSD (as the linked list of To optimize the table, issue the following command, where "mytablename" is the name of the MySQL table to optimise: After doing this (it may take a few seconds dpending on the size of the table, free space etc) and running "show table status" again, the result should look much better: Name: tblmailqueue. The reorganized tables require less disk I/O to perform full table scans. However, ALTER TABLE ignores DATA. The core logic of a database application is performed The default behavior of checking tables ( --check) can be changed by renaming the binary. The effective maximum table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits. primary_key=t1. When doing bulk inserts into tables with auto-increment columns, set innodb_autoinc_lock_mode to 2 (interleaved) instead of 1 (consecutive). Running OPTIMIZE TABLE will cause all the data and index pages for mydb. 最適化には、いくつかのレベルでの構成、チューニング、およびパフォーマンスの測定が含まれます。. Optimization involves configuring, tuning, and measuring performance, at several levels. MySQL provides optimizer control through system variables that affect how query plans are evaluated, switchable optimizations, optimizer and index hints, and the optimizer cost model. Optimization is useful when many rows have been deleted from a table. 本エントリでは下記の2点をランダム Feb 15, 2024 · First, we should analyze the tables that we want to optimize. 여러 테이블을 최적화하려면 다음 쿼리를 사용하십시오. If the table had its own tablespace (built with innodb_file_per_table=ON), then the freed space will be returned to the OS. 4 current 5. The table rebuild triggered by OPTIMIZE. ALTER TABLE permits them only as partitioning options, and, as of MySQL 5. Analyze table performs a key distribution analysis and stores the distribution for the named table or tables. 0 Reference Manual / / / / / WHERE Clause Optimization. This section discusses optimizations that can be made for processing WHERE clauses. id; The best join combination for joining the tables is found by trying all possibilities. 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 Dec 24, 2019 · MySQL InnoDBの領域最適化. Aug 12, 2017 · 1. For descriptions of all table options, see Section 13. 3 Optimizing for Many Tables. Optmize doesn't take so much like delete. primary_key=1 AND t2. The fact is that I have in my web application (around 400 queries per second), a query that uses a GROUP BY that i can´t avoid and that is the cause of creating temporary tables. cnf file. Following is the syntax of the MySQL OPTIMIZE TABLE Apr 5, 2011 · hugeCrossingTable: INDEX(field1, field3, field2) otherTable: INDEX(field2, field1, field3) and drop the current KEY field1 ( field1) as being redundant. The guidelines cover SQL operations that read and Dec 16, 2018 · OPTIMIZE TABELを全テーブルに実行. In some cases, MySQL is able to do much better than that and 10. 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. You can use OPTIMIZE TABLE to reclaim the unused space and to defragment the data file. The tuning guidelines in this section help to speed up all kinds of MySQL applications. the mysql query cache was turned off to demonstrate. So, it's supposed to hit the index and run almost instantly, and it did when the testing started, but now, after millions of rows were removed, it gets stuck in the 'optimizing' state for several minutes. MySQLのInnoDBの領域最適化について最近確認し直したことをまとめたいと思います. alter. The analyzer in phpMyAdmin recommends that I run OPTIMIZE TABLE on my tables. 6, “AUTO_INCREMENT Handling in InnoDB” for details. 5 hours. OPTIMIZE TABLE does a table repair and a key analysis, and also sorts You can use OPTIMIZE TABLE to reclaim the unused space and to defragment the data file. 0 latest as well. この章では、MySQL のパフォーマンスを最適化する方法について説明し、例を示します。. Jun 3, 2024 · It’s a command-line utility that can check, repair, and optimize all database tables. But before doing so, I would (of course) like to know if there is anything that can happen to the data in the tables, or if this operation is entirely harmless. When performing bulk inserts, it is faster to insert rows in Feb 14, 2020 · Note that the dowhile() procedure is ongoing or can be ran for a short while then execute the insert on T2 even if it is continuously failing with Duplicate entry. Syntax. The innodb_ft_num_word_optimize option defines the number of words that are optimized each time OPTIMIZE TABLE is run. An exclusive table lock is only taken briefly during the prepare phase and the commit phase of the operation. Database performance depends on several factors at the database level, such as tables, queries, and configuration settings. まぁ何のことはなく、SHOW TABLE STATUSで CHECKSUM TABLE reports a checksum for the contents of a table. 