pt-archiver

NAME

pt-archiver - Archive rows from a MySQL table into another table or a file.

SYNOPSIS

Usage

pt-archiver [OPTIONS] --source DSN --where WHERE

pt-archiver nibbles records from a MySQL table. The –source and –dest arguments use DSN syntax; if COPY is yes, –dest defaults to the key’s value from –source.

Examples

Archive all rows from oltp_server to olap_server and to a file:

pt-archiver --source h=oltp_server,D=test,t=tbl --dest h=olap_server \
  --file '/var/log/archive/%Y-%m-%d-%D.%t'                           \
  --where "1=1" --limit 1000 --commit-each

Purge (delete) orphan rows from child table:

pt-archiver --source h=host,D=db,t=child --purge \
  --where 'NOT EXISTS(SELECT * FROM parent WHERE col=child.col)'

RISKS

Percona Toolkit is mature, proven in the real world, and well tested, but all database tools can pose a risk to the system and the database server. Before using this tool, please:

  • Read the tool’s documentation
  • Review the tool’s known “BUGS”
  • Test the tool on a non-production server
  • Backup your production server and verify the backups

DESCRIPTION

pt-archiver is the tool I use to archive tables as described in http://tinyurl.com/mysql-archiving. The goal is a low-impact, forward-only job to nibble old data out of the table without impacting OLTP queries much. You can insert the data into another table, which need not be on the same server. You can also write it to a file in a format suitable for LOAD DATA INFILE. Or you can do neither, in which case it’s just an incremental DELETE.

pt-archiver is extensible via a plugin mechanism. You can inject your own code to add advanced archiving logic that could be useful for archiving dependent data, applying complex business rules, or building a data warehouse during the archiving process.

You need to choose values carefully for some options. The most important are --limit, --retries, and --txn-size.

The strategy is to find the first row(s), then scan some index forward-only to find more rows efficiently. Each subsequent query should not scan the entire table; it should seek into the index, then scan until it finds more archivable rows. Specifying the index with the ‘i’ part of the --source argument can be crucial for this; use --dry-run to examine the generated queries and be sure to EXPLAIN them to see if they are efficient (most of the time you probably want to scan the PRIMARY key, which is the default). Even better, examine the difference in the Handler status counters before and after running the query, and make sure it is not scanning the whole table every query.

You can disable the seek-then-scan optimizations partially or wholly with --no-ascend and --ascend-first. Sometimes this may be more efficient for multi-column keys. Be aware that pt-archiver is built to start at the beginning of the index it chooses and scan it forward-only. This might result in long table scans if you’re trying to nibble from the end of the table by an index other than the one it prefers. See --source and read the documentation on the i part if this applies to you.

Percona XtraDB Cluster

pt-archiver works with Percona XtraDB Cluster (PXC) 5.5.28-23.7 and newer, but there are three limitations you should consider before archiving on a cluster:

Error on commit

pt-archiver does not check for error when it commits transactions. Commits on PXC can fail, but the tool does not yet check for or retry the transaction when this happens. If it happens, the tool will die.

MyISAM tables

Archiving MyISAM tables works, but MyISAM support in PXC is still experimental at the time of this release. There are several known bugs with PXC, MyISAM tables, and AUTO_INCREMENT columns. Therefore, you must ensure that archiving will not directly or indirectly result in the use of default AUTO_INCREMENT values for a MyISAM table. For example, this happens with --dest if --columns is used and the AUTO_INCREMENT column is not included. The tool does not check for this!

Non-cluster options

Certain options may or may not work. For example, if a cluster node is not also a slave, then --check-slave-lag does not work. And since PXC tables are usually InnoDB, but InnoDB doesn’t support INSERT DELAYED, then --delayed-insert does not work. Other options may also not work, but the tool does not check them, therefore you should test archiving on a test cluster before archiving on your real cluster.

OUTPUT

If you specify --progress, the output is a header row, plus status output at intervals. Each row in the status output lists the current date and time, how many seconds pt-archiver has been running, and how many rows it has archived.

If you specify --statistics, pt-archiver outputs timing and other information to help you identify which part of your archiving process takes the most time.

ERROR-HANDLING

pt-archiver tries to catch signals and exit gracefully; for example, if you send it SIGTERM (Ctrl-C on UNIX-ish systems), it will catch the signal, print a message about the signal, and exit fairly normally. It will not execute --analyze or --optimize, because these may take a long time to finish. It will run all other code normally, including calling after_finish() on any plugins (see “EXTENDING”).

In other words, a signal, if caught, will break out of the main archiving loop and skip optimize/analyze.

