Ubuntu Manpage: pt-query-digest - Analyze MySQL queries from logs, processlist, and tcpdump.

Provided by: percona-toolkit_3.1+dfsg-1.1_all

NAME

       pt-query-digest - Analyze MySQL queries from logs, processlist, and tcpdump.

SYNOPSIS

       Usage: pt-query-digest [OPTIONS] [FILES] [DSN]

       pt-query-digest analyzes MySQL queries from slow, general, and binary log files.  It can also analyze
       queries from "SHOW PROCESSLIST" and MySQL protocol data from tcpdump.  By default, queries are grouped by
       fingerprint and reported in descending order of query time (i.e. the slowest queries first).  If no
       "FILES" are given, the tool reads "STDIN".  The optional "DSN" is used for certain options like "--since"
       and "--until".

       Report the slowest queries from "slow.log":

          pt-query-digest slow.log

       Report the slowest queries from the processlist on host1:

          pt-query-digest --processlist h=host1

       Capture MySQL protocol data with tcppdump, then report the slowest queries:

          tcpdump -s 65535 -x -nn -q -tttt -i any -c 1000 port 3306 > mysql.tcp.txt

          pt-query-digest --type tcpdump mysql.tcp.txt

       Save query data from "slow.log" to host2 for later review and trend analysis:

          pt-query-digest --review h=host2 --no-report slow.log

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-query-digest is a sophisticated but easy to use tool for analyzing MySQL queries.  It can analyze
       queries from MySQL slow, general, and binary logs. (Binary logs must first be converted to text, see
       "--type").  It can also use "SHOW PROCESSLIST" and MySQL protocol data from tcpdump.  By default, the
       tool reports which queries are the slowest, and therefore the most important to optimize.  More complex
       and custom-tailored reports can be created by using options like "--group-by", "--filter", and
       "--embedded-attributes".

       Query analysis is a best-practice that should be done frequently.  To make this easier, pt-query-digest
       has two features: query review ("--review") and query history ("--history").  When the "--review" option
       is used, all unique queries are saved to a database.  When the tool is ran again with "--review", queries
       marked as reviewed in the database are not printed in the report.  This highlights new queries that need
       to be reviewed.  When the "--history" option is used, query metrics (query time, lock time, etc.) for
       each unique query are saved to database.  Each time the tool is ran with "--history", the more historical
       data is saved which can be used to trend and analyze query performance over time.

ATTRIBUTES

       pt-query-digest works on events, which are a collection of key-value pairs called attributes.  You'll
       recognize most of the attributes right away: "Query_time", "Lock_time", and so on.  You can just look at
       a slow log and see them.  However, there are some that don't exist in the slow log, and slow logs may
       actually include different kinds of attributes (for example, you may have a server with the Percona
       patches).

       See "ATTRIBUTES REFERENCE" near the end of this documentation for a list of common and "--type" specific
       attributes.  A familiarity with these attributes is necessary for working with "--filter",
       "--ignore-attributes", and other attribute-related options.

       With creative use of "--filter", you can create new attributes derived from existing attributes.  For
       example, to create an attribute called "Row_ratio" for examining the ratio of "Rows_sent" to
       "Rows_examined", specify a filter like:

         --filter '($event->{Row_ratio} = $event->{Rows_sent} / ($event->{Rows_examined})) && 1'

       The "&& 1" trick is needed to create a valid one-line syntax that is always true, even if the assignment
       happens to evaluate false.  The new attribute will automatically appears in the output:

         # Row ratio        1.00    0.00      1    0.50      1    0.71    0.50

       Attributes created this way can be specified for "--order-by" or any option that requires an attribute.

OUTPUT

       The default "--output" is a query analysis report.  The "--[no]report" option controls whether or not
       this report is printed.  Sometimes you may want to parse all the queries but suppress the report, for
       example when using "--review" or "--history".

       There is one paragraph for each class of query analyzed.  A "class" of queries all have the same value
       for the "--group-by" attribute which is "fingerprint" by default.  (See "ATTRIBUTES".)  A fingerprint is
       an abstracted version of the query text with literals removed, whitespace collapsed, and so forth.  The
       report is formatted so it's easy to paste into emails without wrapping, and all non-query lines begin
       with a comment, so you can save it to a .sql file and open it in your favorite syntax-highlighting text
       editor.  There is a response-time profile at the beginning.

       The output described here is controlled by "--report-format".  That option allows you to specify what to
       print and in what order.  The default output in the default order is described here.

       The report, by default, begins with a paragraph about the entire analysis run The information is very
       similar to what you'll see for each class of queries in the log, but it doesn't have some information
       that would be too expensive to keep globally for the analysis.  It also has some statistics about the
       code's execution itself, such as the CPU and memory usage, the local date and time of the run, and a list
       of input file read/parsed.

       Following this is the response-time profile over the events.  This is a highly summarized view of the
       unique events in the detailed query report that follows.  It contains the following columns:

        Column        Meaning
        ============  ==========================================================
        Rank          The query's rank within the entire set of queries analyzed
        Query ID      The query's fingerprint
        Response time The total response time, and percentage of overall total
        Calls         The number of times this query was executed
        R/Call        The mean response time per execution
        V/M           The Variance-to-mean ratio of response time
        Item          The distilled query

       A final line whose rank is shown as MISC contains aggregate statistics on the queries that were not
       included in the report, due to options such as "--limit" and "--outliers".  For details on the variance-
       to-mean ratio, please see http://en.wikipedia.org/wiki/Index_of_dispersion.

