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PT-TABLE-CHECKSUM(1)  User Contributed Perl Documentation PT-TABLE-CHECKSUM(1)

NAME
       pt-table-checksum - Verify MySQL	replication integrity.

SYNOPSIS
       Usage: pt-table-checksum	[OPTIONS] [DSN]

       pt-table-checksum performs an online replication	consistency check by
       executing checksum queries on the master, which produces	different
       results on replicas that	are inconsistent with the master.  The
       optional	DSN specifies the master host.	The tool's "EXIT STATUS" is
       non-zero	if any differences are found, or if any	warnings or errors
       occur.

       The following command will connect to the replication master on
       localhost, checksum every table,	and report the results on every
       detected	replica:

	  pt-table-checksum

       This tool is focused on finding data differences	efficiently.  If any
       data is different, you can resolve the problem with pt-table-sync.

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:

       o   Read	the tool's documentation

       o   Review the tool's known "BUGS"

       o   Test	the tool on a non-production server

       o   Backup your production server and verify the	backups

       See also	"LIMITATIONS".

DESCRIPTION
       pt-table-checksum is designed to	do the right thing by default in
       almost every case.  When	in doubt, use "--explain" to see how the tool
       will checksum a table.  The following is	a high-level overview of how
       the tool	functions.

       In contrast to older versions of	pt-table-checksum, this	tool is
       focused on a single purpose, and	does not have a	lot of complexity or
       support many different checksumming techniques.	It executes checksum
       queries on only one server, and these flow through replication to re-
       execute on replicas.  If	you need the older behavior, you can use
       Percona Toolkit version 1.0.

       pt-table-checksum connects to the server	you specify, and finds
       databases and tables that match the filters you specify (if any).  It
       works one table at a time, so it	does not accumulate large amounts of
       memory or do a lot of work before beginning to checksum.	 This makes it
       usable on very large servers. We	have used it on	servers	with hundreds
       of thousands of databases and tables, and trillions of rows.  No	matter
       how large the server is,	pt-table-checksum works	equally	well.

       One reason it can work on very large tables is that it divides each
       table into chunks of rows, and checksums	each chunk with	a single
       REPLACE..SELECT query.  It varies the chunk size	to make	the checksum
       queries run in the desired amount of time.  The goal of chunking	the
       tables, instead of doing	each table with	a single big query, is to
       ensure that checksums are unintrusive and don't cause too much
       replication lag or load on the server.  That's why the target time for
       each chunk is 0.5 seconds by default.

       The tool	keeps track of how quickly the server is able to execute the
       queries,	and adjusts the	chunks as it learns more about the server's
       performance.  It	uses an	exponentially decaying weighted	average	to
       keep the	chunk size stable, yet remain responsive if the	server's
       performance changes during checksumming for any reason.	This means
       that the	tool will quickly throttle itself if your server becomes
       heavily loaded during a traffic spike or	a background task, for
       example.

       Chunking	is accomplished	by a technique that we used to call "nibbling"
       in other	tools in Percona Toolkit.  It is the same technique used for
       pt-archiver, for	example.  The legacy chunking algorithms used in older
       versions	of pt-table-checksum are removed, because they did not result
       in predictably sized chunks, and	didn't work well on many tables.  All
       that is required	to divide a table into chunks is an index of some sort
       (preferably a primary key or unique index).  If there is	no index, and
       the table contains a suitably small number of rows, the tool will
       checksum	the table in a single chunk.

       pt-table-checksum has many other	safeguards to ensure that it does not
       interfere with any server's operation, including	replicas.  To
       accomplish this,	pt-table-checksum detects replicas and connects	to
       them automatically.  (If	this fails, you	can give it a hint with	the
       "--recursion-method" option.)

       The tool	monitors replicas continually.	If any replica falls too far
       behind in replication, pt-table-checksum	pauses to allow	it to catch
       up.  If any replica has an error, or replication	stops, pt-table-
       checksum	pauses and waits.  In addition,	pt-table-checksum looks	for
       common causes of	problems, such as replication filters, and refuses to
       operate unless you force	it to.	Replication filters are	dangerous,
       because the queries that	pt-table-checksum executes could potentially
       conflict	with them and cause replication	to fail.

       pt-table-checksum verifies that chunks are not too large	to checksum
       safely. It performs an EXPLAIN query on each chunk, and skips chunks
       that might be larger than the desired number of rows. You can configure
       the sensitivity of this safeguard with the "--chunk-size-limit" option.
       If a table will be checksummed in a single chunk	because	it has a small
       number of rows, then pt-table-checksum additionally verifies that the
       table isn't oversized on	replicas.  This	avoids the following scenario:
       a table is empty	on the master but is very large	on a replica, and is
       checksummed in a	single large query, which causes a very	long delay in
       replication.

       There are several other safeguards. For example,	pt-table-checksum sets
       its session-level innodb_lock_wait_timeout to 1 second, so that if
       there is	a lock wait, it	will be	the victim instead of causing other
       queries to time out.  Another safeguard checks the load on the database
       server, and pauses if the load is too high. There is no single right
       answer for how to do this, but by default pt-table-checksum will	pause
       if there	are more than 25 concurrently executing	queries.  You should
       probably	set a sane value for your server with the "--max-load" option.

       Checksumming usually is a low-priority task that	should yield to	other
       work on the server. However, a tool that	must be	restarted constantly
       is difficult to use.  Thus, pt-table-checksum is	very resilient to
       errors.	For example, if	the database administrator needs to kill pt-
       table-checksum's	queries	for any	reason,	that is	not a fatal error.
       Users often run pt-kill to kill any long-running	checksum queries. The
       tool will retry a killed	query once, and	if it fails again, it will
       move on to the next chunk of that table.	 The same behavior applies if
       there is	a lock wait timeout.  The tool will print a warning if such an
       error happens, but only once per	table.	If the connection to any
       server fails, pt-table-checksum will attempt to reconnect and continue
       working.

       If pt-table-checksum encounters a condition that	causes it to stop
       completely, it is easy to resume	it with	the "--resume" option. It will
       begin from the last chunk of the	last table that	it processed.  You can
       also safely stop	the tool with CTRL-C.  It will finish the chunk	it is
       currently processing, and then exit.  You can resume it as usual
       afterwards.

