Home > Articles

This chapter is from the book

This chapter is from the book

3.5 Checking Tables with mysqlcheck and myisamchk

The mysqlcheck and myisamchk programs are used to check and repair tables (primarily MyISAM tables). They can help you keep your tables free from problems, or repair them if problems do occur—for example, if a MyISAM table becomes damaged as the result of a server crash.

mysqlcheck and myisamchk are similar in purpose, but they do have some differences. Here's a comparison of the two programs:

Both programs can check, repair, and analyze MyISAM tables. mysqlcheck also can optimize MyISAM tables, as well as check InnoDB tables and analyze BDB tables. There are certain operations that myisamchk can perform that mysqlcheck cannot, such as disabling or enabling indexes, although these operations aren't discussed in this study guide.

The two programs differ significantly in their mode of operation. mysqlcheck is a client program that communicates with the MySQL server over a network connection. It provides a command-line interface to the table-maintenance SQL statements supported by the server, such as CHECK TABLE and REPAIR TABLE. mysqlcheck determines which options were given on the command line, and then sends appropriate SQL statements to the MySQL server to perform the requested operation. This means that mysqlcheck requires the server to be running. It also means that you can use mysqlcheck to connect to remote servers. In contrast, myisamchk isn't a client program. It's a utility that operates directly on the files that represent MyISAM tables. This means that you must run myisamchk on the server host where those files are located. In addition, you need filesystem read privileges on those files for table checking operations, and write privileges for table repair operations.

The two programs also differ in their relationship with the server while they're running. With mysqlcheck, there's no problem of interaction with the server because mysqlcheck asks the server itself to do the work of checking and repairing the tables. With myisamchk, you need to make sure that the server doesn't have the tables open and isn't using them at the same time. It's possible to get incorrect results or even to cause table damage if table files are used by myisamchk and the server simultaneously. The most certain way to avoid conflict is to bring the server down while running myisamchk. It's also possible to lock the tables while checking or repairing them with myisamchk, but the procedure is not described here. You can find the details in the MySQL Reference Manual.

The rest of this section describes how to use mysqlcheck and myisamchk.

mysqlcheck has three general modes of operation, depending on how it is invoked:

  • By default, mysqlcheck interprets its first nonoption argument as a database name and checks all the tables in that database. If any other arguments follow the database name, mysqlcheck treats them as table names and checks just those tables. For example, the first of the following commands checks all the tables in the world database; the second checks just the City and Country tables in that database:

  • shell> mysqlcheck world
    shell> mysqlcheck world City Country
  • With the --databases (or -B) option, mysqlcheck interprets its nonoption arguments as database names and checks all the tables in each of the named databases. The following command checks the tables in both the world and test databases:

  • shell> mysqlcheck --databases world test
  • With the --all-databases (or -A) option, mysqlcheck checks all tables in all databases:

  • shell> mysqlcheck --all-databases

The procedure for using myisamchk is quite different, due to the need to avoid using tables at the same time the server might be accessing them. Use myisamchk as follows:

  1. Stop the server so that it cannot access the tables while you're working with them.

  2. From a command prompt, change location into the database directory where the tables are located. This will be the subdirectory of the server's data directory that has the same name as the database containing the tables you would like to check. (The reason for changing location is to make it easier to refer to the table files. You can skip this step if you like, but you'll have to specify to myisamchk the directory where the tables are located.)

  3. Invoke myisamchk with options indicating the operation you want performed, followed by arguments that name the tables on which myisamchk should operate. Each of these arguments can be either a table name or the name of the table's index file. An index filename is the same as the table name, plus an .MYI suffix.

The default myisamchk operation is to check tables. If that's what you want to do, no options are necessary and you need only name the table or tables to be checked. For example, to check a table named City, either of these commands will do:

shell> myisamchk City
shell> myisamchk City.MYI

To repair a table, use the --recover option:

shell> myisamchk --recover City

mysqlcheck and myisamchk both take many options to control the type of table maintenance operation performed. The following list summarizes some of the more commonly used options. For the most part, the list contains options that are understood by both programs. Where this isn't the case, it's noted in the relevant option description.

  • --analyze or -a
  • Analyze the distribution of key values in the table. This can improve performance of queries by speeding up index-based lookups.

  • --auto-repair (mysqlcheck only)
  • Repair tables automatically if a check operation discovers problems.

  • --check or -c
  • Check tables for problems. This is the default action if no other operation is specified.

  • --check-only-changed or -C
  • Skip table checking except for tables that have been changed since they were last checked or tables that haven't been properly closed. The latter condition might occur if the server crashes while a table is open.

  • --fast or -F
  • Skip table checking except for tables that haven't been properly closed.

  • --extended (for mysqlcheck), --extend-check (for myisamchk), or -e (for 
          both programs)
  • Run an extended table check. For mysqlcheck, when this option is given in conjunction with a repair option, a more thorough repair is performed than when the repair option is given alone. That is, the repair operation performed by mysqlcheck --repair --extended is more thorough than the operation performed by mysqlcheck --repair.

  • --medium-check or -m
  • Run a medium table check.

  • --quick or -q
  • For mysqlcheck, --quick without a repair option causes only the index file to be checked, leaving the datafile alone. For both programs, --quick in conjunction with a repair option causes the program to repair only the index file, leaving the datafile alone.

  • --repair (for mysqlcheck), --recover (for myisamchk), or -r (for both programs)
  • Run a table repair operation.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020