       Next, the detailed query report is printed.  Each query appears in a paragraph.  Here is a sample,
       slightly reformatted so 'perldoc' will not wrap lines in a terminal.  The following will all be one
       paragraph, but we'll break it up for commentary.

        # Query 2: 0.01 QPS, 0.02x conc, ID 0xFDEA8D2993C9CAF3 at byte 160665

       This line identifies the sequential number of the query in the sort order specified by "--order-by".
       Then there's the queries per second, and the approximate concurrency for this query (calculated as a
       function of the timespan and total Query_time).  Next there's a query ID.  This ID is a hex version of
       the query's checksum in the database, if you're using "--review".  You can select the reviewed query's
       details from the database with a query like "SELECT .... WHERE checksum=0xFDEA8D2993C9CAF3".

       If you are investigating the report and want to print out every sample of a particular query, then the
       following "--filter" may be helpful:

          pt-query-digest slow.log           \
             --no-report                     \
             --output slowlog                \
             --filter '$event->{fingerprint} \
                  && make_checksum($event->{fingerprint}) eq "FDEA8D2993C9CAF3"'

       Notice that you must remove the "0x" prefix from the checksum.

       Finally, in case you want to find a sample of the query in the log file, there's the byte offset where
       you can look.  (This is not always accurate, due to some anomalies in the slow log format, but it's
       usually right.)  The position refers to the worst sample, which we'll see more about below.

       Next is the table of metrics about this class of queries.

        #           pct   total    min    max     avg     95%  stddev  median
        # Count       0       2
        # Exec time  13   1105s   552s   554s    553s    554s      2s    553s
        # Lock time   0   216us   99us  117us   108us   117us    12us   108us
        # Rows sent  20   6.26M  3.13M  3.13M   3.13M   3.13M   12.73   3.13M
        # Rows exam   0   6.26M  3.13M  3.13M   3.13M   3.13M   12.73   3.13M

       The first line is column headers for the table.  The percentage is the percent of the total for the whole
       analysis run, and the total is the actual value of the specified metric.  For example, in this case we
       can see that the query executed 2 times, which is 13% of the total number of queries in the file.  The
       min, max and avg columns are self-explanatory.  The 95% column shows the 95th percentile; 95% of the
       values are less than or equal to this value.  The standard deviation shows you how tightly grouped the
       values are.  The standard deviation and median are both calculated from the 95th percentile, discarding
       the extremely large values.

       The stddev, median and 95th percentile statistics are approximate.  Exact statistics require keeping
       every value seen, sorting, and doing some calculations on them.  This uses a lot of memory.  To avoid
       this, we keep 1000 buckets, each of them 5% bigger than the one before, ranging from .000001 up to a very
       big number.  When we see a value we increment the bucket into which it falls.  Thus we have fixed memory
       per class of queries.  The drawback is the imprecision, which typically falls in the 5 percent range.

       Next we have statistics on the users, databases and time range for the query.

        # Users       1   user1
        # Databases   2     db1(1), db2(1)
        # Time range 2008-11-26 04:55:18 to 2008-11-27 00:15:15

       The users and databases are shown as a count of distinct values, followed by the values.  If there's only
       one, it's shown alone; if there are many, we show each of the most frequent ones, followed by the number
       of times it appears.

        # Query_time distribution
        #   1us
        #  10us
        # 100us
        #   1ms
        #  10ms  #####
        # 100ms  ####################
        #    1s  ##########
        #  10s+

       The execution times show a logarithmic chart of time clustering.  Each query goes into one of the
       "buckets" and is counted up.  The buckets are powers of ten.  The first bucket is all values in the
       "single microsecond range" -- that is, less than 10us.  The second is "tens of microseconds," which is
       from 10us up to (but not including) 100us; and so on.  The charted attribute can be changed by specifying
       "--report-histogram" but is limited to time-based attributes.

        # Tables
        #    SHOW TABLE STATUS LIKE 'table1'\G
        #    SHOW CREATE TABLE `table1`\G
        # EXPLAIN
        SELECT * FROM table1\G

       This section is a convenience: if you're trying to optimize the queries you see in the slow log, you
       probably want to examine the table structure and size.  These are copy-and-paste-ready commands to do
       that.

       Finally, we see a sample of the queries in this class of query.  This is not a random sample.  It is the
       query that performed the worst, according to the sort order given by "--order-by".  You will normally see
       a commented "# EXPLAIN" line just before it, so you can copy-paste the query to examine its EXPLAIN plan.
       But for non-SELECT queries that isn't possible to do, so the tool tries to transform the query into a
       roughly equivalent SELECT query, and adds that below.

       If you want to find this sample event in the log, use the offset mentioned above, and something like the
       following:

         tail -c +<offset> /path/to/file | head

       See also "--report-format".

QUERY REVIEW

A query "--review" is the process of storing all the query fingerprints analyzed. This has several
benefits:

• You can add metadata to classes of queries, such as marking them for follow-up, adding notes to
queries, or marking them with an issue ID for your issue tracking system.

• You can refer to the stored values on subsequent runs so you'll know whether you've seen a query
before. This can help you cut down on duplicated work.

• You can store historical data such as the row count, query times, and generally anything you can see
in the report.

To use this feature, you run pt-query-digest with the "--review" option. It will store the fingerprints
and other information into the table you specify. Next time you run it with the same option, it will do
the following:

• It won't show you queries you've already reviewed. A query is considered to be already reviewed if
you've set a value for the "reviewed_by" column. (If you want to see queries you've already
reviewed, use the "--report-all" option.)

• Queries that you've reviewed, and don't appear in the output, will cause gaps in the query number
sequence in the first line of each paragraph. And the value you've specified for "--limit" will
still be honored. So if you've reviewed all queries in the top 10 and you ask for the top 10, you
won't see anything in the output.