OPTIONS

Specify at least one of --dest, --file, or --purge.

--ignore and --replace are mutually exclusive.

--txn-size and --commit-each are mutually exclusive.

--low-priority-insert and --delayed-insert are mutually exclusive.

--share-lock and --for-update are mutually exclusive.

--analyze and --optimize are mutually exclusive.

--no-ascend and --no-delete are mutually exclusive.

DSN values in --dest default to values from --source if COPY is yes.

--analyze

type: string

Run ANALYZE TABLE afterwards on --source and/or --dest.

Runs ANALYZE TABLE after finishing. The argument is an arbitrary string. If it contains the letter ‘s’, the source will be analyzed. If it contains ‘d’, the destination will be analyzed. You can specify either or both. For example, the following will analyze both:

--analyze=ds

See http://dev.mysql.com/doc/en/analyze-table.html for details on ANALYZE TABLE.

--ascend-first

Ascend only first column of index.

If you do want to use the ascending index optimization (see --no-ascend), but do not want to incur the overhead of ascending a large multi-column index, you can use this option to tell pt-archiver to ascend only the leftmost column of the index. This can provide a significant performance boost over not ascending the index at all, while avoiding the cost of ascending the whole index.

See “EXTENDING” for a discussion of how this interacts with plugins.

--ask-pass

Prompt for a password when connecting to MySQL.

--buffer

Buffer output to --file and flush at commit.

Disables autoflushing to --file and flushes --file to disk only when a transaction commits. This typically means the file is block-flushed by the operating system, so there may be some implicit flushes to disk between commits as well. The default is to flush --file to disk after every row.

The danger is that a crash might cause lost data.

The performance increase I have seen from using --buffer is around 5 to 15 percent. Your mileage may vary.

--bulk-delete

Delete each chunk with a single statement (implies --commit-each).

Delete each chunk of rows in bulk with a single DELETE statement. The statement deletes every row between the first and last row of the chunk, inclusive. It implies --commit-each, since it would be a bad idea to INSERT rows one at a time and commit them before the bulk DELETE.

The normal method is to delete every row by its primary key. Bulk deletes might be a lot faster. They also might not be faster if you have a complex WHERE clause.

This option completely defers all DELETE processing until the chunk of rows is finished. If you have a plugin on the source, its before_delete method will not be called. Instead, its before_bulk_delete method is called later.

WARNING: if you have a plugin on the source that sometimes doesn’t return true from is_archivable(), you should use this option only if you understand what it does. If the plugin instructs pt-archiver not to archive a row, it will still be deleted by the bulk delete!

--[no]bulk-delete-limit

default: yes

Add --limit to --bulk-delete statement.

This is an advanced option and you should not disable it unless you know what you are doing and why! By default, --bulk-delete appends a --limit clause to the bulk delete SQL statement. In certain cases, this clause can be omitted by specifying --no-bulk-delete-limit. --limit must still be specified.

--bulk-insert

Insert each chunk with LOAD DATA INFILE (implies --bulk-delete --commit-each).

Insert each chunk of rows with LOAD DATA LOCAL INFILE. This may be much faster than inserting a row at a time with INSERT statements. It is implemented by creating a temporary file for each chunk of rows, and writing the rows to this file instead of inserting them. When the chunk is finished, it uploads the rows.

To protect the safety of your data, this option forces bulk deletes to be used. It would be unsafe to delete each row as it is found, before inserting the rows into the destination first. Forcing bulk deletes guarantees that the deletion waits until the insertion is successful.

The --low-priority-insert, --replace, and --ignore options work with this option, but --delayed-insert does not.

If LOAD DATA LOCAL INFILE throws an error in the lines of The used command is not allowed with this MySQL version, refer to the documentation for the L DSN option.

--charset

short form: -A; type: string

Default character set. If the value is utf8, sets Perl’s binmode on STDOUT to utf8, passes the mysql_enable_utf8 option to DBD::mysql, and runs SET NAMES UTF8 after connecting to MySQL. Any other value sets binmode on STDOUT without the utf8 layer, and runs SET NAMES after connecting to MySQL.

Note that only charsets as known by MySQL are recognized; So for example, “UTF8” will work, but “UTF-8” will not.

See also --[no]check-charset.

--[no]check-charset

default: yes

Ensure connection and table character sets are the same. Disabling this check may cause text to be erroneously converted from one character set to another (usually from utf8 to latin1) which may cause data loss or mojibake. Disabling this check may be useful or necessary when character set conversions are intended.

--[no]check-columns

default: yes

Ensure --source and --dest have same columns.