       After pt-table-checksum finishes	checksumming all of the	chunks in a
       table, it pauses	and waits for all detected replicas to finish
       executing the checksum queries.	Once that is finished, it checks all
       of the replicas to see if they have the same data as the	master,	and
       then prints a line of output with the results.  You can see a sample of
       its output later	in this	documentation.

       The tool	prints progress	indicators during time-consuming operations.
       It prints a progress indicator as each table is checksummed.  The
       progress	is computed by the estimated number of rows in the table. It
       will also print a progress report when it pauses	to wait	for
       replication to catch up,	and when it is waiting to check	replicas for
       differences from	the master.  You can make the output less verbose with
       the "--quiet" option.

       If you wish, you	can query the checksum tables manually to get a	report
       of which	tables and chunks have differences from	the master.  The
       following query will report every database and table with differences,
       along with a summary of the number of chunks and	rows possibly
       affected:

	 SELECT	db, tbl, SUM(this_cnt) AS total_rows, COUNT(*) AS chunks
	 FROM percona.checksums
	 WHERE (
	  master_cnt <>	this_cnt
	  OR master_crc	<> this_crc
	  OR ISNULL(master_crc)	<> ISNULL(this_crc))
	 GROUP BY db, tbl;

       The table referenced in that query is the checksum table, where the
       checksums are stored.  Each row in the table contains the checksum of
       one chunk of data from some table in the	server.

       Version 2.0 of pt-table-checksum	is not backwards compatible with pt-
       table-sync version 1.0.	In some	cases this is not a serious problem.
       Adding a	"boundaries" column to the table, and then updating it with a
       manually	generated WHERE	clause,	may suffice to let pt-table-sync
       version 1.0 interoperate	with pt-table-checksum version 2.0.  Assuming
       an integer primary key named 'id', You can try something	like the
       following:

	 ALTER TABLE checksums ADD boundaries VARCHAR(500);
	 UPDATE	checksums
	  SET boundaries = COALESCE(CONCAT('id BETWEEN ', lower_boundary,
	     ' AND ', upper_boundary), '1=1');

LIMITATIONS
       Replicas	using row-based	replication
	   pt-table-checksum requires statement-based replication, and it sets
	   "binlog_format=STATEMENT" on	the master, but	due to a MySQL
	   limitation replicas do not honor this change.  Therefore, checksums
	   will	not replicate past any replicas	using row-based	replication
	   that	are masters for	further	replicas.

	   The tool automatically checks the "binlog_format" on	all servers.
	   See "--[no]check-binlog-format" .

	   (Bug	899415 <https://bugs.launchpad.net/percona-
	   toolkit/+bug/899415>)

       Schema and table	differences
	   The tool presumes that schemas and tables are identical on the
	   master and all replicas.  Replication will break if,	for example, a
	   replica does	not have a schema that exists on the master (and that
	   schema is checksummed), or if the structure of a table on a replica
	   is different	than on	the master.

Percona	XtraDB Cluster
       pt-table-checksum works with Percona XtraDB Cluster (PXC) 5.5.28-23.7
       and newer.  The number of possible Percona XtraDB Cluster setups	is
       large given that	it can be used with regular replication	as well.
       Therefore, only the setups listed below are supported and known to
       work.  Other setups, like cluster to cluster, are not support and
       probably	don't work.

       Except where noted, all of the following	supported setups require that
       you use the "dsn" method	for "--recursion-method" to specify cluster
       nodes.  Also, the lag check (see	"REPLICA CHECKS") is not performed for
       cluster nodes.

       Single cluster
	   The simplest	PXC setup is a single cluster: all servers are cluster
	   nodes, and there are	no regular replicas.  If all nodes are
	   specified in	the DSN	table (see "--recursion-method"), then you can
	   run the tool	on any node and	any diffs on any other nodes will be
	   detected.

	   All nodes must be in	the same cluster (have the same
	   "wsrep_cluster_name"	value),	else the tool exits with an error.
	   Although it's possible to have different clusters with the same
	   name, this should not be done and is	not supported.	This applies
	   to all supported setups.

       Single cluster with replicas
	   Cluster nodes can also be regular masters and replicate to regular
	   replicas.  However, the tool	can only detect	diffs on a replica if
	   ran on the replica's	"master	node".	For example, if	the cluster
	   setup is,

	      node1 <->	node2 <-> node3
			  |	    |
			  |	    +->	replica3
			  +-> replica2

	   you can detect diffs	on replica3 by running the tool	on node3, but
	   to detect diffs on replica2 you must	run the	tool again on node2.
	   If you run the tool on node1, it will not detect diffs on either
	   replica.

	   Currently, the tool does not	detect this setup or warn about
	   replicas that cannot	be checked (e.g. replica2 when running on
	   node3).

	   Replicas in this setup are still subject to
	   "--[no]check-binlog-format".

       Master to single	cluster
	   It is possible for a	regular	master to replicate to a cluster, as
	   if the cluster were one logical slave, like:

	      master ->	node1 <-> node2	<-> node3

	   The tool supports this setup	but only if ran	on the master and if
	   all nodes in	the cluster are	consistent with	the "direct replica"
	   (node1 in this example) of the master.  For example,	if all nodes
	   have	value "foo" for	row 1 but the master has value "bar" for the
	   same	row, this diff will be detected.  Or if	only node1 has this
	   diff, it will also be detected.  But	if only	node2 or node3 has
	   this	diff, it will not be detected.	Therefore, this	setup is used
	   to check that the master and	the cluster as a whole are consistent.

	   In this setup, the tool can automatically detect the	"direct
	   replica" (node1) when ran on	the master, so you do not have to use
	   the "dsn" method for	"--recursion-method" because node1 will
	   represent the entire	cluster, which is why all other	nodes must be
	   consistent with it.

	   The tool warns when it detects this setup to	remind you that	it
	   only	works when used	as described above.  These warnings do not
	   affect the exit status of the tool; they're only reminders to help
	   avoid false-positive	results.

OUTPUT
       The tool	prints tabular results,	one line per table:

		     TS	ERRORS	DIFFS  ROWS  CHUNKS SKIPPED    TIME TABLE
	 10-20T08:36:50	     0	    0	200	  1	  0   0.005 db1.tbl1
	 10-20T08:36:50	     0	    0	603	  7	  0   0.035 db1.tbl2
	 10-20T08:36:50	     0	    0	 16	  1	  0   0.003 db2.tbl3
	 10-20T08:36:50	     0	    0	600	  6	  0   0.024 db2.tbl4

       Errors, warnings, and progress reports are printed to standard error.
       See also	"--quiet".

