pt-archiverp - Online in the Cloud

PROGRAM:

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

If "--check-slave-lag" is given, this defines how long the tool pauses each
time it discovers that a slave is lagging.
This check is performed every 100 rows.

--check-slave-lag
type: string; repeatable: yes

Pause archiving until the specified DSN's slave lag is less than "--max-lag". This
option can be specified multiple times for checking more than one slave.

--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-flow-ctl
type: float

Somewhat similar to --max-lag but for PXC clusters. Check average time cluster spent
pausing for Flow Control and make tool pause if it goes over the percentage indicated
in the option. Default is no Flow Control checking. This option is available for PXC
versions 5.6 or higher.

--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. If password contains commas they must be escaped
with a backslash: "exam\,ple"

--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 re-enable 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. If password contains commas they must be escaped
with a backslash: "exam\,ple"

· 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.

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