• If you want to see the queries you've already reviewed, you can specify "--report-all". Then you'll
see the normal analysis output, but you'll also see the information from the review table, just below
the execution time graph. For example,

# Review information
# comments: really bad IN() subquery, fix soon!
# first_seen: 2008-12-01 11:48:57
# jira_ticket: 1933
# last_seen: 2008-12-18 11:49:07
# priority: high
# reviewed_by: xaprb
# reviewed_on: 2008-12-18 15:03:11

This metadata is useful because, as you analyze your queries, you get your comments integrated right
into the report.

FINGERPRINTS

       A query fingerprint is the abstracted form of a query, which makes it possible to group similar queries
       together.  Abstracting a query removes literal values, normalizes whitespace, and so on.  For example,
       consider these two queries:

         SELECT name, password FROM user WHERE id='12823';
         select name,   password from user
            where id=5;

       Both of those queries will fingerprint to

         select name, password from user where id=?

       Once the query's fingerprint is known, we can then talk about a query as though it represents all similar
       queries.

       What "pt-query-digest" does is analogous to a GROUP BY statement in SQL.  (But note that "multiple
       columns" doesn't define a multi-column grouping; it defines multiple reports!) If your command-line looks
       like this,

         pt-query-digest               \
             --group-by fingerprint    \
             --order-by Query_time:sum \
             --limit 10                \
             slow.log

       The corresponding pseudo-SQL looks like this:

         SELECT WORST(query BY Query_time), SUM(Query_time), ...
         FROM /path/to/slow.log
         GROUP BY FINGERPRINT(query)
         ORDER BY SUM(Query_time) DESC
         LIMIT 10

       You can also use the value "distill", which is a kind of super-fingerprint.  See "--group-by" for more.

       Query fingerprinting accommodates many special cases, which have proven necessary in the real world.  For
       example, an "IN" list with 5 literals is really equivalent to one with 4 literals, so lists of literals
       are collapsed to a single one.  If you find something that is not fingerprinted properly, please submit a
       bug report with a reproducible test case.

       Here is a list of transformations during fingerprinting, which might not be exhaustive:

       •   Group all SELECT queries from mysqldump together, even if they are against different tables.  The
           same applies to all queries from pt-table-checksum.

       •   Shorten multi-value INSERT statements to a single VALUES() list.

       •   Strip comments.

       •   Abstract the databases in USE statements, so all USE statements are grouped together.

       •   Replace all literals, such as quoted strings.  For efficiency, the code that replaces literal numbers
           is somewhat non-selective, and might replace some things as numbers when they really are not.
           Hexadecimal literals are also replaced.  NULL is treated as a literal.  Numbers embedded in
           identifiers are also replaced, so tables named similarly will be fingerprinted to the same values
           (e.g. users_2009 and users_2010 will fingerprint identically).

       •   Collapse all whitespace into a single space.

       •   Lowercase the entire query.

       •   Replace all literals inside of IN() and VALUES() lists with a single placeholder, regardless of
           cardinality.

       •   Collapse multiple identical UNION queries into a single one.

OPTIONS

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

--ask-pass
Prompt for a password when connecting to MySQL.

--attribute-aliases
type: array; default: db|Schema

List of attribute|alias,etc.

Certain attributes have multiple names, like db and Schema. If an event does not have the primary
attribute, pt-query-digest looks for an alias attribute. If it finds an alias, it creates the
primary attribute with the alias attribute's value and removes the alias attribute.

If the event has the primary attribute, all alias attributes are deleted.

This helps simplify event attributes so that, for example, there will not be report lines for both db
and Schema.

--attribute-value-limit
type: int; default: 0

A sanity limit for attribute values.

This option deals with bugs in slow logging functionality that causes large values for attributes.
If the attribute's value is bigger than this, the last-seen value for that class of query is used
instead. Disabled by default.

--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.

--config
type: Array

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

--[no]continue-on-error
default: yes

Continue parsing even if there is an error. The tool will not continue forever: it stops once any
process causes 100 errors, in which case there is probably a bug in the tool or the input is invalid.

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

Create the "--history" table if it does not exist.

This option causes the table specified by "--history" to be created with the default structure shown
in the documentation for "--history".

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

Create the "--review" table if it does not exist.

This option causes the table specified by "--review" to be created with the default structure shown
in the documentation for "--review".

--daemonize
Fork to the background and detach from the shell. POSIX operating systems only.

--database
short form: -D; type: string

Connect to this database.

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

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

--embedded-attributes
type: array

Two Perl regex patterns to capture pseudo-attributes embedded in queries.

Embedded attributes might be special attribute-value pairs that you've hidden in comments. The first
regex should match the entire set of attributes (in case there are multiple). The second regex
should match and capture attribute-value pairs from the first regex.

For example, suppose your query looks like the following:

SELECT * from users -- file: /login.php, line: 493;

You might run pt-query-digest with the following option:

pt-query-digest --embedded-attributes ' -- .*','(\w+): ([^\,]+)'

The first regular expression captures the whole comment:

" -- file: /login.php, line: 493;"

The second one splits it into attribute-value pairs and adds them to the event:

ATTRIBUTE VALUE
========= ==========
file /login.php
line 493

NOTE: All commas in the regex patterns must be escaped with \ otherwise the pattern will break.

--expected-range
type: array; default: 5,10

Explain items when there are more or fewer than expected.

Defines the number of items expected to be seen in the report given by "--[no]report", as controlled
by "--limit" and "--outliers". If there are more or fewer items in the report, each one will
explain why it was included.

