I am using MySQL Workbench on Windows. How do I find out the time taken to execute a query like
Select * from employers where employerid > 200
Is there a statement I can enter that returns the execution time for this query?
Thanks
MySQL workbench is the way to go for things like this (optimization, benchmarking of queries, etc.). You say you're not familiar with it, so I'd recommend reading a tutorial from the good folks at MySQL
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We only have two Junior DBAs, no Senior DBAs, no one to guide us. We need to review each and every query for almost 30 large projects. Each query took between 5 minutes and two hours depending on the query. As a reviewer, it was a real drag on my time.
My question is, do MySQL can do automatic EXPLAIN on each query, without having to run EXPLAIN by hand and log the result of un-optimized queries? Or maybe by cronjob? If possible, how to do this?
If using mariadb there is log-slow-verbosity=query_plan,explain.
Alternately pt-query-digest has an --explain option to point to the server to run the explain query.
In oracle sql plus, while doing performance testing, I would do
set autotrace traceonly:
which would display the query plan and statistics without printing the actual results. Is there anything equivalent in mysql?
No, there's no equivalent available in MySQL, at least not in the community edition.
MySQL does not implement the kind of "instrumentation" that Oracle has in its code; so there's no equivalent to an event 10046 trace.
You can preface your SELECT statement with the EXPLAIN keyword, and that will produce output with information about the execution plan that MySQL would use to run the statement, but that's just an estimate, and not a monitoring of the actual execution.
You can also enable the slow query log on the server, to capture SQL statements that take longer than long_query_time seconds to execute, but that really only identifies the long running queries. That would give you the SQL text, along with elapsed time and a count of rows examined.
To get the query plan, just add EXPLAIN to the beginning of a SELECT query.
EXPLAIN SELECT * FROM table
It also estimates the number of rows to be read if that's what statistics you're talking about.
Can anyone suggest a good MYSQL optimization tool which helps in finding the bottlenecks in a long query and hence help in optimization?? I am looking for a query profiler.
thanks...
Well, You mean Query Optimization? I guess EXPLAIN <query> is excellent in giving hits as to where the bottlenecks are. After which redefine you indexes & ...
UPDATE1: You could check out - MySQL optimization tools
UPDATE2: After digging up in my code, I see that I used to do 2 things for query optimization.
Turn on Slow Query Log - MySQL can record expensive SQL queries in the slow query log. You can define your expectations in seconds using parameter long_query_time.
mysqldumpslow command - After logging is turned on you can analyze the log contents using mysqldumpslow command. mysqldumpslow /path/to/your/mysql-slow-queries.log -t 10. This will show you top 10 performance killers. For each statement in the output you can see the number of identical calls, execution time in seconds, rows affected and the statement itself.
I'm an mssql veteran who's received a job that involves tuning a mysql db. with mssql it was simply a matter of firing up the db profiler and then crunching up the data it collects. I can't seem to find anything similar for mysql.
thanks in advance
You can enable the PROFILER in the mysql query tool and profile individual statements. Also see Using the New MySQL Query Profiler or How to profile a query in MySQL.
You can also use EXPLAIN to get the query optimization plan, but it only works for SELECT queries.
I found EXPLAIN SELECT query very useful in MySQL because it gives information on how SQL will be executed and gives the opportunity to analyze, for e.g., missing indexes you should add in order to improve response BEFORE doing the query itself and analyzing stats.
My question is: In databases like MS Sql, Firebird, Ingres, is there a similar command available?
In Firebird we have PLAN, but is very weak because many times one has to run very long queries in order to view a simple mistake.
Best regards,
Mauro H. Leggieri
In Oracle:
EXPLAIN PLAN FOR SELECT …
In PostgreSQL:
EXPLAIN SELECT …
In SQL Server:
SET SHOWPLAN_XML ON
GO
SELECT …
GO
For mssql server you can use
SET SHOWPLAN_TEXT ON and SET SHOWPLAN_TEXT OFF
this will prevent queries from actually being exectued but it will return they query plan.
For oracle you can use
SET AUTOTRACE ON or EXPLAIN PLAN
(I don't know about firebird or ingres)
In Oracle we have
EXPLAIN PLAN for sql
http://www.adp-gmbh.ch/ora/explainplan.html
In MS SQL Server you can get an text or XML version of the execution plan.
SET SHOWPLAN_XML ON|OFF
SET SHOWPLAN_TEXT ON|OFF
However these are best viewed using the visual tool in Sql Server Management Studio/TOAD.
http://msdn.microsoft.com/en-us/library/ms176058.aspx
Something else that is quite handy is
SET STATISTICS IO ON|OFF
For Ingres, the following will give you the final plan chosen with estimates as to the number of rows, disk IOs and CPU cycles:
set qep
To get the plan but not execute the SELECT also add
set optimizeonly
re-enable query execution:
set nooptimizeonly
to get the the actual statistics for the executed query, to compare with the output from "set qep":
set trace point qe90
See http://docs.ingres.com/Ingres/9.2/SQL%20Reference%20Guide/set.htm for more information on the above.
MS SQL has a utility in Management Studio called Display Execution Plan (Estimated and Exact) when executing a query. it can also display statistics for the query (run time, number of rows, traffic etc )
For Ingres, see also these resources:
Example of Reading and Interpreting a Query Execution Plan (QEP) [pdf]
A brief case study that demonstrates analysis and interpretation of a QEP
Getting Ingres Qep LockTrace Using JDBC
The Query Execution Plan (QEP)