Enabled by default; causes pt-archiver to check that the source and destination tables have the same columns. It does not check column order, data type, etc. It just checks that all columns in the source exist in the destination and vice versa. If there are any differences, pt-archiver will exit with an error.

To disable this check, specify –no-check-columns.

--check-interval

type: time; default: 1s

How often to check for slave lag if --check-slave-lag is given.

--check-slave-lag

type: string

Pause archiving until the specified DSN’s slave lag is less than --max-lag.

--columns

short form: -c; type: array

Comma-separated list of columns to archive.

Specify a comma-separated list of columns to fetch, write to the file, and insert into the destination table. If specified, pt-archiver ignores other columns unless it needs to add them to the SELECT statement for ascending an index or deleting rows. It fetches and uses these extra columns internally, but does not write them to the file or to the destination table. It does pass them to plugins.

See also --primary-key-only.

--commit-each

Commit each set of fetched and archived rows (disables --txn-size).

Commits transactions and flushes --file after each set of rows has been archived, before fetching the next set of rows, and before sleeping if --sleep is specified. Disables --txn-size; use --limit to control the transaction size with --commit-each.

This option is useful as a shortcut to make --limit and --txn-size the same value, but more importantly it avoids transactions being held open while searching for more rows. For example, imagine you are archiving old rows from the beginning of a very large table, with --limit 1000 and --txn-size 1000. After some period of finding and archiving 1000 rows at a time, pt-archiver finds the last 999 rows and archives them, then executes the next SELECT to find more rows. This scans the rest of the table, but never finds any more rows. It has held open a transaction for a very long time, only to determine it is finished anyway. You can use --commit-each to avoid this.

--config

type: Array

Read this comma-separated list of config files; if specified, this must be the first option on the command line.

--database

short form: -D; type: string

Connect to this database.

--delayed-insert

Add the DELAYED modifier to INSERT statements.

Adds the DELAYED modifier to INSERT or REPLACE statements. See http://dev.mysql.com/doc/en/insert.html for details.

--dest

type: DSN

DSN specifying the table to archive to.

This item specifies a table into which pt-archiver will insert rows archived from --source. It uses the same key=val argument format as --source. Most missing values default to the same values as --source, so you don’t have to repeat options that are the same in --source and --dest. Use the --help option to see which values are copied from --source.

WARNING: Using a default options file (F) DSN option that defines a socket for --source causes pt-archiver to connect to --dest using that socket unless another socket for --dest is specified. This means that pt-archiver may incorrectly connect to --source when it connects to --dest. For example:

--source F=host1.cnf,D=db,t=tbl --dest h=host2

When pt-archiver connects to --dest, host2, it will connect via the --source, host1, socket defined in host1.cnf.

--dry-run

Print queries and exit without doing anything.

Causes pt-archiver to exit after printing the filename and SQL statements it will use.

--file

type: string

File to archive to, with DATE_FORMAT()-like formatting.

Filename to write archived rows to. A subset of MySQL’s DATE_FORMAT() formatting codes are allowed in the filename, as follows:

%d    Day of the month, numeric (01..31)
%H    Hour (00..23)
%i    Minutes, numeric (00..59)
%m    Month, numeric (01..12)
%s    Seconds (00..59)
%Y    Year, numeric, four digits

You can use the following extra format codes too:

%D    Database name
%t    Table name

Example:

--file '/var/log/archive/%Y-%m-%d-%D.%t'

The file’s contents are in the same format used by SELECT INTO OUTFILE, as documented in the MySQL manual: rows terminated by newlines, columns terminated by tabs, NULL characters are represented by N, and special characters are escaped by . This lets you reload a file with LOAD DATA INFILE’s default settings.

If you want a column header at the top of the file, see --header. The file is auto-flushed by default; see --buffer.

--for-update

Adds the FOR UPDATE modifier to SELECT statements.

For details, see http://dev.mysql.com/doc/en/innodb-locking-reads.html.

--header

Print column header at top of --file.

Writes column names as the first line in the file given by --file. If the file exists, does not write headers; this keeps the file loadable with LOAD DATA INFILE in case you append more output to it.

--help

Show help and exit.

--high-priority-select

Adds the HIGH_PRIORITY modifier to SELECT statements.

See http://dev.mysql.com/doc/en/select.html for details.

--host

short form: -h; type: string

Connect to host.

--ignore

Use IGNORE for INSERT statements.

Causes INSERTs into --dest to be INSERT IGNORE.

--limit

type: int; default: 1

Number of rows to fetch and archive per statement.