       Each table's results are	printed	when the tool finishes checksumming
       the table.  The columns are as follows:

       TS  The timestamp (without the year) when the tool finished
	   checksumming	the table.

       ERRORS
	   The number of errors	and warnings that occurred while checksumming
	   the table.  Errors and warnings are printed to standard error while
	   the table is	in progress.

       DIFFS
	   The number of chunks	that differ from the master on one or more
	   replicas.  If "--no-replicate-check"	is specified, this column will
	   always have zeros.  If "--replicate-check-only" is specified, then
	   only	tables with differences	are printed.

       ROWS
	   The number of rows selected and checksummed from the	table.	It
	   might be different from the number of rows in the table if you use
	   the --where option.

       CHUNKS
	   The number of chunks	into which the table was divided.

       SKIPPED
	   The number of chunks	that were skipped due one or more of these
	   problems:

	      *	MySQL not using	the --chunk-index
	      *	MySQL not using	the full chunk index (--[no]check-plan)
	      *	Chunk size is greater than --chunk-size	* --chunk-size-limit
	      *	Lock wait timeout exceeded (--retries)
	      *	Checksum query killed (--retries)

	   As of pt-table-checksum 2.2.5, skipped chunks cause a non-zero
	   "EXIT STATUS".

       TIME
	   The time elapsed while checksumming the table.

       TABLE
	   The database	and table that was checksummed.

       If "--replicate-check-only" is specified, only checksum differences on
       detected	replicas are printed.  The output is different:	one paragraph
       per replica, one	checksum difference per	line, and values are separated
       by spaces:

	 Differences on	h=127.0.0.1,P=12346
	 TABLE CHUNK CNT_DIFF CRC_DIFF CHUNK_INDEX LOWER_BOUNDARY UPPER_BOUNDARY
	 db1.tbl1 1 0 1	PRIMARY	1 100
	 db1.tbl1 6 0 1	PRIMARY	501 600

	 Differences on	h=127.0.0.1,P=12347
	 TABLE CHUNK CNT_DIFF CRC_DIFF CHUNK_INDEX LOWER_BOUNDARY UPPER_BOUNDARY
	 db1.tbl1 1 0 1	PRIMARY	1 100
	 db2.tbl2 9 5 0	PRIMARY	101 200

       The first line of a paragraph indicates the replica with	differences.
       In this example there are two: h=127.0.0.1,P=12346 and
       h=127.0.0.1,P=12347.  The columns are as	follows:

       TABLE
	   The database	and table that differs from the	master.

       CHUNK
	   The chunk number of the table that differs from the master.

       CNT_DIFF
	   The number of chunk rows on the replica minus the number of chunk
	   rows	on the master.

       CRC_DIFF
	   1 if	the CRC	of the chunk on	the replica is different than the CRC
	   of the chunk	on the master, else 0.

       CHUNK_INDEX
	   The index used to chunk the table.

       LOWER_BOUNDARY
	   The index values that define	the lower boundary of the chunk.

       UPPER_BOUNDARY
	   The index values that define	the upper boundary of the chunk.

EXIT STATUS
       pt-table-checksum has three possible exit statuses: zero, 255, and any
       other value is a	bitmask	with flags for different problems.

       A zero exit status indicates no errors, warnings, or checksum
       differences, or skipped chunks or tables.

       A 255 exit status indicates a fatal error.  In other words: the tool
       died or crashed.	 The error is printed to "STDERR".

       If the exit status is not zero or 255, then its value functions as a
       bitmask with these flags:

	  FLAG		    BIT	VALUE  MEANING
	  ================  =========  ==========================================
	  ERROR			    1  A non-fatal error occurred
	  ALREADY_RUNNING	    2  --pid file exists and the PID is	running
	  CAUGHT_SIGNAL		    4  Caught SIGHUP, SIGINT, SIGPIPE, or SIGTERM
	  NO_SLAVES_FOUND	    8  No replicas or cluster nodes were found
	  TABLE_DIFF		   16  At least	one diff was found
	  SKIP_CHUNK		   32  At least	one chunk was skipped
	  SKIP_TABLE		   64  At least	one table was skipped

       If any flag is set, the exit status will	be non-zero.  Use the bitwise
       "AND" operation to check	for a particular flag.	For example, if
       "$exit_status & 16" is true, then at least one diff was found.

       As of pt-table-checksum 2.2.5, skipped chunks cause a non-zero exit
       status.	An exit	status of zero or 32 is	equivalent to a	zero exit
       status with skipped chunks in previous versions of the tool.

OPTIONS
       This tool accepts additional command-line arguments.  Refer to the
       "SYNOPSIS" and usage information	for details.

       --ask-pass
	   group: Connection

	   Prompt for a	password when connecting to MySQL.

       --[no]check-binlog-format
	   default: yes

	   Check that the "binlog_format" is the same on all servers.

	   See "Replicas using row-based replication" under "LIMITATIONS".

       --binary-index
	   This	option modifies	the behavior of	"--create-replicate-table"
	   such	that the replicate table's upper and lower boundary columns
	   are created with the	BLOB data type.	 This is useful	in cases where
	   you have trouble checksuming	tables with keys that include a	binary
	   data	type or	that have non-standard character sets.	See
	   "--replicate".

       --check-interval
	   type: time; default:	1; group: Throttle

	   Sleep time between checks for "--max-lag".

       --[no]check-plan
	   default: yes

	   Check query execution plans for safety. By default, this option
	   causes pt-table-checksum to run EXPLAIN before running queries that
	   are meant to	access a small amount of data, but which could access
	   many	rows if	MySQL chooses a	bad execution plan. These include the
	   queries to determine	chunk boundaries and the chunk queries
	   themselves. If it appears that MySQL	will use a bad query execution
	   plan, the tool will skip the	chunk of the table.

	   The tool uses several heuristics to determine whether an execution
	   plan	is bad.	 The first is whether EXPLAIN reports that MySQL
	   intends to use the desired index to access the rows.	If MySQL
	   chooses a different index, the tool considers the query unsafe.

	   The tool also checks	how much of the	index MySQL reports that it
	   will	use for	the query. The EXPLAIN output shows this in the
	   key_len column. The tool remembers the largest key_len seen,	and
	   skips chunks	where MySQL reports that it will use a smaller prefix
	   of the index. This heuristic	can be understood as skipping chunks
	   that	have a worse execution plan than other chunks.

