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  #1 (permalink)  
Old 02-28-2008, 07:02 AM
Alexander Bespalov
 
Posts: n/a
Default SELECT Speed
Hi,

I have a problem with SELECT speed. The first execution takes up to several
minutes while the next (with the same statement) takes not more then several
seconds.

The statement example is:
select nas.nasIpAddress, count(distinct(acct.user_id)), count(*),
sum(acct.acctOutputOctets) from acct, nas, can, acctStatusType where
acct.can_id = can.id and acct.acctStatusType_id = acctStatusType.id and
acct.day >= '2007-09-01'
and acct.day <= '2007-11-01'
and acct.nas_id = nas.id
and can.can = 10
and acctStatusType.acctStatusType = 'Stop'
group by acct.nas_id
;

EXPLAIN shows the following:
+----+-------------+----------------+--------+------------------------+-----
-----------+---------+-----------------+-------+----------------+
| id | select_type | table | type | possible_keys | key
| key_len | ref | rows | Extra |
+----+-------------+----------------+--------+------------------------+-----
-----------+---------+-----------------+-------+----------------+
| 1 | SIMPLE | can | const | PRIMARY,can | can
| 2 | const | 1 | Using filesort |
| 1 | SIMPLE | acctStatusType | const | PRIMARY,acctStatusType |
acctStatusType | 10 | const | 1 | |
| 1 | SIMPLE | acct | ref | index1 |
index1 | 4 | const,const | 63827 | Using where |
| 1 | SIMPLE | nas | eq_ref | PRIMARY |
PRIMARY | 4 | GWF.acct.nas_id | 1 | |
+----+-------------+----------------+--------+------------------------+-----
-----------+---------+-----------------+-------+----------------+

I have the following table with 59742411 rows:
mysql> describe acct;
+-----------------------+-----------------------+------+-----+--------------
-------+-------+
| Field | Type | Null | Key | Default
| Extra |
+-----------------------+-----------------------+------+-----+--------------
-------+-------+
| date | datetime | | | 0000-00-00
00:00:00 | |
| user_id | int(10) unsigned | | PRI | 0
| |
| nas_id | int(10) unsigned | | PRI | 0
| |
| can | smallint(5) unsigned | YES | | NULL
| |
| can_id | smallint(5) unsigned | YES | MUL | NULL
| |
| acctStatusType_id | tinyint(3) unsigned | | PRI | 0
| |
| acctTerminateCause_id | tinyint(3) unsigned | | | 0
| |
| sweetEventContext_id | tinyint(3) unsigned | | | 0
| |
| acctSessionId | varchar(8) | | PRI |
| |
| acctDelayTime | mediumint(8) unsigned | | | 0
| |
| acctSessionTime | mediumint(8) unsigned | YES | | NULL
| |
| acctInputOctets | bigint(20) unsigned | YES | | NULL
| |
| acctOutputOctets | bigint(20) unsigned | YES | | NULL
| |
| wisprBwMaxUp | int(10) unsigned | YES | | NULL
| |
| wisprBwMaxDown | int(10) unsigned | YES | | NULL
| |
| day | date | | PRI | 0000-00-00
| |
| acctMultiSessionId | varchar(27) | YES | | NULL
| |
+-----------------------+-----------------------+------+-----+--------------
-------+-------+
mysql> show index from acct;
+-------+------------+----------+--------------+-------------------+--------
---+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name |
Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------+------------+----------+--------------+-------------------+--------
---+-------------+----------+--------+------+------------+---------+
| acct | 0 | PRIMARY | 1 | user_id | A
| 53341 | NULL | NULL | | BTREE | |
| acct | 0 | PRIMARY | 2 | nas_id | A
| 277871 | NULL | NULL | | BTREE | |
| acct | 0 | PRIMARY | 3 | acctStatusType_id | A
| 558340 | NULL | NULL | | BTREE | |
| acct | 0 | PRIMARY | 4 | acctSessionId | A
| 59742411 | NULL | NULL | | BTREE | |
| acct | 0 | PRIMARY | 5 | day | A
| 59742411 | NULL | NULL | | BTREE | |
| acct | 1 | index1 | 1 | can_id | A
| 467 | NULL | NULL | YES | BTREE | |
| acct | 1 | index1 | 2 | acctStatusType_id | A
| 936 | NULL | NULL | | BTREE | |
| acct | 1 | index1 | 3 | day | A
| 88638 | NULL | NULL | | BTREE | |
| acct | 1 | index1 | 4 | nas_id | A
| 1659511 | NULL | NULL | | BTREE | |
+-------+------------+----------+--------------+-------------------+--------
---+-------------+----------+--------+------+------------+---------+

MySQL version is 4.1.20
What is the bottleneck in my server? How could I improve MySQL server
performance?