Limits the number of rows returned by the SELECT statements that retrieve rows to archive. Default is one row. It may be more efficient to increase the limit, but be careful if you are archiving sparsely, skipping over many rows; this can potentially cause more contention with other queries, depending on the storage engine, transaction isolation level, and options such as --for-update.

--local

Do not write OPTIMIZE or ANALYZE queries to binlog.

Adds the NO_WRITE_TO_BINLOG modifier to ANALYZE and OPTIMIZE queries. See --analyze for details.

--low-priority-delete

Adds the LOW_PRIORITY modifier to DELETE statements.

See http://dev.mysql.com/doc/en/delete.html for details.

--low-priority-insert

Adds the LOW_PRIORITY modifier to INSERT or REPLACE statements.

See http://dev.mysql.com/doc/en/insert.html for details.

--max-lag

type: time; default: 1s

Pause archiving if the slave given by --check-slave-lag lags.

This option causes pt-archiver to look at the slave every time it’s about to fetch another row. If the slave’s lag is greater than the option’s value, or if the slave isn’t running (so its lag is NULL), pt-table-checksum sleeps for --check-interval seconds and then looks at the lag again. It repeats until the slave is caught up, then proceeds to fetch and archive the row.

This option may eliminate the need for --sleep or --sleep-coef.

--no-ascend

Do not use ascending index optimization.

The default ascending-index optimization causes pt-archiver to optimize repeated SELECT queries so they seek into the index where the previous query ended, then scan along it, rather than scanning from the beginning of the table every time. This is enabled by default because it is generally a good strategy for repeated accesses.

Large, multiple-column indexes may cause the WHERE clause to be complex enough that this could actually be less efficient. Consider for example a four-column PRIMARY KEY on (a, b, c, d). The WHERE clause to start where the last query ended is as follows:

WHERE (a > ?)
   OR (a = ? AND b > ?)
   OR (a = ? AND b = ? AND c > ?)
   OR (a = ? AND b = ? AND c = ? AND d >= ?)

Populating the placeholders with values uses memory and CPU, adds network traffic and parsing overhead, and may make the query harder for MySQL to optimize. A four-column key isn’t a big deal, but a ten-column key in which every column allows NULL might be.

Ascending the index might not be necessary if you know you are simply removing rows from the beginning of the table in chunks, but not leaving any holes, so starting at the beginning of the table is actually the most efficient thing to do.

See also --ascend-first. See “EXTENDING” for a discussion of how this interacts with plugins.

--no-delete

Do not delete archived rows.

Causes pt-archiver not to delete rows after processing them. This disallows --no-ascend, because enabling them both would cause an infinite loop.

If there is a plugin on the source DSN, its before_delete method is called anyway, even though pt-archiver will not execute the delete. See “EXTENDING” for more on plugins.

--optimize

type: string

Run OPTIMIZE TABLE afterwards on --source and/or --dest.

Runs OPTIMIZE TABLE after finishing. See --analyze for the option syntax and http://dev.mysql.com/doc/en/optimize-table.html for details on OPTIMIZE TABLE.

--password

short form: -p; type: string

Password to use when connecting.

--pid

type: string

Create the given PID file. The tool won’t start if the PID file already exists and the PID it contains is different than the current PID. However, if the PID file exists and the PID it contains is no longer running, the tool will overwrite the PID file with the current PID. The PID file is removed automatically when the tool exits.

--plugin

type: string

Perl module name to use as a generic plugin.

Specify the Perl module name of a general-purpose plugin. It is currently used only for statistics (see --statistics) and must have new() and a statistics() method.

The new( src = $src, dst => $dst, opts => $o )> method gets the source and destination DSNs, and their database connections, just like the connection-specific plugins do. It also gets an OptionParser object ($o) for accessing command-line options (example: ``$o-``get(‘purge’);>).

The statistics(\%stats, $time) method gets a hashref of the statistics collected by the archiving job, and the time the whole job started.

--port

short form: -P; type: int

Port number to use for connection.

--primary-key-only

Primary key columns only.

A shortcut for specifying --columns with the primary key columns. This is an efficiency if you just want to purge rows; it avoids fetching the entire row, when only the primary key columns are needed for DELETE statements. See also --purge.

--progress

type: int

Print progress information every X rows.

Prints current time, elapsed time, and rows archived every X rows.

--purge

Purge instead of archiving; allows omitting --file and --dest.

Allows archiving without a --file or --dest argument, which is effectively a purge since the rows are just deleted.

If you just want to purge rows, consider specifying the table’s primary key columns with --primary-key-only. This will prevent fetching all columns from the server for no reason.

--quick-delete

Adds the QUICK modifier to DELETE statements.