	   The tool prints a warning the first time a chunk is skipped due to
	   a bad execution plan	in each	table. Subsequent chunks are skipped
	   silently, although you can see the count of skipped chunks in the
	   SKIPPED column in the tool's	output.

	   This	option adds some setup work to each table and chunk. Although
	   the work is not intrusive for MySQL,	it results in more round-trips
	   to the server, which	consumes time. Making chunks too small will
	   cause the overhead to become	relatively larger. It is therefore
	   recommended that you	not make chunks	too small, because the tool
	   may take a very long	time to	complete if you	do.

       --[no]check-replication-filters
	   default: yes; group:	Safety

	   Do not checksum if any replication filters are set on any replicas.
	   The tool looks for server options that filter replication, such as
	   binlog_ignore_db and	replicate_do_db.  If it	finds any such
	   filters, it aborts with an error.

	   If the replicas are configured with any filtering options, you
	   should be careful not to checksum any databases or tables that
	   exist on the	master and not the replicas.  Changes to such tables
	   might normally be skipped on	the replicas because of	the filtering
	   options, but	the checksum queries modify the	contents of the	table
	   that	stores the checksums, not the tables whose data	you are
	   checksumming.  Therefore, these queries will	be executed on the
	   replica, and	if the table or	database you're	checksumming does not
	   exist, the queries will cause replication to	fail.  For more
	   information on replication rules, see
	   <http://dev.mysql.com/doc/en/replication-rules.html>.

	   Replication filtering makes it impossible to	be sure	that the
	   checksum queries won't break	replication (or	simply fail to
	   replicate).	If you are sure	that it's OK to	run the	checksum
	   queries, you	can negate this	option to disable the checks.  See
	   also	"--replicate-database".

	   See also "REPLICA CHECKS".

       --check-slave-lag
	   type: string; group:	Throttle

	   Pause checksumming until this replica's lag is less than
	   "--max-lag".	 The value is a	DSN that inherits properties from the
	   master host and the connection options ("--port", "--user", etc.).
	   By default, pt-table-checksum monitors lag on all connected
	   replicas, but this option limits lag	monitoring to the specified
	   replica.  This is useful if certain replicas	are intentionally
	   lagged (with	pt-slave-delay for example), in	which case you can
	   specify a normal replica to monitor.

	   See also "REPLICA CHECKS".

       --[no]check-slave-tables
	   default: yes; group:	Safety

	   Checks that tables on slaves	exist and have all the checksum
	   "--columns".	 Tables	missing	on slaves or not having	all the
	   checksum "--columns"	can cause the tool to break replication	when
	   it tries to check for differences.  Only disable this check if you
	   are aware of	the risks and are sure that all	tables on all slaves
	   exist and are identical to the master.

       --chunk-index
	   type: string

	   Prefer this index for chunking tables.  By default, pt-table-
	   checksum chooses the	most appropriate index for chunking.  This
	   option lets you specify the index that you prefer.  If the index
	   doesn't exist, then pt-table-checksum will fall back	to its default
	   behavior of choosing	an index.  pt-table-checksum adds the index to
	   the checksum	SQL statements in a "FORCE INDEX" clause.  Be careful
	   when	using this option; a poor choice of index could	cause bad
	   performance.	 This is probably best to use when you are
	   checksumming	only a single table, not an entire server.

       --chunk-index-columns
	   type: int

	   Use only this many left-most	columns	of a "--chunk-index".  This
	   works only for compound indexes, and	is useful in cases where a bug
	   in the MySQL	query optimizer	(planner) causes it to scan a large
	   range of rows instead of using the index to locate starting and
	   ending points precisely.  This problem sometimes occurs on indexes
	   with	many columns, such as 4	or more.  If this happens, the tool
	   might print a warning related to the	"--[no]check-plan" option.
	   Instructing the tool	to use only the	first N	columns	of the index
	   is a	workaround for the bug in some cases.

       --chunk-size
	   type: size; default:	1000

	   Number of rows to select for	each checksum query.  Allowable
	   suffixes are	k, M, G.  You should not use this option in most
	   cases; prefer "--chunk-time"	instead.

	   This	option can override the	default	behavior, which	is to adjust
	   chunk size dynamically to try to make chunks	run in exactly
	   "--chunk-time" seconds.  When this option isn't set explicitly, its
	   default value is used as a starting point, but after	that, the tool
	   ignores this	option's value.	 If you	set this option	explicitly,
	   however, then it disables the dynamic adjustment behavior and tries
	   to make all chunks exactly the specified number of rows.

	   There is a subtlety:	if the chunk index is not unique, then it's
	   possible that chunks	will be	larger than desired. For example, if a
	   table is chunked by an index	that contains 10,000 of	a given	value,
	   there is no way to write a WHERE clause that	matches	only 1,000 of
	   the values, and that	chunk will be at least 10,000 rows large.
	   Such	a chunk	will probably be skipped because of
	   "--chunk-size-limit".

	   Selecting a small chunk size	will cause the tool to become much
	   slower, in part because of the setup	work required for
	   "--[no]check-plan".

       --chunk-size-limit
	   type: float;	default: 2.0; group: Safety

	   Do not checksum chunks this much larger than	the desired chunk
	   size.

	   When	a table	has no unique indexes, chunk sizes can be inaccurate.
	   This	option specifies a maximum tolerable limit to the inaccuracy.
	   The tool uses <EXPLAIN> to estimate how many	rows are in the	chunk.
	   If that estimate exceeds the	desired	chunk size times the limit
	   (twice as large, by default), then the tool skips the chunk.

	   The minimum value for this option is	1, which means that no chunk
	   can be larger than "--chunk-size".  You probably don't want to
	   specify 1, because rows reported by EXPLAIN are estimates, which
	   can be different from the real number of rows in the	chunk.	If the
	   tool	skips too many chunks because they are oversized, you might
	   want	to specify a value larger than the default of 2.

	   You can disable oversized chunk checking by specifying a value of
	   0.

       --chunk-time
	   type: float;	default: 0.5

	   Adjust the chunk size dynamically so	each checksum query takes this
	   long	to execute.

	   The tool tracks the checksum	rate (rows per second) for all tables
	   and each table individually.	 It uses these rates to	adjust the
	   chunk size after each checksum query, so that the next checksum
	   query takes this amount of time (in seconds)	to execute.