--explain
type: DSN

Run EXPLAIN for the sample query with this DSN and print results.

This works only when "--group-by" includes fingerprint. It causes pt-query-digest to run EXPLAIN and
include the output into the report. For safety, queries that appear to have a subquery that EXPLAIN
will execute won't be EXPLAINed. Those are typically "derived table" queries of the form

select ... from ( select .... ) der;

The EXPLAIN results are printed as a full vertical format in the event report, which appears at the
end of each event report in vertical style ("\G") just like MySQL prints it.

--filter
type: string

Discard events for which this Perl code doesn't return true.

This option is a string of Perl code or a file containing Perl code that gets compiled into a
subroutine with one argument: $event. This is a hashref. If the given value is a readable file,
then pt-query-digest reads the entire file and uses its contents as the code. The file should not
contain a shebang (#!/usr/bin/perl) line.

If the code returns true, the chain of callbacks continues; otherwise it ends. The code is the last
statement in the subroutine other than "return $event". The subroutine template is:

sub { $event = shift; filter && return $event; }

Filters given on the command line are wrapped inside parentheses like like "( filter )". For
complex, multi-line filters, you must put the code inside a file so it will not be wrapped inside
parentheses. Either way, the filter must produce syntactically valid code given the template. For
example, an if-else branch given on the command line would not be valid:

--filter 'if () { } else { }' # WRONG

Since it's given on the command line, the if-else branch would be wrapped inside parentheses which is
not syntactically valid. So to accomplish something more complex like this would require putting the
code in a file, for example filter.txt:

my $event_ok; if (...) { $event_ok=1; } else { $event_ok=0; } $event_ok

Then specify "--filter filter.txt" to read the code from filter.txt.

If the filter code won't compile, pt-query-digest will die with an error. If the filter code does
compile, an error may still occur at runtime if the code tries to do something wrong (like pattern
match an undefined value). pt-query-digest does not provide any safeguards so code carefully!

An example filter that discards everything but SELECT statements:

--filter '$event->{arg} =~ m/^select/i'

This is compiled into a subroutine like the following:

sub { $event = shift; ( $event->{arg} =~ m/^select/i ) && return $event; }

It is permissible for the code to have side effects (to alter $event).

See "ATTRIBUTES REFERENCE" for a list of common and "--type" specific attributes.

Here are more examples of filter code:

Host/IP matches domain.com
--filter '($event->{host} || $event->{ip} || "") =~ m/domain.com/'

Sometimes MySQL logs the host where the IP is expected. Therefore, we check both.

User matches john
--filter '($event->{user} || "") =~ m/john/'

More than 1 warning
--filter '($event->{Warning_count} || 0) > 1'

Query does full table scan or full join
--filter '(($event->{Full_scan} || "") eq "Yes") || (($event->{Full_join} || "") eq "Yes")'

Query was not served from query cache
--filter '($event->{QC_Hit} || "") eq "No"'

Query is 1 MB or larger
--filter '$event->{bytes} >= 1_048_576'

Since "--filter" allows you to alter $event, you can use it to do other things, like create new
attributes. See "ATTRIBUTES" for an example.

--group-by
type: Array; default: fingerprint

Which attribute of the events to group by.

In general, you can group queries into classes based on any attribute of the query, such as "user" or
"db", which will by default show you which users and which databases get the most "Query_time". The
default attribute, "fingerprint", groups similar, abstracted queries into classes; see below and see
also "FINGERPRINTS".

A report is printed for each "--group-by" value (unless "--no-report" is given). Therefore,
"--group-by user,db" means "report on queries with the same user and report on queries with the same
db"; it does not mean "report on queries with the same user and db." See also "OUTPUT".

Every value must have a corresponding value in the same position in "--order-by". However, adding
values to "--group-by" will automatically add values to "--order-by", for your convenience.

There are several magical values that cause some extra data mining to happen before the grouping
takes place:

fingerprint
This causes events to be fingerprinted to abstract queries into a canonical form, which is then
used to group events together into a class. See "FINGERPRINTS" for more about fingerprinting.

tables
This causes events to be inspected for what appear to be tables, and then aggregated by that.
Note that a query that contains two or more tables will be counted as many times as there are
tables; so a join against two tables will count the Query_time against both tables.

distill
This is a sort of super-fingerprint that collapses queries down into a suggestion of what they
do, such as "INSERT SELECT table1 table2".

--help
Show help and exit.

--history
type: DSN

Save metrics for each query class in the given table. pt-query-digest saves query metrics (query
time, lock time, etc.) to this table so you can see how query classes change over time.

The default table is "percona_schema.query_history". Specify database (D) and table (t) DSN options
to override the default. The database and table are automatically created unless
"--no-create-history-table" is specified (see "--[no]create-history-table").

pt-query-digest inspects the columns in the table. The table must have at least the following
columns:

CREATE TABLE query_review_history (
checksum CHAR(32) NOT NULL,
sample TEXT NOT NULL
);

Any columns not mentioned above are inspected to see if they follow a certain naming convention. The
column is special if the name ends with an underscore followed by any of these values:

pct|avg|cnt|sum|min|max|pct_95|stddev|median|rank

If the column ends with one of those values, then the prefix is interpreted as the event attribute to
store in that column, and the suffix is interpreted as the metric to be stored. For example, a
column named "Query_time_min" will be used to store the minimum "Query_time" for the class of events.

The table should also have a primary key, but that is up to you, depending on how you want to store
the historical data. We suggest adding ts_min and ts_max columns and making them part of the primary
key along with the checksum. But you could also just add a ts_min column and make it a DATE type, so
you'd get one row per class of queries per day.