10. ibd file for the table is reduced after an optimize table. The script To avoid lengthy rebuild times for full-text indexes on large tables, you can use the innodb_ft_num_word_optimize option to perform the optimization in stages. MySQL will create a copy of your table on disk. TABLE to reclaim the unused space and to defragment the data file. 17以下ではOPTIMIZE TABLEが更新ステートメントをブロックしてしまうため、 本番環境で使っているMySQLにOPTIMIZE TABLEを行う場合には時間的な余裕を持って行うか、 mysqldumpを使ってdumpしたSQLを使用して別テーブルとして用意したのちにRENAME TABLEをするなど MySQL dynamically optimize innodb tables without "file per table" setting. Aug 27, 2013 · Optimizing this table is going to take a lot of time. 11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8. Depending on your job role (developer, DBA, or a combination of both), you might optimize at the level of individual SQL statements, entire applications Nov 2, 2023 · Learn how to identify and optimize fragmented MySQL tables to reclaim unused space and improve performance. OPTIMIZE TABLE uses online DDL for regular and partitioned InnoDB tables, which reduces downtime for concurrent DML operations. , VARCHAR , BLOB, and TEXT columns). Some techniques for keeping individual queries fast involve splitting data across many tables. I’ve been researching how to optimize only fragmented tables in MySQL and reviewed this post on optimizing tables. @Michael-sqlbot As shown in my answer, I ran OPTIMIZE TABLE dat; in MySQL 5. For best performance with MEMORY tables, examine the kinds of queries against each table, and specify the type to use for each associated index, either a B-tree index or a hash index. 2 Disadvantages of Creating Many Tables in the Same Database. 29 and it complained immediately, Table does not support optimize, doing recreate + analyze instead. その結果、未使用のスペースが発生し Jun 6, 2023 · Conclusion – MySQL Optimize Table. mytable; SUGGESTION. optimization. Tuning these statements is a top priority, whether to achieve sub-second response times for dynamic web pages, or to chop hours off the time to generate huge overnight reports. Only one table name is permitted for this syntax. N. We can optimize multiple tables simultaneously by specifying their names in a comma-separated list within the same Feb 14, 2020 · As per MySQL Documentation, OPTIMIZE TABLE and ANALYZE TABLE. 3. com 10. The examples use SELECT statements, but the same optimizations apply for WHERE clauses in DELETE and UPDATE statements. See Section 10. TABLEAS SELECT , INSERT. One means of control over optimizer strategies is to set the optimizer_switch system variable (see Section 10. That's why I recommend ALTER TABLE dat ENGINE=InnoDB; ANALYZE TABLE dat;. 예제 코드: mysql> OPTIMIZETABLE tableName1, tableName2; 이제 다음 명령을 사용하여 원하는 테이블이 최적화되었는지 확인합니다. 9, we are experiencing severe problems with the OPTIMIZE TABLE command which results in corrupted tables or the loss of all data in the affected table. It's also useful to run this statement periodically with a table that contains several variable-character-width columns (i. OPTIMIZE TABLE works for InnoDB , MyISAM, and ARCHIVE tables. 3 Optimization and Indexes. The core logic of a database application is performed through SQL statements, whether issued directly through an interpreter or submitted behind the scenes through an API. 1 Optimizing Storage Layout for InnoDB Tables. To execute this statement, you need SELECT and INSERT privileges. You can optimize a table in the same way by using the OPTIMIZE TABLE SQL statement. 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. Dec 29, 2022 · In this article, we’ll walk through five ways to quickly improve your MySQL database performance. You can also define the columns and constraints and insert data to the new table like so: CREATE TABLE new_table (. First, connect to your MySQL server as the root user: sudo mysql -u root -p. Chapter 10 Optimization. Depending on the size of your innodb_buffer_pool (if the table is innodb), free memory on the host, I would try to preload the whole table in the page cache of the OS, so that at least reading the data will be sped up by a couple orders of Oct 12, 2015 · OPTIMIZE NO_WRITE_TO_BINLOG TABLE mydb. " 9. As a dry run I ran the same command (optimize table) on a smaller table in the same DB and mysql insists on a recreate+analyze instead. The OPTIMIZE TABLE script have to run for 4 hour. 5 Optimizing for InnoDB Tables. If you invoke mysqlrepair, it repairs tables. 16 ORDER BY Optimization. To optimize a table, you can use the OPTIMIZE TABLE command. MySQL 8. 5. 1 Optimizing SELECT Statements. 4” . I deleted just over half of them because disk space was starting to become an issue. 23. I'm running mysql 5. 2 Switchable Optimizations. This is intended to be a temporary setting, and should be reset to 0 once the fulltext index has been re-organized. How to optimize InnoDB tables in MySQL. 1. mytable to be appended contiguously to ibdata1. For more information, see the MySQL documentation for File-per-table tablespaces . 3 Optimizing INFORMATION_SCHEMA Queries. It reorganizes the storage data in a way that increases the Input Output efficiency and reduces the storage space. 17 GROUP BY Optimization. 本エントリの内容. If you want that your queries will be faster, optimize your table. The MySQL OPTIMIZE table helps you to optimize the table storage space. 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. Engine: MyISAM. Improving database performance in general. For example: OPTIMIZETABLE your_table_name; Simply replace your_table_name with the actual name of the table you want to optimize. We can use the OPTIMIZE TABLE command provided in MySQL to defragment the data used for storing the fragmented table content because of heavy INSERT, UPDATE, and DELETE operations on the table. 