pt-fingerprint - Convert queries into fingerprints.
pt-fingerprint [OPTIONS] [FILES]
pt-fingerprint converts queries into fingerprints. With the –query option, converts the option’s value into a fingerprint. With no options, treats command-line arguments as FILEs and reads and converts semicolon-separated queries from the FILEs. When FILE is -, it read standard input.
Convert a single query:
pt-fingerprint --query "select a, b, c from users where id = 500"
Convert a file full of queries:
The following section is included to inform users about the potential risks, whether known or unknown, of using this tool. The two main categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.
The pt-fingerprint tool simply reads data and transforms it, so risks are minimal.
See also “BUGS” for more information on filing bugs and getting help.
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.
Query fingerprinting accommodates a great 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 want to understand more about how and why all of these cases are handled, please review the test cases in the Subversion repository. 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. Ditto for all of pt-table-checksum’s checksum queries.
- 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.
This tool accepts additional command-line arguments. Refer to the “SYNOPSIS” and usage information for details.
Read this comma-separated list of config files; if specified, this must be the first option on the command line.
Show help and exit.
Match numbers embedded in words and replace as single values. This option causes the tool to be more careful about matching numbers so that words with numbers, like catch22 are matched and replaced as a single ? placeholder. Otherwise the default number matching pattern will replace catch22 as catch?.
This is helpful if database or table names contain numbers.
Match MD5 checksums and replace as single values. This option causes the tool to be more careful about matching numbers so that MD5 checksums like fbc5e685a5d3d45aa1d0347fdb7c4d35 are matched and replaced as a single ? placeholder. Otherwise, the default number matching pattern will replace fbc5e685a5d3d45aa1d0347fdb7c4d35 as fbc?.
The query to convert into a fingerprint.
Show version and exit.
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-fingerprint ... > FILE 2>&1
Be careful: debugging output is voluminous and can generate several megabytes of output.
You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.
For a list of known bugs, see http://www.percona.com/bugs/pt-fingerprint.
Please report bugs at https://bugs.launchpad.net/percona-toolkit. Include the following information in your bug report:
- Complete command-line used to run the tool
- Tool --version
- MySQL version of all servers involved
- Output from the tool including STDERR
- Input files (log/dump/config files, etc.)
If possible, include debugging output by running the tool with PTDEBUG; see “ENVIRONMENT”.
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:
Replace TOOL with the name of any tool.
ABOUT PERCONA TOOLKIT¶
This tool is part of Percona Toolkit, a collection of advanced command-line tools developed by Percona for MySQL support and consulting. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and developed primarily by him and Daniel Nichter, both of whom are employed by Percona. Visit http://www.percona.com/software/ for more software developed by Percona.
COPYRIGHT, LICENSE, AND WARRANTY¶
This program is copyright 2011-2013 Percona Ireland Ltd.
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.