Thank you!

--
Alexander Bespalov

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  #2 (permalink)  
Old 02-28-2008, 07:02 AM
Martin Gainty
 
Posts: n/a
Default Re: SELECT Speed
You seem to have an over-reliance on BTREE Indexes over BITMAPPED Indexes or
HASH Indexes

There are specific rules governing implementation of BTREE Index
http://download-east.oracle.com/docs...14220/schema.h
tm#sthref893

As well as specific rules governing use of HASH Index
http://www.geekinterview.com/question_details/28844

not to forget rules governing use of BITMAP indexes
http://www.dba-oracle.com/oracle_tip...ed_indexes.htm

M-
----- Original Message -----
From: "Alexander Bespalov" <bespalov@sovintel.ru>
To: <mysql@lists.mysql.com>
Sent: Monday, November 26, 2007 10:03 AM
Subject: SELECT Speed


> Hi,
>
> I have a problem with SELECT speed. The first execution takes up to
several
> minutes while the next (with the same statement) takes not more then
several
> seconds.
>
> The statement example is:
> select nas.nasIpAddress, count(distinct(acct.user_id)), count(*),
> sum(acct.acctOutputOctets) from acct, nas, can, acctStatusType where
> acct.can_id = can.id and acct.acctStatusType_id = acctStatusType.id and
> acct.day >= '2007-09-01'
> and acct.day <= '2007-11-01'
> and acct.nas_id = nas.id
> and can.can = 10
> and acctStatusType.acctStatusType = 'Stop'
> group by acct.nas_id
> ;
>
> EXPLAIN shows the following:
>
+----+-------------+----------------+--------+------------------------+-----
> -----------+---------+-----------------+-------+----------------+
> | id | select_type | table | type | possible_keys |
key
> | key_len | ref | rows | Extra |
>
+----+-------------+----------------+--------+------------------------+-----
> -----------+---------+-----------------+-------+----------------+
> | 1 | SIMPLE | can | const | PRIMARY,can |
can
> | 2 | const | 1 | Using filesort |
> | 1 | SIMPLE | acctStatusType | const | PRIMARY,acctStatusType |
> acctStatusType | 10 | const | 1 | |
> | 1 | SIMPLE | acct | ref | index1 |
> index1 | 4 | const,const | 63827 | Using where |
> | 1 | SIMPLE | nas | eq_ref | PRIMARY |
> PRIMARY | 4 | GWF.acct.nas_id | 1 | |
>
+----+-------------+----------------+--------+------------------------+-----
> -----------+---------+-----------------+-------+----------------+
>
> I have the following table with 59742411 rows:
> mysql> describe acct;
>
+-----------------------+-----------------------+------+-----+--------------
> -------+-------+
> | Field | Type | Null | Key | Default
> | Extra |
>
+-----------------------+-----------------------+------+-----+--------------
> -------+-------+
> | date | datetime | | | 0000-00-00
> 00:00:00 | |
> | user_id | int(10) unsigned | | PRI | 0
> | |
> | nas_id | int(10) unsigned | | PRI | 0
> | |
> | can | smallint(5) unsigned | YES | | NULL
> | |
> | can_id | smallint(5) unsigned | YES | MUL | NULL
> | |
> | acctStatusType_id | tinyint(3) unsigned | | PRI | 0
> | |
> | acctTerminateCause_id | tinyint(3) unsigned | | | 0
> | |
> | sweetEventContext_id | tinyint(3) unsigned | | | 0
> | |
> | acctSessionId | varchar(8) | | PRI |
> | |
> | acctDelayTime | mediumint(8) unsigned | | | 0
> | |
> | acctSessionTime | mediumint(8) unsigned | YES | | NULL
> | |
> | acctInputOctets | bigint(20) unsigned | YES | | NULL
> | |
> | acctOutputOctets | bigint(20) unsigned | YES | | NULL
> | |
> | wisprBwMaxUp | int(10) unsigned | YES | | NULL
> | |
> | wisprBwMaxDown | int(10) unsigned | YES | | NULL
> | |
> | day | date | | PRI | 0000-00-00
> | |
> | acctMultiSessionId | varchar(27) | YES | | NULL
> | |
>
+-----------------------+-----------------------+------+-----+--------------
> -------+-------+
> mysql> show index from acct;
>
+-------+------------+----------+--------------+-------------------+--------
> ---+-------------+----------+--------+------+------------+---------+
> | Table | Non_unique | Key_name | Seq_in_index | Column_name |
> Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment
|
>
+-------+------------+----------+--------------+-------------------+--------
> ---+-------------+----------+--------+------+------------+---------+
> | acct | 0 | PRIMARY | 1 | user_id | A
> | 53341 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 2 | nas_id | A
> | 277871 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 3 | acctStatusType_id | A
> | 558340 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 4 | acctSessionId | A
> | 59742411 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 5 | day | A
> | 59742411 | NULL | NULL | | BTREE | |
> | acct | 1 | index1 | 1 | can_id | A
> | 467 | NULL | NULL | YES | BTREE | |
> | acct | 1 | index1 | 2 | acctStatusType_id | A
> | 936 | NULL | NULL | | BTREE | |
> | acct | 1 | index1 | 3 | day | A
> | 88638 | NULL | NULL | | BTREE | |
> | acct | 1 | index1 | 4 | nas_id | A
> | 1659511 | NULL | NULL | | BTREE | |
>
+-------+------------+----------+--------------+-------------------+--------
> ---+-------------+----------+--------+------+------------+---------+
>
> MySQL version is 4.1.20
> What is the bottleneck in my server? How could I improve MySQL server
> performance?
>
> Thank you!
>
> --
> Alexander Bespalov
>
>
> --
> MySQL General Mailing List
> For list archives: http://lists.mysql.com/mysql
> To unsubscribe: http://lists.mysql.com/mysql?unsub=mgainty@hotmail.com
>
>