	   The algorithm is as follows:	at the beginning of each table,	the
	   chunk size is initialized from the overall average rows per second
	   since the tool began	working, or the	value of "--chunk-size"	if the
	   tool	hasn't started working yet. For	each subsequent	chunk of a
	   table, the tool adjusts the chunk size to try to make queries run
	   in the desired amount of time.  It keeps an exponentially decaying
	   moving average of queries per second, so that if the	server's
	   performance changes due to changes in server	load, the tool adapts
	   quickly.  This allows the tool to achieve predictably timed queries
	   for each table, and for the server overall.

	   If this option is set to zero, the chunk size doesn't auto-adjust,
	   so query checksum times will	vary, but query	checksum sizes will
	   not.	Another	way to do the same thing is to specify a value for
	   "--chunk-size" explicitly, instead of leaving it at the default.

       --columns
	   short form: -c; type: array;	group: Filter

	   Checksum only this comma-separated list of columns.	If a table
	   doesn't have	any of the specified columns it	will be	skipped.

	   This	option applies to all tables, so it really only	makes sense
	   when	checksumming one table unless the tables have a	common set of
	   columns.

       --config
	   type: Array;	group: Config

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

	   See the "--help" output for a list of default config	files.

       --[no]create-replicate-table
	   default: yes

	   Create the "--replicate" database and table if they do not exist.
	   The structure of the	replicate table	is the same as the suggested
	   table mentioned in "--replicate".

       --databases
	   short form: -d; type: hash; group: Filter

	   Only	checksum this comma-separated list of databases.

       --databases-regex
	   type: string; group:	Filter

	   Only	checksum databases whose names match this Perl regex.

       --defaults-file
	   short form: -F; type: string; group:	Connection

	   Only	read mysql options from	the given file.	 You must give an
	   absolute pathname.

       --[no]empty-replicate-table
	   default: yes

	   Delete previous checksums for each table before checksumming	the
	   table.  This	option does not	truncate the entire table, it only
	   deletes rows	(checksums) for	each table just	before checksumming
	   the table.  Therefore, if checksumming stops	prematurely and	there
	   was preexisting data, there will still be rows for tables that were
	   not checksummed before the tool was stopped.

	   If you're resuming from a previous checksum run, then the checksum
	   records for the table from which the	tool resumes won't be emptied.

	   To empty the	entire replicate table,	you must manually execute
	   "TRUNCATE TABLE" before running the tool.

       --engines
	   short form: -e; type: hash; group: Filter

	   Only	checksum tables	which use these	storage	engines.

       --explain
	   cumulative: yes; default: 0;	group: Output

	   Show, but do	not execute, checksum queries (disables
	   "--[no]empty-replicate-table").  If specified twice,	the tool
	   actually iterates through the chunking algorithm, printing the
	   upper and lower boundary values for each chunk, but not executing
	   the checksum	queries.

       --float-precision
	   type: int

	   Precision for FLOAT and DOUBLE number-to-string conversion.	Causes
	   FLOAT and DOUBLE values to be rounded to the	specified number of
	   digits after	the decimal point, with	the ROUND() function in	MySQL.
	   This	can help avoid checksum	mismatches due to different floating-
	   point representations of the	same values on different MySQL
	   versions and	hardware.  The default is no rounding; the values are
	   converted to	strings	by the CONCAT()	function, and MySQL chooses
	   the string representation.  If you specify a	value of 2, for
	   example, then the values 1.008 and 1.009 will be rounded to 1.01,
	   and will checksum as	equal.

       --function
	   type: string

	   Hash	function for checksums (FNV1A_64, MURMUR_HASH, SHA1, MD5,
	   CRC32, etc).

	   The default is to use CRC32(), but MD5() and	SHA1() also work, and
	   you can use your own	function, such as a compiled UDF, if you wish.
	   The function	you specify is run in SQL, not in Perl,	so it must be
	   available to	MySQL.

	   MySQL doesn't have good built-in hash functions that	are fast.
	   CRC32() is too prone	to hash	collisions, and	MD5() and SHA1() are
	   very	CPU-intensive. The FNV1A_64() UDF that is distributed with
	   Percona Server is a faster alternative.  It is very simple to
	   compile and install;	look at	the header in the source code for
	   instructions.  If it	is installed, it is preferred over MD5().  You
	   can also use	the MURMUR_HASH() function if you compile and install
	   that	as a UDF; the source is	also distributed with Percona Server,
	   and it might	be better than FNV1A_64().

       --help
	   group: Help

	   Show	help and exit.

       --host
	   short form: -h; type: string; default: localhost; group: Connection

	   Host	to connect to.

       --ignore-columns
	   type: Hash; group: Filter

	   Ignore this comma-separated list of columns when calculating	the
	   checksum.  If a table has all of its	columns	filtered by
	   --ignore-columns, it	will be	skipped.

       --ignore-databases
	   type: Hash; group: Filter

	   Ignore this comma-separated list of databases.

       --ignore-databases-regex
	   type: string; group:	Filter

	   Ignore databases whose names	match this Perl	regex.

       --ignore-engines
	   type: Hash; default:	FEDERATED,MRG_MyISAM; group: Filter

	   Ignore this comma-separated list of storage engines.

       --ignore-tables
	   type: Hash; group: Filter

	   Ignore this comma-separated list of tables.	Table names may	be
	   qualified with the database name.  The "--replicate"	table is
	   always automatically	ignored.

       --ignore-tables-regex
	   type: string; group:	Filter

	   Ignore tables whose names match the Perl regex.

       --max-lag
	   type: time; default:	1s; group: Throttle

	   Pause checksumming until all	replicas' lag is less than this	value.
	   After each checksum query (each chunk), pt-table-checksum looks at
	   the replication lag of all replicas to which	it connects, using
	   Seconds_Behind_Master. If any replica is lagging more than the
	   value of this option, then pt-table-checksum	will sleep for
	   "--check-interval" seconds, then check all replicas again.  If you
	   specify "--check-slave-lag",	then the tool only examines that
	   server for lag, not all servers.

	   The tool waits forever for replicas to stop lagging.	 If any
	   replica is stopped, the tool	waits forever until the	replica	is
	   started.  Checksumming continues once all replicas are running and
	   not lagging too much.

	   The tool prints progress reports while waiting.  If a replica is
	   stopped, it prints a	progress report	immediately, then again	at
	   every progress report interval.