The following table definition is used for "--[no]create-history-table":

CREATE TABLE IF NOT EXISTS query_history (
checksum CHAR(32) NOT NULL,
sample TEXT NOT NULL,
ts_min DATETIME,
ts_max DATETIME,
ts_cnt FLOAT,
Query_time_sum FLOAT,
Query_time_min FLOAT,
Query_time_max FLOAT,
Query_time_pct_95 FLOAT,
Query_time_stddev FLOAT,
Query_time_median FLOAT,
Lock_time_sum FLOAT,
Lock_time_min FLOAT,
Lock_time_max FLOAT,
Lock_time_pct_95 FLOAT,
Lock_time_stddev FLOAT,
Lock_time_median FLOAT,
Rows_sent_sum FLOAT,
Rows_sent_min FLOAT,
Rows_sent_max FLOAT,
Rows_sent_pct_95 FLOAT,
Rows_sent_stddev FLOAT,
Rows_sent_median FLOAT,
Rows_examined_sum FLOAT,
Rows_examined_min FLOAT,
Rows_examined_max FLOAT,
Rows_examined_pct_95 FLOAT,
Rows_examined_stddev FLOAT,
Rows_examined_median FLOAT,
-- Percona extended slowlog attributes
-- http://www.percona.com/docs/wiki/patches:slow_extended
Rows_affected_sum FLOAT,
Rows_affected_min FLOAT,
Rows_affected_max FLOAT,
Rows_affected_pct_95 FLOAT,
Rows_affected_stddev FLOAT,
Rows_affected_median FLOAT,
Rows_read_sum FLOAT,
Rows_read_min FLOAT,
Rows_read_max FLOAT,
Rows_read_pct_95 FLOAT,
Rows_read_stddev FLOAT,
Rows_read_median FLOAT,
Merge_passes_sum FLOAT,
Merge_passes_min FLOAT,
Merge_passes_max FLOAT,
Merge_passes_pct_95 FLOAT,
Merge_passes_stddev FLOAT,
Merge_passes_median FLOAT,
InnoDB_IO_r_ops_min FLOAT,
InnoDB_IO_r_ops_max FLOAT,
InnoDB_IO_r_ops_pct_95 FLOAT,
InnoDB_IO_r_ops_stddev FLOAT,
InnoDB_IO_r_ops_median FLOAT,
InnoDB_IO_r_bytes_min FLOAT,
InnoDB_IO_r_bytes_max FLOAT,
InnoDB_IO_r_bytes_pct_95 FLOAT,
InnoDB_IO_r_bytes_stddev FLOAT,
InnoDB_IO_r_bytes_median FLOAT,
InnoDB_IO_r_wait_min FLOAT,
InnoDB_IO_r_wait_max FLOAT,
InnoDB_IO_r_wait_pct_95 FLOAT,
InnoDB_IO_r_wait_stddev FLOAT,
InnoDB_IO_r_wait_median FLOAT,
InnoDB_rec_lock_wait_min FLOAT,
InnoDB_rec_lock_wait_max FLOAT,
InnoDB_rec_lock_wait_pct_95 FLOAT,
InnoDB_rec_lock_wait_stddev FLOAT,
InnoDB_rec_lock_wait_median FLOAT,
InnoDB_queue_wait_min FLOAT,
InnoDB_queue_wait_max FLOAT,
InnoDB_queue_wait_pct_95 FLOAT,
InnoDB_queue_wait_stddev FLOAT,
InnoDB_queue_wait_median FLOAT,
InnoDB_pages_distinct_min FLOAT,
InnoDB_pages_distinct_max FLOAT,
InnoDB_pages_distinct_pct_95 FLOAT,
InnoDB_pages_distinct_stddev FLOAT,
InnoDB_pages_distinct_median FLOAT,
-- Boolean (Yes/No) attributes. Only the cnt and sum are needed
-- for these. cnt is how many times is attribute was recorded,
-- and sum is how many of those times the value was Yes. So
-- sum/cnt * 100 equals the percentage of recorded times that
-- the value was Yes.
QC_Hit_cnt FLOAT,
QC_Hit_sum FLOAT,
Full_scan_cnt FLOAT,
Full_scan_sum FLOAT,
Full_join_cnt FLOAT,
Full_join_sum FLOAT,
Tmp_table_cnt FLOAT,
Tmp_table_sum FLOAT,
Tmp_table_on_disk_cnt FLOAT,
Tmp_table_on_disk_sum FLOAT,
Filesort_cnt FLOAT,
Filesort_sum FLOAT,
Filesort_on_disk_cnt FLOAT,
Filesort_on_disk_sum FLOAT,
PRIMARY KEY(checksum, ts_min, ts_max)
);

Note that we store the count (cnt) for the ts attribute only; it will be redundant to store this for
other attributes.

Starting from Percona Toolkit 3.0.11, the checksum function has been updated to use 32 chars in the
MD5 sum. This causes the checksum field in the history table will have a different value than in the
previous versions of the tool.

--host
short form: -h; type: string

Connect to host.

--ignore-attributes
type: array; default: arg, cmd, insert_id, ip, port, Thread_id, timestamp, exptime, flags, key, res,
val, server_id, offset, end_log_pos, Xid

Do not aggregate these attributes. Some attributes are not query metrics but metadata which doesn't
need to be (or can't be) aggregated.

--inherit-attributes
type: array; default: db,ts

If missing, inherit these attributes from the last event that had them.