See http://dev.mysql.com/doc/en/delete.html for details. As stated in the documentation, in some cases it may be faster to use DELETE QUICK followed by OPTIMIZE TABLE. You can use --optimize for this.

--quiet

short form: -q

Do not print any output, such as for --statistics.

Suppresses normal output, including the output of --statistics, but doesn’t suppress the output from --why-quit.

--replace

Causes INSERTs into --dest to be written as REPLACE.

--retries

type: int; default: 1

Number of retries per timeout or deadlock.

Specifies the number of times pt-archiver should retry when there is an InnoDB lock wait timeout or deadlock. When retries are exhausted, pt-archiver will exit with an error.

Consider carefully what you want to happen when you are archiving between a mixture of transactional and non-transactional storage engines. The INSERT to --dest and DELETE from --source are on separate connections, so they do not actually participate in the same transaction even if they’re on the same server. However, pt-archiver implements simple distributed transactions in code, so commits and rollbacks should happen as desired across the two connections.

At this time I have not written any code to handle errors with transactional storage engines other than InnoDB. Request that feature if you need it.

--run-time

type: time

Time to run before exiting.

Optional suffix s=seconds, m=minutes, h=hours, d=days; if no suffix, s is used.

--[no]safe-auto-increment

default: yes

Do not archive row with max AUTO_INCREMENT.

Adds an extra WHERE clause to prevent pt-archiver from removing the newest row when ascending a single-column AUTO_INCREMENT key. This guards against re-using AUTO_INCREMENT values if the server restarts, and is enabled by default.

The extra WHERE clause contains the maximum value of the auto-increment column as of the beginning of the archive or purge job. If new rows are inserted while pt-archiver is running, it will not see them.

--sentinel

type: string; default: /tmp/pt-archiver-sentinel

Exit if this file exists.

The presence of the file specified by --sentinel will cause pt-archiver to stop archiving and exit. The default is /tmp/pt-archiver-sentinel. You might find this handy to stop cron jobs gracefully if necessary. See also --stop.

--set-vars

type: Array

Set the MySQL variables in this comma-separated list of variable=value pairs.

By default, the tool sets:

wait_timeout=10000

Variables specified on the command line override these defaults. For example, specifying --set-vars wait_timeout=500 overrides the default value of 10000.

The tool prints a warning and continues if a variable cannot be set.

--share-lock

Adds the LOCK IN SHARE MODE modifier to SELECT statements.

See http://dev.mysql.com/doc/en/innodb-locking-reads.html.

--skip-foreign-key-checks

Disables foreign key checks with SET FOREIGN_KEY_CHECKS=0.

--sleep

type: int

Sleep time between fetches.

Specifies how long to sleep between SELECT statements. Default is not to sleep at all. Transactions are NOT committed, and the --file file is NOT flushed, before sleeping. See --txn-size to control that.

If --commit-each is specified, committing and flushing happens before sleeping.

--sleep-coef

type: float

Calculate --sleep as a multiple of the last SELECT time.

If this option is specified, pt-archiver will sleep for the query time of the last SELECT multiplied by the specified coefficient.

This is a slightly more sophisticated way to throttle the SELECTs: sleep a varying amount of time between each SELECT, depending on how long the SELECTs are taking.

--socket

short form: -S; type: string

Socket file to use for connection.

--source

type: DSN

DSN specifying the table to archive from (required). This argument is a DSN. See DSN OPTIONS for the syntax. Most options control how pt-archiver connects to MySQL, but there are some extended DSN options in this tool’s syntax. The D, t, and i options select a table to archive:

--source h=my_server,D=my_database,t=my_tbl

The a option specifies the database to set as the connection’s default with USE. If the b option is true, it disables binary logging with SQL_LOG_BIN. The m option specifies pluggable actions, which an external Perl module can provide. The only required part is the table; other parts may be read from various places in the environment (such as options files).

The ‘i’ part deserves special mention. This tells pt-archiver which index it should scan to archive. This appears in a FORCE INDEX or USE INDEX hint in the SELECT statements used to fetch archivable rows. If you don’t specify anything, pt-archiver will auto-discover a good index, preferring a PRIMARY KEY if one exists. In my experience this usually works well, so most of the time you can probably just omit the ‘i’ part.

The index is used to optimize repeated accesses to the table; pt-archiver remembers the last row it retrieves from each SELECT statement, and uses it to construct a WHERE clause, using the columns in the specified index, that should allow MySQL to start the next SELECT where the last one ended, rather than potentially scanning from the beginning of the table with each successive SELECT. If you are using external plugins, please see “EXTENDING” for a discussion of how they interact with ascending indexes.