	   See also "REPLICA CHECKS".

       --max-load
	   type: Array;	default: Threads_running=25; group: Throttle

	   Examine SHOW	GLOBAL STATUS after every chunk, and pause if any
	   status variables are	higher than the	threshold.  The	option accepts
	   a comma-separated list of MySQL status variables to check for a
	   threshold.  An optional "=MAX_VALUE"	(or ":MAX_VALUE") can follow
	   each	variable.  If not given, the tool determines a threshold by
	   examining the current value and increasing it by 20%.

	   For example,	if you want the	tool to	pause when Threads_connected
	   gets	too high, you can specify "Threads_connected", and the tool
	   will	check the current value	when it	starts working and add 20% to
	   that	value.	If the current value is	100, then the tool will	pause
	   when	Threads_connected exceeds 120, and resume working when it is
	   below 120 again.  If	you want to specify an explicit	threshold,
	   such	as 110,	you can	use either "Threads_connected:110" or
	   "Threads_connected=110".

	   The purpose of this option is to prevent the	tool from adding too
	   much	load to	the server. If the checksum queries are	intrusive, or
	   if they cause lock waits, then other	queries	on the server will
	   tend	to block and queue. This will typically	cause Threads_running
	   to increase,	and the	tool can detect	that by	running	SHOW GLOBAL
	   STATUS immediately after each checksum query	finishes.  If you
	   specify a threshold for this	variable, then you can instruct	the
	   tool	to wait	until queries are running normally again.  This	will
	   not prevent queueing, however; it will only give the	server a
	   chance to recover from the queueing.	 If you	notice queueing, it is
	   best	to decrease the	chunk time.

       --password
	   short form: -p; type: string; group:	Connection

	   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 file that defines a "pt_table_checksum_plugin" class.
	   A plugin allows you to write	a Perl module that can hook into many
	   parts of pt-table-checksum.	This requires a	good knowledge of Perl
	   and Percona Toolkit conventions, which are beyond this scope	of
	   this	documentation.	Please contact Percona if you have questions
	   or need help.

	   See "PLUGIN"	for more information.

       --port
	   short form: -P; type: int; group: Connection

	   Port	number to use for connection.

       --progress
	   type: array;	default: time,30

	   Print progress reports to STDERR.

	   The value is	a comma-separated list with two	parts.	The first part
	   can be percentage, time, or iterations; the second part specifies
	   how often an	update should be printed, in percentage, seconds, or
	   number of iterations.  The tool prints progress reports for a
	   variety of time-consuming operations, including waiting for
	   replicas to catch up	if they	become lagged.

       --quiet
	   short form: -q; cumulative: yes; default: 0

	   Print only the most important information (disables "--progress").
	   Specifying this option once causes the tool to print	only errors,
	   warnings, and tables	that have checksum differences.

	   Specifying this option twice	causes the tool	to print only errors.
	   In this case, you can use the tool's	exit status to determine if
	   there were any warnings or checksum differences.

       --recurse
	   type: int

	   Number of levels to recurse in the hierarchy	when discovering
	   replicas.  Default is infinite.  See	also "--recursion-method" and
	   "REPLICA CHECKS".

       --recursion-method
	   type: array;	default: processlist,hosts

	   Preferred recursion method for discovering replicas.	 pt-table-
	   checksum performs several "REPLICA CHECKS" before and while
	   running.

	   Although replicas are not required to run pt-table-checksum,	the
	   tool	cannot detect diffs on slaves that it cannot discover.
	   Therefore, a	warning	is printed and the "EXIT STATUS" is non-zero
	   if no replicas are found and	the method is not "none".  If this
	   happens, try	a different recursion method, or use the "dsn" method
	   to specify the replicas to check.

	   Possible methods are:

	     METHOD	  USES
	     ===========  =============================================
	     processlist  SHOW PROCESSLIST
	     hosts	  SHOW SLAVE HOSTS
	     cluster	  SHOW STATUS LIKE 'wsrep\_incoming\_addresses'
	     dsn=DSN	  DSNs from a table
	     none	  Do not find slaves

	   The "processlist" method is the default, because "SHOW SLAVE	HOSTS"
	   is not reliable.  However, if the server uses a non-standard	port
	   (not	3306), then the	"hosts"	method becomes the default because it
	   works better	in this	case.

	   The "hosts" method requires replicas	to be configured with
	   "report_host", "report_port", etc.

	   The "cluster" method	requires a cluster based on Galera 23.7.3 or
	   newer, such as Percona XtraDB Cluster versions 5.5.29 and above.
	   This	will auto-discover nodes in a cluster using "SHOW STATUS LIKE
	   'wsrep\_incoming\_addresses'".  You can combine "cluster" with
	   "processlist" and "hosts" to	auto-discover cluster nodes and
	   replicas, but this functionality is experimental.

	   The "dsn" method is special:	rather than automatically discovering
	   replicas, this method specifies a table with	replica	DSNs.  The
	   tool	will only connect to these replicas.  This method works	best
	   when	replicas do not	use the	same MySQL username or password	as the
	   master, or when you want to prevent the tool	from connecting	to
	   certain replicas.  The "dsn"	method is specified like:
	   "--recursion-method dsn=h=host,D=percona,t=dsns".  The specified
	   DSN must have D and t parts,	or just	a database-qualified t part,
	   which specify the DSN table.	 The DSN table must have the following
	   structure:

	     CREATE TABLE `dsns` (
	       `id` int(11) NOT	NULL AUTO_INCREMENT,
	       `parent_id` int(11) DEFAULT NULL,
	       `dsn` varchar(255) NOT NULL,
	       PRIMARY KEY (`id`)
	     );

	   DSNs	are ordered by "id", but "id" and "parent_id" are otherwise
	   ignored.  The "dsn" column contains a replica DSN like it would be
	   given on the	command	line, for example:
	   "h=replica_host,u=repl_user,p=repl_pass".

	   The "none" method makes the tool ignore all slaves and cluster
	   nodes. This method is not recommended because it effectively
	   disables the	"REPLICA CHECKS" and no	differences can	be found. It
	   is useful, however, if you only need	to write checksums on the
	   master or a single cluster node. The	safer alternative is
	   "--no-replicate-check": the tool finds replicas and cluster nodes,
	   performs the	"REPLICA CHECKS", but does not check for differences.
	   See "--[no]replicate-check".