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  #3 (permalink)  
Old 02-28-2008, 07:02 AM
Alex Arul Lurthu
 
Posts: n/a
Default Re: SELECT Speed
The second query might be faster due to caching.

On 11/26/07, Alexander Bespalov <bespalov@sovintel.ru> wrote:
> Hi,
>
> I have a problem with SELECT speed. The first execution takes up to several
> minutes while the next (with the same statement) takes not more then several
> seconds.
>
> The statement example is:
> select nas.nasIpAddress, count(distinct(acct.user_id)), count(*),
> sum(acct.acctOutputOctets) from acct, nas, can, acctStatusType where
> acct.can_id = can.id and acct.acctStatusType_id = acctStatusType.id and
> acct.day >= '2007-09-01'
> and acct.day <= '2007-11-01'
> and acct.nas_id = nas.id
> and can.can = 10
> and acctStatusType.acctStatusType = 'Stop'
> group by acct.nas_id
> ;
>
> EXPLAIN shows the following:
> +----+-------------+----------------+--------+------------------------+-----
> -----------+---------+-----------------+-------+----------------+
> | id | select_type | table | type | possible_keys | key
> | key_len | ref | rows | Extra |
> +----+-------------+----------------+--------+------------------------+-----
> -----------+---------+-----------------+-------+----------------+
> | 1 | SIMPLE | can | const | PRIMARY,can | can
> | 2 | const | 1 | Using filesort |
> | 1 | SIMPLE | acctStatusType | const | PRIMARY,acctStatusType |
> acctStatusType | 10 | const | 1 | |
> | 1 | SIMPLE | acct | ref | index1 |
> index1 | 4 | const,const | 63827 | Using where |
> | 1 | SIMPLE | nas | eq_ref | PRIMARY |
> PRIMARY | 4 | GWF.acct.nas_id | 1 | |
> +----+-------------+----------------+--------+------------------------+-----
> -----------+---------+-----------------+-------+----------------+
>
> I have the following table with 59742411 rows:
> mysql> describe acct;
> +-----------------------+-----------------------+------+-----+--------------
> -------+-------+
> | Field | Type | Null | Key | Default
> | Extra |
> +-----------------------+-----------------------+------+-----+--------------
> -------+-------+
> | date | datetime | | | 0000-00-00
> 00:00:00 | |
> | user_id | int(10) unsigned | | PRI | 0
> | |
> | nas_id | int(10) unsigned | | PRI | 0
> | |
> | can | smallint(5) unsigned | YES | | NULL
> | |
> | can_id | smallint(5) unsigned | YES | MUL | NULL
> | |
> | acctStatusType_id | tinyint(3) unsigned | | PRI | 0
> | |
> | acctTerminateCause_id | tinyint(3) unsigned | | | 0
> | |
> | sweetEventContext_id | tinyint(3) unsigned | | | 0
> | |
> | acctSessionId | varchar(8) | | PRI |
> | |
> | acctDelayTime | mediumint(8) unsigned | | | 0
> | |
> | acctSessionTime | mediumint(8) unsigned | YES | | NULL
> | |
> | acctInputOctets | bigint(20) unsigned | YES | | NULL
> | |
> | acctOutputOctets | bigint(20) unsigned | YES | | NULL
> | |
> | wisprBwMaxUp | int(10) unsigned | YES | | NULL
> | |
> | wisprBwMaxDown | int(10) unsigned | YES | | NULL
> | |
> | day | date | | PRI | 0000-00-00
> | |
> | acctMultiSessionId | varchar(27) | YES | | NULL
> | |