6 and I am trying to optimize a large table without mysql recreating it. – Aug 9, 2022 · 1. The manual says about "optimize table": "Deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions. 7 (the current version) has much better defaults Feb 2, 2017 · If you have deleted most of the rows from a table, OPTIMIZE table needs only enough room to build a new, smaller, copy. This chapter explains how to optimize MySQL performance and provides examples. 39 seconds. Optimize table reorganizes the physical storage of table data and associated index data, to reduce storage space and improve I/O efficiency when accessing the table. The first step is to identify whether you have fragmentation on your MySQL database. アプリケーションがデータベースに対して多くの DELETE および UPDATE 操作を実行している場合、MySQL のデータファイルが断片化される可能性が高くなります。. After the copy is finished, it will rename, then drop the old table. When we drill down further to each table , there are 1 table with 5. We must be connected to our database using the following command. 6 to 5. 3 Optimizer Hints. As you work on database performance, you start by Feb 1, 2010 · 10. # mysqlcheck -u username -p --auto-repair --check --optimize database_name. 4 Optimizing Database Structure. 2, “Switchable Optimizations” ). In the WHERE clause, you have to allow for the values from the table on the right to be NULL (or else you'll effectively change the LEFT JOIN into an INNER JOIN). 1. B. #1: Managing the my. Example Code: This tip is valid for inserts into any table, not just InnoDB tables. 9 Controlling the Query Optimizer. The second statement updates the histograms for c1 and c3, leaving the c2 histogram unaffected. The server maintains histogram statistics about column values in the column_statistics data dictionary table (see Section 10 MySQL OPTIMIZE TABLE Statement. InnoDB is the storage engine that MySQL customers typically use in production databases where reliability and concurrency are important. This variable has global and session values and can be changed at runtime. 2 Optimizing Subqueries, Derived Tables, and View References. If your MySQL database runs slowly, you can do a few things to speed it up — like optimizing your tables. But TABLE to reclaim the unused space and to defragment the data file. If T2 loop is cancelled the optimize table (T3) will not fail in succeeding loops. Apr 28, 2015 · The explain command on this query shows: '1', 'SIMPLE', NULL, NULL, NULL, NULL, NULL, NULL, NULL, 'Select tables optimized away'. To optimize several tables simultaneously, list them separated by commas: OPTIMIZETABLE table_name1, table_name2, table_name3; Dec 20, 2016 · 5. mytable; Note that mysql performs something the following under the Jun 12, 2019 · Step 5 — Testing Your MySQL Server with Query Cache Enabled. I have just read somewhere that using above alter table statement will optimize an existing table. 4 Optimizing Data Change Statements. Even if you use optimize table to free the space used from deleted records, it will reuse it later. 3. 1 How MySQL Opens and Closes Tables. Run the one of the above OPTIMIZE TABLE scenarios on one PXC node at a time while redirecting reads and writes from the cluster. May 22, 2023 · CREATE TABLE new_table [AS] SELECT [columns] FROM old_table; MySQL will recreate all columns, data types and data from the old_table. ANALYZE TABLE t DROP HISTOGRAM ON c2; The first statement updates the histograms for columns c1, c2, and c3, replacing any existing histograms for those columns. Apr 24, 2017 · 16. Next, check out our guide on how to optimize MySQL tables. As when tuning application code, you minimize I/O, keep related items together, and plan ahead so that performance stays high as the data volume increases. When the number of tables runs into the thousands or even millions, the overhead of dealing with all 10. 7 but still can be reproduced in 8. Note. 5. This process can help improve performance by reorganizing how data is stored and accessed. mytable; METHOD #3 OPTIMIZE LOCAL TABLE mydb. ALTER TABLE [tbl_name] TYPE=innodb. SCENARIO #1 : innodb_file_per_table disabled. Jun 20, 2009 · Based on this article on Table Optimization. 8. Both of those are "composite" and "covering". Replace username with your MySQL username and database_name with your database name. 5% OPTIMIZE TABLE mydb. The optimizer_switch system variable enables control over optimizer behavior. OPTIMIZE TABLE works for InnoDB , MyISAM, and Use this statement to optimize the data contained in a table. This seems to contradict itself. Another hint for deleting many many rows from You can use OPTIMIZE. This has the effect of defragmenting the table and reducing the size of the table on disk down to 105MB. 52 to 4. DIRECTORY and INDEX DIRECTORY when given as table options. TABLE is completed in place. An alternative is to configure the server to use innodb_file_per_table, but this will require a backup, drop database and restore. Last updated at 2019-12-26Posted at 2019-12-24. 2. This involves reclaiming unused space resulting from deletes and updates, and coalescing records that have become split and stored non-contiguously. 1 Optimization Overview. For more information, see Section 25. bg wl oq yc ke vy ih gm an ay