The ‘a’ and ‘b’ options allow you to control how statements flow through the binary log. If you specify the ‘b’ option, binary logging will be disabled on the specified connection. If you specify the ‘a’ option, the connection will USE the specified database, which you can use to prevent slaves from executing the binary log events with --replicate-ignore-db options. These two options can be used as different methods to achieve the same goal: archive data off the master, but leave it on the slave. For example, you can run a purge job on the master and prevent it from happening on the slave using your method of choice.

WARNING: Using a default options file (F) DSN option that defines a socket for --source causes pt-archiver to connect to --dest using that socket unless another socket for --dest is specified. This means that pt-archiver may incorrectly connect to --source when it is meant to connect to --dest. For example:

--source F=host1.cnf,D=db,t=tbl --dest h=host2

When pt-archiver connects to --dest, host2, it will connect via the --source, host1, socket defined in host1.cnf.

--statistics

Collect and print timing statistics.

Causes pt-archiver to collect timing statistics about what it does. These statistics are available to the plugin specified by --plugin

Unless you specify --quiet, pt-archiver prints the statistics when it exits. The statistics look like this:

Started at 2008-07-18T07:18:53, ended at 2008-07-18T07:18:53
Source: D=db,t=table
SELECT 4
INSERT 4
DELETE 4
Action         Count       Time        Pct
commit            10     0.1079      88.27
select             5     0.0047       3.87
deleting           4     0.0028       2.29
inserting          4     0.0028       2.28
other              0     0.0040       3.29

The first two (or three) lines show times and the source and destination tables. The next three lines show how many rows were fetched, inserted, and deleted.

The remaining lines show counts and timing. The columns are the action, the total number of times that action was timed, the total time it took, and the percent of the program’s total runtime. The rows are sorted in order of descending total time. The last row is the rest of the time not explicitly attributed to anything. Actions will vary depending on command-line options.

If --why-quit is given, its behavior is changed slightly. This option causes it to print the reason for exiting even when it’s just because there are no more rows.

This option requires the standard Time::HiRes module, which is part of core Perl on reasonably new Perl releases.

--stop

Stop running instances by creating the sentinel file.

Causes pt-archiver to create the sentinel file specified by --sentinel and exit. This should have the effect of stopping all running instances which are watching the same sentinel file.

--txn-size

type: int; default: 1

Number of rows per transaction.

Specifies the size, in number of rows, of each transaction. Zero disables transactions altogether. After pt-archiver processes this many rows, it commits both the --source and the --dest if given, and flushes the file given by --file.

This parameter is critical to performance. If you are archiving from a live server, which for example is doing heavy OLTP work, you need to choose a good balance between transaction size and commit overhead. Larger transactions create the possibility of more lock contention and deadlocks, but smaller transactions cause more frequent commit overhead, which can be significant. To give an idea, on a small test set I worked with while writing pt-archiver, a value of 500 caused archiving to take about 2 seconds per 1000 rows on an otherwise quiet MySQL instance on my desktop machine, archiving to disk and to another table. Disabling transactions with a value of zero, which turns on autocommit, dropped performance to 38 seconds per thousand rows.

If you are not archiving from or to a transactional storage engine, you may want to disable transactions so pt-archiver doesn’t try to commit.

--user

short form: -u; type: string

User for login if not current user.

--version

Show version and exit.

--[no]version-check

default: yes

Check for the latest version of Percona Toolkit, MySQL, and other programs.

This is a standard “check for updates automatically” feature, with two additional features. First, the tool checks the version of other programs on the local system in addition to its own version. For example, it checks the version of every MySQL server it connects to, Perl, and the Perl module DBD::mysql. Second, it checks for and warns about versions with known problems. For example, MySQL 5.5.25 had a critical bug and was re-released as 5.5.25a.

Any updates or known problems are printed to STDOUT before the tool’s normal output. This feature should never interfere with the normal operation of the tool.

For more information, visit https://www.percona.com/version-check.

--where

type: string

WHERE clause to limit which rows to archive (required).

Specifies a WHERE clause to limit which rows are archived. Do not include the word WHERE. You may need to quote the argument to prevent your shell from interpreting it. For example:

--where 'ts < current_date - interval 90 day'

For safety, --where is required. If you do not require a WHERE clause, use --where 1=1.

--why-quit

Print reason for exiting unless rows exhausted.

Causes pt-archiver to print a message if it exits for any reason other than running out of rows to archive. This can be useful if you have a cron job with --run-time specified, for example, and you want to be sure pt-archiver is finishing before running out of time.