       --replicate
	   type: string; default: percona.checksums

	   Write checksum results to this table.  The replicate	table must
	   have	this structure (MAGIC_create_replicate):

	     CREATE TABLE checksums (
		db	       CHAR(64)	    NOT	NULL,
		tbl	       CHAR(64)	    NOT	NULL,
		chunk	       INT	    NOT	NULL,
		chunk_time     FLOAT		NULL,
		chunk_index    VARCHAR(200)	NULL,
		lower_boundary TEXT		NULL,
		upper_boundary TEXT		NULL,
		this_crc       CHAR(40)	    NOT	NULL,
		this_cnt       INT	    NOT	NULL,
		master_crc     CHAR(40)		NULL,
		master_cnt     INT		NULL,
		ts	       TIMESTAMP    NOT	NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
		PRIMARY	KEY (db, tbl, chunk),
		INDEX ts_db_tbl	(ts, db, tbl)
	     ) ENGINE=InnoDB;

	   Note: lower_boundary	and upper_boundary data	type can be BLOB. See
	   "--binary-index".

	   By default, "--[no]create-replicate-table" is true, so the database
	   and the table specified by this option are created automatically if
	   they	do not exist.

	   Be sure to choose an	appropriate storage engine for the replicate
	   table.  If you are checksumming InnoDB tables, and you use MyISAM
	   for this table, a deadlock will break replication, because the
	   mixture of transactional and	non-transactional tables in the
	   checksum statements will cause it to	be written to the binlog even
	   though it had an error.  It will then replay	without	a deadlock on
	   the replicas, and break replication with "different error on	master
	   and slave."	This is	not a problem with pt-table-checksum; it's a
	   problem with	MySQL replication, and you can read more about it in
	   the MySQL manual.

	   The replicate table is never	checksummed (the tool automatically
	   adds	this table to "--ignore-tables").

       --[no]replicate-check
	   default: yes

	   Check replicas for data differences after finishing each table.
	   The tool finds differences by executing a simple SELECT statement
	   on all detected replicas.  The query	compares the replica's
	   checksum results to the master's checksum results.  It reports
	   differences in the DIFFS column of the output.

       --replicate-check-only
	   Check replicas for consistency without executing checksum queries.
	   This	option is used only with "--[no]replicate-check".  If
	   specified, pt-table-checksum	doesn't	checksum any tables.  It
	   checks replicas for differences found by previous checksumming, and
	   then	exits.	It might be useful if you run pt-table-checksum
	   quietly in a	cron job, for example, and later want a	report on the
	   results of the cron job, perhaps to implement a Nagios check.

       --replicate-check-retries
	   type: int; default: 1

	   Retry checksum comparison this many times when a difference is
	   encountered.	 Only when a difference	persists after this number of
	   checks is it	considered valid.  Using this option with a value of 2
	   or more alleviates spurious differences that	arise when using the
	   --resume option.

       --replicate-database
	   type: string

	   USE only this database.  By default,	pt-table-checksum executes USE
	   to select the database that contains	the table it's currently
	   working on.	This is	is a best effort to avoid problems with
	   replication filters such as binlog_ignore_db	and
	   replicate_ignore_db.	 However, replication filters can create a
	   situation where there simply	is no one right	way to do things.
	   Some	statements might not be	replicated, and	others might cause
	   replication to fail.	 In such cases,	you can	use this option	to
	   specify a default database that pt-table-checksum selects with USE,
	   and never changes.  See also	"--[no]check-replication-filters".

       --resume
	   Resume checksumming from the	last completed chunk (disables
	   "--[no]empty-replicate-table").  If the tool	stops before it
	   checksums all tables, this option makes checksumming	resume from
	   the last chunk of the last table that it finished.

       --retries
	   type: int; default: 2

	   Retry a chunk this many times when there is a nonfatal error.
	   Nonfatal errors are problems	such as	a lock wait timeout or the
	   query being killed.

       --run-time
	   type: time

	   How long to run.  Default is	to run until all tables	have been
	   checksummed.	 These time value suffixes are allowed:	s (seconds), m
	   (minutes), h	(hours), and d (days).	Combine	this option with
	   "--resume" to checksum as many tables within	an allotted time,
	   resuming from where the tool	left off next time it is ran.

       --separator
	   type: string; default: #

	   The separator character used	for CONCAT_WS().  This character is
	   used	to join	the values of columns when checksumming.

       --set-vars
	   type: Array;	group: Connection

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

	   By default, the tool	sets:

	      wait_timeout=10000
	      innodb_lock_wait_timeout=1

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

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

       --socket
	   short form: -S; type: string; group:	Connection

	   Socket file to use for connection.

       --slave-skip-tolerance
	   type: float;	default: 1.0

	   When	a master table is marked to be checksumed in only one chunk
	   but a slave table exceeds the maximum accepted size for this, the
	   table is skipped.  Since number of rows are often rough estimates,
	   many	times tables are skipped needlessly for	very small
	   differences.	 This option provides a	max row	excess tolerance to
	   prevent this.  For example a	value of 1.2 will tolerate slave
	   tables with up to 20% excess	rows.

       --tables
	   short form: -t; type: hash; group: Filter

	   Checksum only this comma-separated list of tables.  Table names may
	   be qualified	with the database name.

       --tables-regex
	   type: string; group:	Filter

	   Checksum only tables	whose names match this Perl regex.

       --trim
	   Add TRIM() to VARCHAR columns (helps	when comparing 4.1 to >= 5.0).
	   This	is useful when you don't care about the	trailing space
	   differences between MySQL versions that vary	in their handling of
	   trailing spaces. MySQL 5.0 and later	all retain trailing spaces in
	   VARCHAR, while previous versions would remove them.	These
	   differences will cause false	checksum differences.

       --user
	   short form: -u; type: string; group:	Connection

	   User	for login if not current user.

       --version
	   group: Help

	   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

	   Do only rows	matching this WHERE clause.  You can use this option
	   to limit the	checksum to only part of the table.  This is
	   particularly	useful if you have append-only tables and don't	want
	   to constantly re-check all rows; you	could run a daily job to just
	   check yesterday's rows, for instance.