This option sets which attributes are inherited or carried forward to events which do not have them.
For example, if one event has the db attribute equal to "foo", but the next event doesn't have the db
attribute, then it inherits "foo" for its db attribute.

--interval
type: float; default: .1

How frequently to poll the processlist, in seconds.

--iterations
type: int; default: 1

How many times to iterate through the collect-and-report cycle. If 0, iterate to infinity. Each
iteration runs for "--run-time" amount of time. An iteration is usually determined by an amount of
time and a report is printed when that amount of time elapses. With "--run-time-mode" "interval", an
interval is instead determined by the interval time you specify with "--run-time". See "--run-time"
and "--run-time-mode" for more information.

--limit
type: Array; default: 95%:20

Limit output to the given percentage or count.

If the argument is an integer, report only the top N worst queries. If the argument is an integer
followed by the "%" sign, report that percentage of the worst queries. If the percentage is followed
by a colon and another integer, report the top percentage or the number specified by that integer,
whichever comes first.

The value is actually a comma-separated array of values, one for each item in "--group-by". If you
don't specify a value for any of those items, the default is the top 95%.

See also "--outliers".

--log
type: string

Print all output to this file when daemonized.

--max-hostname-length
type: int; default: 10

Trim host names in reports to this length. 0=Do not trim host names.

--max-line-length
type: int; default: 74

Trim lines to this length. 0=Do not trim lines.

--order-by
type: Array; default: Query_time:sum

Sort events by this attribute and aggregate function.

This is a comma-separated list of order-by expressions, one for each "--group-by" attribute. The
default "Query_time:sum" is used for "--group-by" attributes without explicitly given "--order-by"
attributes (that is, if you specify more "--group-by" attributes than corresponding "--order-by"
attributes). The syntax is "attribute:aggregate". See "ATTRIBUTES" for valid attributes. Valid
aggregates are:

Aggregate Meaning
========= ============================
sum Sum/total attribute value
min Minimum attribute value
max Maximum attribute value
cnt Frequency/count of the query

For example, the default "Query_time:sum" means that queries in the query analysis report will be
ordered (sorted) by their total query execution time ("Exec time"). "Query_time:max" orders the
queries by their maximum query execution time, so the query with the single largest "Query_time" will
be list first. "cnt" refers more to the frequency of the query as a whole, how often it appears;
"Count" is its corresponding line in the query analysis report. So any attribute and "cnt" should
yield the same report wherein queries are sorted by the number of times they appear.

When parsing general logs ("--type" "genlog"), the default "--order-by" becomes "Query_time:cnt".
General logs do not report query times so only the "cnt" aggregate makes sense because all query
times are zero.

If you specify an attribute that doesn't exist in the events, then pt-query-digest falls back to the
default "Query_time:sum" and prints a notice at the beginning of the report for each query class.
You can create attributes with "--filter" and order by them; see "ATTRIBUTES" for an example.

--outliers
type: array; default: Query_time:1:10

Report outliers by attribute:percentile:count.

The syntax of this option is a comma-separated list of colon-delimited strings. The first field is
the attribute by which an outlier is defined. The second is a number that is compared to the
attribute's 95th percentile. The third is optional, and is compared to the attribute's cnt
aggregate. Queries that pass this specification are added to the report, regardless of any limits
you specified in "--limit".

For example, to report queries whose 95th percentile Query_time is at least 60 seconds and which are
seen at least 5 times, use the following argument:

--outliers Query_time:60:5

You can specify an --outliers option for each value in "--group-by".

--output
type: string; default: report

How to format and print the query analysis results. Accepted values are:

VALUE FORMAT
======= ==============================
report Standard query analysis report
slowlog MySQL slow log
json JSON, on array per query class
json-anon JSON without example queries
secure-slowlog JSON without example queries

The entire "report" output can be disabled by specifying "--no-report" (see "--[no]report"), and its
sections can be disabled or rearranged by specifying "--report-format".

"json" output was introduced in 2.2.1 and is still in development, so the data structure may change
in future versions.

--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.

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

Port number to use for connection.

--preserve-embedded-numbers
Preserve numbers in database/table names when fingerprinting queries. The standard fingeprint method
replaces numbers in db/tables names, making a query like 'SELECT * FROM db1.table2' to be
figerprinted as 'SELECT * FROM db?.table?'. This option changes that behaviour and the fingerprint
will become 'SELECT * FROM db1.table2'.

--processlist
type: DSN

Poll this DSN's processlist for queries, with "--interval" sleep between.

If the connection fails, pt-query-digest tries to reopen it once per second.

--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.

--read-timeout
type: time; default: 0

Wait this long for an event from the input; 0 to wait forever.

This option sets the maximum time to wait for an event from the input. It applies to all types of
input except "--processlist". If an event is not received after the specified time, the script stops
reading the input and prints its reports. If "--iterations" is 0 or greater than 1, the next
iteration will begin, else the script will exit.

This option requires the Perl POSIX module.

--[no]report
default: yes

Print query analysis reports for each "--group-by" attribute. This is the standard slow log analysis
functionality. See "OUTPUT" for the description of what this does and what the results look like.

If you don't need a report (for example, when using "--review" or "--history"), it is best to specify
"--no-report" because this allows the tool to skip some expensive operations.

--report-all
Report all queries, even ones that have been reviewed. This only affects the "report" "--output"
when using "--review". Otherwise, all queries are always printed.

--report-format
type: Array; default: rusage,date,hostname,files,header,profile,query_report,prepared

Print these sections of the query analysis report.