If --statistics is given, the behavior is changed slightly. It will print the reason for exiting even when it’s just because there are no more rows.

This output prints even if --quiet is given. That’s so you can put pt-archiver in a cron job and get an email if there’s an abnormal exit.

DSN OPTIONS

These DSN options are used to create a DSN. Each option is given like option=value. The options are case-sensitive, so P and p are not the same option. There cannot be whitespace before or after the = and if the value contains whitespace it must be quoted. DSN options are comma-separated. See the percona-toolkit manpage for full details.

  • a

copy: no

Database to USE when executing queries.

  • A

dsn: charset; copy: yes

Default character set.

  • b

copy: no

If true, disable binlog with SQL_LOG_BIN.

  • D

dsn: database; copy: yes

Database that contains the table.

  • F

dsn: mysql_read_default_file; copy: yes

Only read default options from the given file

  • h

dsn: host; copy: yes

Connect to host.

  • i

copy: yes

Index to use.

  • L

copy: yes

Explicitly enable LOAD DATA LOCAL INFILE.

For some reason, some vendors compile libmysql without the –enable-local-infile option, which disables the statement. This can lead to weird situations, like the server allowing LOCAL INFILE, but the client throwing exceptions if it’s used.

However, as long as the server allows LOAD DATA, clients can easily reenable it; See https://dev.mysql.com/doc/refman/5.0/en/load-data-local.html and http://search.cpan.org/~capttofu/DBD-mysql/lib/DBD/mysql.pm. This option does exactly that.

Although we’ve not found a case where turning this option leads to errors or differing behavior, to be on the safe side, this option is not on by default.

  • m

copy: no

Plugin module name.

  • p

dsn: password; copy: yes

Password to use when connecting.

  • P

dsn: port; copy: yes

Port number to use for connection.

  • S

dsn: mysql_socket; copy: yes

Socket file to use for connection.

  • t

copy: yes

Table to archive from/to.

  • u

dsn: user; copy: yes

User for login if not current user.

EXTENDING

pt-archiver is extensible by plugging in external Perl modules to handle some logic and/or actions. You can specify a module for both the --source and the --dest, with the ‘m’ part of the specification. For example:

--source D=test,t=test1,m=My::Module1 --dest m=My::Module2,t=test2

This will cause pt-archiver to load the My::Module1 and My::Module2 packages, create instances of them, and then make calls to them during the archiving process.

You can also specify a plugin with --plugin.

The module must provide this interface:

new(dbh => $dbh, db => $db_name, tbl => $tbl_name)

The plugin’s constructor is passed a reference to the database handle, the database name, and table name. The plugin is created just after pt-archiver opens the connection, and before it examines the table given in the arguments. This gives the plugin a chance to create and populate temporary tables, or do other setup work.

before_begin(cols => @cols, allcols => @allcols)

This method is called just before pt-archiver begins iterating through rows and archiving them, but after it does all other setup work (examining table structures, designing SQL queries, and so on). This is the only time pt-archiver tells the plugin column names for the rows it will pass the plugin while archiving.

The cols argument is the column names the user requested to be archived, either by default or by the --columns option. The allcols argument is the list of column names for every row pt-archiver will fetch from the source table. It may fetch more columns than the user requested, because it needs some columns for its own use. When subsequent plugin functions receive a row, it is the full row containing all the extra columns, if any, added to the end.

is_archivable(row => @row)

This method is called for each row to determine whether it is archivable. This applies only to --source. The argument is the row itself, as an arrayref. If the method returns true, the row will be archived; otherwise it will be skipped.

Skipping a row adds complications for non-unique indexes. Normally pt-archiver uses a WHERE clause designed to target the last processed row as the place to start the scan for the next SELECT statement. If you have skipped the row by returning false from is_archivable(), pt-archiver could get into an infinite loop because the row still exists. Therefore, when you specify a plugin for the --source argument, pt-archiver will change its WHERE clause slightly. Instead of starting at “greater than or equal to” the last processed row, it will start “strictly greater than.” This will work fine on unique indexes such as primary keys, but it may skip rows (leave holes) on non-unique indexes or when ascending only the first column of an index.

pt-archiver will change the clause in the same way if you specify --no-delete, because again an infinite loop is possible.

If you specify the --bulk-delete option and return false from this method, pt-archiver may not do what you want. The row won’t be archived, but it will be deleted, since bulk deletes operate on ranges of rows and don’t know which rows the plugin selected to keep.