	   This	option is much like the	-w option to mysqldump.	 Do not
	   specify the WHERE keyword.  You might need to quote the value.
	   Here	is an example:

	     pt-table-checksum --where "ts > CURRENT_DATE - INTERVAL 1 DAY"

REPLICA	CHECKS
       By default, pt-table-checksum attempts to find and connect to all
       replicas	connected to the master	host.  This automated process is
       called "slave recursion"	and is controlled by the "--recursion-method"
       and "--recurse" options.	 The tool performs these checks	on all
       replicas:

       1. "--[no]check-replication-filters"
	   pt-table-checksum checks for	replication filters on all replicas
	   because they	can complicate or break	the checksum process.  By
	   default, the	tool will exit if any replication filters are found,
	   but this check can be disabled by specifying
	   "--no-check-replication-filters".

       2. "--replicate"	table
	   pt-table-checksum checks that the "--replicate" table exists	on all
	   replicas, else checksumming can break replication when updates to
	   the table on	the master replicate to	a replica that doesn't have
	   the table.  This check cannot be disabled, and the tool waits
	   forever until the table exists on all replicas, printing
	   "--progress"	messages while it waits.

       3. Single chunk size
	   If a	table can be checksummed in a single chunk on the master, pt-
	   table-checksum will check that the table size on all	replicas is
	   less	than "--chunk-size" * "--chunk-size-limit". This prevents a
	   rare	problem	where the table	on the master is empty or small, but
	   on a	replica	it is much larger. In this case, the single chunk
	   checksum on the master would	overload the replica.

	   Another rare	problem	occurs when the	table size on a	replica	is
	   close to "--chunk-size" * "--chunk-size-limit". In such cases, the
	   table is more likely	to be skipped even though it's safe to
	   checksum in a single	chunk.	This happens because table sizes are
	   estimates. When those estimates and "--chunk-size" *
	   "--chunk-size-limit"	are almost equal, this check becomes more
	   sensitive to	the estimates' margin of error rather than actual
	   significant differences in table sizes. Specifying a	larger value
	   for "--chunk-size-limit" helps avoid	this problem.

	   This	check cannot be	disabled.

       4. Lag
	   After each chunk, pt-table-checksum checks the lag on all replicas,
	   or only the replica specified by "--check-slave-lag".  This helps
	   the tool not	to overload the	replicas with checksum data.  There is
	   no way to disable this check, but you can specify a single replica
	   to check with "--check-slave-lag", and if that replica is the
	   fastest, it will help prevent the tool from waiting too long	for
	   replica lag to abate.

       5. Checksum chunks
	   When	pt-table-checksum finishes checksumming	a table, it waits for
	   the last checksum chunk to replicate	to all replicas	so it can
	   perform the "--[no]replicate-check".	 Disabling that	option by
	   specifying --no-replicate-check disables this check,	but it also
	   disables immediate reporting	of checksum differences, thereby
	   requiring a second run of the tool with "--replicate-check-only" to
	   find	and print checksum differences.

PLUGIN
       The file	specified by "--plugin"	must define a class (i.e. a package)
       called "pt_table_checksum_plugin" with a	"new()"	subroutine.  The tool
       will create an instance of this class and call any hooks	that it
       defines.	 No hooks are required,	but a plugin isn't very	useful without
       them.

       These hooks, in this order, are called if defined:

	  init
	  before_replicate_check
	  after_replicate_check
	  get_slave_lag
	  before_checksum_table
	  after_checksum_table

       Each hook is passed different arguments.	 To see	which arguments	are
       passed to a hook, search	for the	hook's name in the tool's source code,
       like:

	  # --plugin hook
	  if ( $plugin && $plugin->can('init') ) {
	     $plugin->init(
		slaves	       => $slaves,
		slave_lag_cxns => $slave_lag_cxns,
		repl_table     => $repl_table,
	     );
	  }

       The comment "# --plugin hook" precedes every hook call.

       Please contact Percona if you have questions or need help.

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.

       o   A

	   dsn:	charset; copy: yes

	   Default character set.

       o   D

	   copy: no

	   DSN table database.

       o   F

	   dsn:	mysql_read_default_file; copy: yes

	   Defaults file for connection	values.

       o   h

	   dsn:	host; copy: yes

	   Connect to host.

       o   p

	   dsn:	password; copy:	yes

	   Password to use when	connecting.  If	password contains commas they
	   must	be escaped with	a backslash: "exam\,ple"

       o   P

	   dsn:	port; copy: yes

	   Port	number to use for connection.

       o   S

	   dsn:	mysql_socket; copy: no

	   Socket file to use for connection.

       o   t

	   copy: no

	   DSN table table.

       o   u

	   dsn:	user; copy: yes

	   User	for login if not current user.

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-table-checksum ... > 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-table-checksum>.

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

       o   Complete command-line used to run the tool

       o   Tool	"--version"

       o   MySQL version of all	servers	involved

       o   Output from the tool	including STDERR

       o   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 and Daniel Nichter

ACKNOWLEDGMENTS
       Claus Jeppesen, Francois	Saint-Jacques, Giuseppe	Maxia, Heikki Tuuri,
       James Briggs, Martin Friebe, and	Sergey Zhuravlev

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.

COPYRIGHT, LICENSE, AND	WARRANTY
       This program is copyright 2011-2016 Percona LLC and/or its affiliates,
       2007-2011 Baron Schwartz.

       THIS PROGRAM IS PROVIDED	"AS IS"	AND WITHOUT ANY	EXPRESS	OR IMPLIED
       WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
       MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

       This program is free software; you can redistribute it and/or modify it
       under the terms of the GNU General Public License as published by the
       Free Software Foundation, version 2; OR the Perl	Artistic License.  On
       UNIX and	similar	systems, you can issue `man perlgpl' or	`man
       perlartistic' to	read these licenses.

       You should have received	a copy of the GNU General Public License along
       with this program; if not, write	to the Free Software Foundation, Inc.,
       59 Temple Place,	Suite 330, Boston, MA  02111-1307  USA.

VERSION
       pt-table-checksum 2.2.17

perl v5.24.1			  2016-03-07		  PT-TABLE-CHECKSUM(1)

NAME | SYNOPSIS | RISKS | DESCRIPTION | LIMITATIONS | Percona XtraDB Cluster | OUTPUT | EXIT STATUS | OPTIONS | REPLICA CHECKS | PLUGIN | DSN OPTIONS | ENVIRONMENT | SYSTEM REQUIREMENTS | BUGS | DOWNLOADING | AUTHORS | ACKNOWLEDGMENTS | ABOUT PERCONA TOOLKIT | COPYRIGHT, LICENSE, AND WARRANTY | VERSION

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