SECTION PRINTS
============ ======================================================
rusage CPU times and memory usage reported by ps
date Current local date and time
hostname Hostname of machine on which pt-query-digest was run
files Input files read/parse
header Summary of the entire analysis run
profile Compact table of queries for an overview of the report
query_report Detailed information about each unique query
prepared Prepared statements

The sections are printed in the order specified. The rusage, date, files and header sections are
grouped together if specified together; other sections are separated by blank lines.

See "OUTPUT" for more information on the various parts of the query report.

--report-histogram
type: string; default: Query_time

Chart the distribution of this attribute's values.

The distribution chart is limited to time-based attributes, so charting "Rows_examined", for example,
will produce a useless chart. Charts look like:

# Query_time distribution
# 1us
# 10us
# 100us
# 1ms
# 10ms ###########################
# 100ms ########################################################
# 1s ########
# 10s+

See "OUTPUT" for more information.

--resume
type: string

If specified, the tool writes the last file offset, if there is one, to the given filename. When ran
again with the same value for this option, the tool reads the last file offset from the file, seeks
to that position in the log, and resumes parsing events from that point onward.

--review
type: DSN

Save query classes for later review, and don't report already reviewed classes.

The default table is "percona_schema.query_review". Specify database (D) and table (t) DSN options
to override the default. The database and table are automatically created unless
"--no-create-review-table" is specified (see "--[no]create-review-table").

If the table was created manually, it must have at least the following columns. You can add more
columns for your own special purposes, but they won't be used by pt-query-digest.

CREATE TABLE IF NOT EXISTS query_review (
checksum CHAR(32) NOT NULL PRIMARY KEY,
fingerprint TEXT NOT NULL,
sample TEXT NOT NULL,
first_seen DATETIME,
last_seen DATETIME,
reviewed_by VARCHAR(20),
reviewed_on DATETIME,
comments TEXT
)

The columns are:

COLUMN MEANING
=========== ====================================================
checksum A 64-bit checksum of the query fingerprint
fingerprint The abstracted version of the query; its primary key
sample The query text of a sample of the class of queries
first_seen The smallest timestamp of this class of queries
last_seen The largest timestamp of this class of queries
reviewed_by Initially NULL; if set, query is skipped thereafter
reviewed_on Initially NULL; not assigned any special meaning
comments Initially NULL; not assigned any special meaning

Note that the "fingerprint" column is the true primary key for a class of queries. The "checksum" is
just a cryptographic hash of this value, which provides a shorter value that is very likely to also
be unique.

After parsing and aggregating events, your table should contain a row for each fingerprint. This
option depends on "--group-by fingerprint" (which is the default). It will not work otherwise.

--run-time
type: time

How long to run for each "--iterations". The default is to run forever (you can interrupt with CTRL-
C). Because "--iterations" defaults to 1, if you only specify "--run-time", pt-query-digest runs for
that amount of time and then exits. The two options are specified together to do collect-and-report
cycles. For example, specifying "--iterations" 4 "--run-time" "15m" with a continuous input (like
STDIN or "--processlist") will cause pt-query-digest to run for 1 hour (15 minutes x 4), reporting
four times, once at each 15 minute interval.

--run-time-mode
type: string; default: clock

Set what the value of "--run-time" operates on. Following are the possible values for this option:

clock
"--run-time" specifies an amount of real clock time during which the tool should run for each
"--iterations".

event
"--run-time" specifies an amount of log time. Log time is determined by timestamps in the log.
The first timestamp seen is remembered, and each timestamp after that is compared to the first to
determine how much log time has passed. For example, if the first timestamp seen is "12:00:00"
and the next is "12:01:30", that is 1 minute and 30 seconds of log time. The tool will read
events until the log time is greater than or equal to the specified "--run-time" value.

Since timestamps in logs are not always printed, or not always printed frequently, this mode
varies in accuracy.

interval
"--run-time" specifies interval boundaries of log time into which events are divided and reports
are generated. This mode is different from the others because it doesn't specify how long to
run. The value of "--run-time" must be an interval that divides evenly into minutes, hours or
days. For example, "5m" divides evenly into hours (60/5=12, so 12 5 minutes intervals per hour)
but "7m" does not (60/7=8.6).

Specifying "--run-time-mode interval --run-time 30m --iterations 0" is similar to specifying
"--run-time-mode clock --run-time 30m --iterations 0". In the latter case, pt-query-digest will
run forever, producing reports every 30 minutes, but this only works effectively with continuous
inputs like STDIN and the processlist. For fixed inputs, like log files, the former example
produces multiple reports by dividing the log into 30 minutes intervals based on timestamps.

Intervals are calculated from the zeroth second/minute/hour in which a timestamp occurs, not from
whatever time it specifies. For example, with 30 minute intervals and a timestamp of "12:10:30",
the interval is not "12:10:30" to "12:40:30", it is "12:00:00" to "12:29:59". Or, with 1 hour
intervals, it is "12:00:00" to "12:59:59". When a new timestamp exceeds the interval, a report
is printed, and the next interval is recalculated based on the new timestamp.

Since "--iterations" is 1 by default, you probably want to specify a new value else pt-query-
digest will only get and report on the first interval from the log since 1 interval = 1
iteration. If you want to get and report every interval in a log, specify "--iterations" 0.

--sample
type: int

Filter out all but the first N occurrences of each query. The queries are filtered on the first
value in "--group-by", so by default, this will filter by query fingerprint. For example, "--sample
2" will permit two sample queries for each fingerprint. Useful in conjunction with "--output
slowlog" to print the queries. You probably want to set "--no-report" to avoid the overhead of
aggregating and reporting if you're just using this to print out samples of queries. A complete
example:

pt-query-digest --sample 2 --no-report --output slowlog slow.log

--slave-user
type: string

Sets the user to be used to connect to the slaves. This parameter allows you to have a different
user with less privileges on the slaves but that user must exist on all slaves.