If you specify the --bulk-insert option, this method’s return value will influence whether the row is written to the temporary file for the bulk insert, so bulk inserts will work as expected. However, bulk inserts require bulk deletes.

before_delete(row => @row)

This method is called for each row just before it is deleted. This applies only to --source. This is a good place for you to handle dependencies, such as deleting things that are foreign-keyed to the row you are about to delete. You could also use this to recursively archive all dependent tables.

This plugin method is called even if --no-delete is given, but not if --bulk-delete is given.

before_bulk_delete(first_row => @row, last_row => @row)

This method is called just before a bulk delete is executed. It is similar to the before_delete method, except its arguments are the first and last row of the range to be deleted. It is called even if --no-delete is given.

before_insert(row => @row)

This method is called for each row just before it is inserted. This applies only to --dest. You could use this to insert the row into multiple tables, perhaps with an ON DUPLICATE KEY UPDATE clause to build summary tables in a data warehouse.

This method is not called if --bulk-insert is given.

before_bulk_insert(first_row => @row, last_row => @row, filename => bulk_insert_filename)

This method is called just before a bulk insert is executed. It is similar to the before_insert method, except its arguments are the first and last row of the range to be deleted.

custom_sth(row => @row, sql => $sql)

This method is called just before inserting the row, but after “before_insert()”. It allows the plugin to specify different INSERT statement if desired. The return value (if any) should be a DBI statement handle. The sql parameter is the SQL text used to prepare the default INSERT statement. This method is not called if you specify --bulk-insert.

If no value is returned, the default INSERT statement handle is used.

This method applies only to the plugin specified for --dest, so if your plugin isn’t doing what you expect, check that you’ve specified it for the destination and not the source.

custom_sth_bulk(first_row => @row, last_row => @row, sql => $sql, filename => $bulk_insert_filename)

If you’ve specified --bulk-insert, this method is called just before the bulk insert, but after “before_bulk_insert()”, and the arguments are different.

This method’s return value etc is similar to the “custom_sth()” method.

after_finish()

This method is called after pt-archiver exits the archiving loop, commits all database handles, closes --file, and prints the final statistics, but before pt-archiver runs ANALYZE or OPTIMIZE (see --analyze and --optimize).

If you specify a plugin for both --source and --dest, pt-archiver constructs, calls before_begin(), and calls after_finish() on the two plugins in the order --source, --dest.

pt-archiver assumes it controls transactions, and that the plugin will NOT commit or roll back the database handle. The database handle passed to the plugin’s constructor is the same handle pt-archiver uses itself. Remember that --source and --dest are separate handles.

A sample module might look like this:

package My::Module;

sub new {
   my ( $class, %args ) = @_;
   return bless(\%args, $class);
}

sub before_begin {
   my ( $self, %args ) = @_;
   # Save column names for later
   $self->{cols} = $args{cols};
}

sub is_archivable {
   my ( $self, %args ) = @_;
   # Do some advanced logic with $args{row}
   return 1;
}

sub before_delete {} # Take no action
sub before_insert {} # Take no action
sub custom_sth    {} # Take no action
sub after_finish  {} # Take no action

1;

ENVIRONMENT

The environment variable PTDEBUG enables verbose debugging output to STDERR. To enable debugging and capture all output to a file, run the tool like:

PTDEBUG=1 pt-archiver ... > FILE 2>&1

Be careful: debugging output is voluminous and can generate several megabytes of output.

SYSTEM REQUIREMENTS

You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.

BUGS

For a list of known bugs, see http://www.percona.com/bugs/pt-archiver.

Please report bugs at https://bugs.launchpad.net/percona-toolkit. Include the following information in your bug report:

  • Complete command-line used to run the tool
  • Tool --version
  • MySQL version of all servers involved
  • Output from the tool including STDERR
  • Input files (log/dump/config files, etc.)

If possible, include debugging output by running the tool with PTDEBUG; see “ENVIRONMENT”.

DOWNLOADING

Visit http://www.percona.com/software/percona-toolkit/ to download the latest release of Percona Toolkit. Or, get the latest release from the command line:

wget percona.com/get/percona-toolkit.tar.gz

wget percona.com/get/percona-toolkit.rpm

wget percona.com/get/percona-toolkit.deb

You can also get individual tools from the latest release:

wget percona.com/get/TOOL

Replace TOOL with the name of any tool.

AUTHORS

Baron Schwartz

ACKNOWLEDGMENTS

Andrew O’Brien

ABOUT PERCONA TOOLKIT

This tool is part of Percona Toolkit, a collection of advanced command-line tools for MySQL developed by Percona. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and primarily developed by him and Daniel Nichter. Visit http://www.percona.com/software/ to learn about other free, open-source software from Percona.

VERSION

pt-archiver 2.2.12

Percona Toolkit
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