> +-----------------------+-----------------------+------+-----+--------------
> -------+-------+
> mysql> show index from acct;
> +-------+------------+----------+--------------+-------------------+--------
> ---+-------------+----------+--------+------+------------+---------+
> | Table | Non_unique | Key_name | Seq_in_index | Column_name |
> Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
> +-------+------------+----------+--------------+-------------------+--------
> ---+-------------+----------+--------+------+------------+---------+
> | acct | 0 | PRIMARY | 1 | user_id | A
> | 53341 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 2 | nas_id | A
> | 277871 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 3 | acctStatusType_id | A
> | 558340 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 4 | acctSessionId | A
> | 59742411 | NULL | NULL | | BTREE | |
> | acct | 0 | PRIMARY | 5 | day | A
> | 59742411 | NULL | NULL | | BTREE | |
> | acct | 1 | index1 | 1 | can_id | A
> | 467 | NULL | NULL | YES | BTREE | |
> | acct | 1 | index1 | 2 | acctStatusType_id | A
> | 936 | NULL | NULL | | BTREE | |
> | acct | 1 | index1 | 3 | day | A
> | 88638 | NULL | NULL | | BTREE | |
> | acct | 1 | index1 | 4 | nas_id | A
> | 1659511 | NULL | NULL | | BTREE | |
> +-------+------------+----------+--------------+-------------------+--------
> ---+-------------+----------+--------+------+------------+---------+
>
> MySQL version is 4.1.20
> What is the bottleneck in my server? How could I improve MySQL server
> performance?
>
> Thank you!
>
> --
> Alexander Bespalov
>
>
> --
> MySQL General Mailing List
> For list archives: http://lists.mysql.com/mysql
> To unsubscribe: http://lists.mysql.com/mysql?unsub=a...rthu@gmail.com
>
>

--
Sent from Gmail for mobile | mobile.google.com

Thanks
Alex
http://alexlurthu.wordpress.com
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  #4 (permalink)  
Old 02-28-2008, 07:02 AM
mos
 
Posts: n/a
Default Re: SELECT Speed
At 05:57 PM 11/26/2007, you wrote:
>The second query might be faster due to caching.

This can be verified by executing:

RESET QUERY CACHE

before executing the second query. This will clear the queries from the cache.

Mike
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  #5 (permalink)  
Old 02-28-2008, 07:02 AM
Perrin Harkins
 
Posts: n/a
Default Re: SELECT Speed
On Nov 27, 2007 10:21 AM, mos <mos99@fastmail.fm> wrote:
> At 05:57 PM 11/26/2007, you wrote:
> >The second query might be faster due to caching.
>
> This can be verified by executing:
>
> RESET QUERY CACHE
>
> before executing the second query. This will clear the queries from the cache.

No need to blow your whole cache. Just do this on the session you test from:

SET SESSION query_cache_type = OFF;

However, while this disables the query cache, it doesn't reset the
caching of disk data, which is the most likely reason for queries to
run faster the second time. The needed index or data records will be
in RAM the second time the query is run.

- Perrin
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