--slave-password
type: string

Sets the password to be used to connect to the slaves. It can be used with --slave-user and the
password for the user must be the same on all slaves.

--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 defaultvalue of 10000.

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

--show-all
type: Hash

Show all values for these attributes.

By default pt-query-digest only shows as many of an attribute's value that fit on a single line.
This option allows you to specify attributes for which all values will be shown (line width is
ignored). This only works for attributes with string values like user, host, db, etc. Multiple
attributes can be specified, comma-separated.

--since
type: string

Parse only queries newer than this value (parse queries since this date).

This option allows you to ignore queries older than a certain value and parse only those queries
which are more recent than the value. The value can be several types:

* Simple time value N with optional suffix: N[shmd], where
s=seconds, h=hours, m=minutes, d=days (default s if no suffix
given); this is like saying "since N[shmd] ago"
* Full date with optional hours:minutes:seconds:
YYYY-MM-DD [HH:MM:SS]
* Short, MySQL-style date:
YYMMDD [HH:MM:SS]
* Any time expression evaluated by MySQL:
CURRENT_DATE - INTERVAL 7 DAY

If you give a MySQL time expression, and you have not also specified a DSN for "--explain",
"--processlist", or "--review", then you must specify a DSN on the command line so that pt-query-
digest can connect to MySQL to evaluate the expression.

The MySQL time expression is wrapped inside a query like "SELECT UNIX_TIMESTAMP(<expression>)", so be
sure that the expression is valid inside this query. For example, do not use UNIX_TIMESTAMP()
because UNIX_TIMESTAMP(UNIX_TIMESTAMP()) returns 0.

Events are assumed to be in chronological: older events at the beginning of the log and newer events
at the end of the log. "--since" is strict: it ignores all queries until one is found that is new
enough. Therefore, if the query events are not consistently timestamped, some may be ignored which
are actually new enough.

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

           dsn: charset; copy: yes

           Default character set.

       •   D

           dsn: database; copy: yes

           Default database to use when connecting to MySQL.

       •   F

           dsn: mysql_read_default_file; copy: yes

           Only read default options from the given file.

       •   h

           dsn: host; copy: yes

           Connect to host.

       •   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

           The "--review" or "--history" table.

       •   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-query-digest ... > 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-query-digest>.

       Please report bugs at <https://jira.percona.com/projects/PT>.  Include the following information in your
       bug report:

       •   Complete command-line used to run the tool

       •   Tool "--version"

       •   MySQL version of all servers involved

       •   Output from the tool including STDERR

       •   Input files (log/dump/config files, etc.)

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

DOWNLOADING

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

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

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

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

       You can also get individual tools from the latest release:

          wget percona.com/get/TOOL

       Replace "TOOL" with the name of any tool.

ATTRIBUTES REFERENCE

Events may have the following attributes. If writing a "--filter", be sure to check that an attribute is
defined in each event before using it, else the filter code may crash the tool with a "use of
uninitialized value" error.

You can dump event attributes for any input like:

$ pt-query-digest \
slow.log \
--filter 'print Dumper $event' \
--no-report \
--sample 1

That will produce a lot of output with "attribute => value" pairs like:

$VAR1 = {
Query_time => '0.033384',
Rows_examined => '0',
Rows_sent => '0',
Thread_id => '10',
Tmp_table => 'No',
Tmp_table_on_disk => 'No',
arg => 'SELECT col FROM tbl WHERE id=5',
bytes => 103,
cmd => 'Query',
db => 'db1',
fingerprint => 'select col from tbl where id=?',
host => '',
pos_in_log => 1334,
ts => '071218 11:48:27',
user => '[SQL_SLAVE]'
};

COMMON
These attribute are common to all input "--type" and "--processlist", except where noted.

arg The query text, or the command for admin commands like "Ping".

bytes
The byte length of the "arg".

cmd "Query" or "Admin".

db The current database. The value comes from USE database statements. By default, "Schema" is an
alias which is automatically changed to "db"; see "--attribute-aliases".

fingerprint
An abstracted form of the query. See "FINGERPRINTS".

host
Client host which executed the query.

pos_in_log
The byte offset of the event in the log or tcpdump, except for "--processlist".

Query_time
The total time the query took, including lock time.

ts The timestamp of when the query ended.

SLOW, GENERAL, AND BINARY LOGS
Events have all available attributes from the log file. Therefore, you only need to look at the log file
to see which events are available, but remember: not all events have the same attributes.

Percona Server adds many attributes to the slow log; see
http://www.percona.com/docs/wiki/patches:slow_extended for more information.

TCPDUMP
These attributes are available when parsing "--type" tcpdump.

Error_no
The MySQL error number if the query caused an error.

ip The client's IP address. Certain log files may also contain this attribute.

No_good_index_used
Yes or No if no good index existed for the query (flag set by server).

No_index_used
Yes or No if the query did not use any index (flag set by server).

port
The client's port number.

Warning_count
The number of warnings, as otherwise shown by "SHOW WARNINGS".

PROCESSLIST
If using "--processlist", an "id" attribute is available for the process ID, in addition to the common
attributes.

AUTHORS

       Baron Schwartz, Daniel Nichter, and Brian Fraser

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 2008-2018 Percona LLC and/or its affiliates.

       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-query-digest 3.1.0

POD ERRORS

       Hey! The above document had some coding errors, which are explained below:

       Around line 16595:
           Non-ASCII character seen before =encoding in 'Percona’s'. Assuming UTF-8