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baron@percona.com
2012-05-24 16:55:51 -04:00
parent 55d0dedce2
commit c9050f0d61
1 changed files with 14 additions and 26 deletions
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@@ -6549,21 +6549,14 @@ pt-query-advisor - Analyze queries and advise on possible problems.
Usage: pt-query-advisor [OPTION...] [FILE] Usage: pt-query-advisor [OPTION...] [FILE]
pt-query-advisor analyzes queries and advises on possible problems. pt-query-advisor analyzes queries and advises on possible problems. It can read
Queries are given either by specifying slowlog files, --query, or --review. queries from several types of log files, or you can use the --query or --review
options.
Analyze all queries in a slow log: To analyze all queries in a MySQL slow query log file:
pt-query-advisor /path/to/slow-query.log pt-query-advisor /path/to/slow-query.log
Analyze all queries in a general log:
pt-query-advisor --type genlog mysql.log
Get queries from tcpdump using pt-query-digest:
pt-query-digest --type tcpdump.txt --print --no-report | pt-query-advisor
=head1 RISKS =head1 RISKS
The following section is included to inform users about the potential risks, The following section is included to inform users about the potential risks,
@@ -6572,10 +6565,8 @@ are those created by the nature of the tool (e.g. read-only tools vs. read-write
tools) and those created by bugs. tools) and those created by bugs.
pt-query-advisor simply reads queries and examines them, and is thus pt-query-advisor simply reads queries and examines them, and is thus
very low risk. very low risk. At the time of this release we know of no issues that could harm
users.
At the time of this release there is a bug that may cause an infinite (or
very long) loop when parsing very large queries.
The authoritative source for updated information is always the online issue The authoritative source for updated information is always the online issue
tracking system. Issues that affect this tool will be marked as such. You can tracking system. Issues that affect this tool will be marked as such. You can
@@ -6586,11 +6577,8 @@ See also L<"BUGS"> for more information on filing bugs and getting help.
=head1 DESCRIPTION =head1 DESCRIPTION
pt-query-advisor examines queries and applies rules to them, trying to pt-query-advisor applies rules to queries, looking for potential problems.
find queries that look bad according to the rules. It reports on It prints a report of queries that match rules.
queries that match the rules, so you can find bad practices or hidden
problems in your SQL. By default, it accepts a MySQL slow query log
as input.
=head1 RULES =head1 RULES
@@ -6701,9 +6689,9 @@ GROUP BY or ORDER BY different tables will force a temp table and filesort.
severity: warn severity: warn
ORDER BY different directions prevents index from being used. All tables ORDER BY clauses that sort the results in different directions prevents indexes
in the ORDER BY clause must be either ASC or DESC, else MySQL cannot use from being used. All expressions in the ORDER BY clause must be ordered either
an index. ASC or DESC so that MySQL can use an index.
=item COL.001 =item COL.001
@@ -6806,9 +6794,9 @@ severity: crit
IN() and NOT IN() subqueries are poorly optimized. MySQL executes the subquery IN() and NOT IN() subqueries are poorly optimized. MySQL executes the subquery
as a dependent subquery for each row in the outer query. This is a frequent as a dependent subquery for each row in the outer query. This is a frequent
cause of serious performance problems. This might change version 6.0 of MySQL, cause of serious performance problems. This might improve in version 5.6 of
but for versions 5.1 and older, the query should be rewritten as a JOIN or a MySQL, but for versions 5.1 and older, the query should be rewritten as a JOIN
LEFT OUTER JOIN, respectively. or a LEFT OUTER JOIN, respectively.
=back =back