introduction to linear optimization

Article Title: apache Optimization Configuration introduction. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source. 1. Compile and install apache In Apache source code, the default maximum number of processes is 256. You need to modify/src/include/httpd. h.# Ifndef HARD_SER

Mysql Performance Optimization script mysqltuner. pl usage introduction bitsCN.com MySQLTuner: http://github.com/rackerhacker/MySQLTuner-perl MySQLTuner usage:Downloading and using MySQLTuner is actually a very simple process: Wget mysqltuner. plPerl mysqltuner. pl If you 'd rather not invoke perl every time, just make it executable: Chmod u + x mysqltuner. pl./Mysqltuner. pl » Latest development versionIf

Date: Display timeDate-s "2015/05/21 14:46" modification timeHwclock rinse into the clock insideCal Display CalendarNtpdate time.nist.gov Sync Internet timeWrite synchronization time to Scheduled tasks:echo "*/5 * * * * */usr/sbin/ntpdate time.nist.gov >dev/null 2>1 ">>/var/spool/cron/rootThe wrong and correct outputs are put into the black hole >dev/null 2>1The following 3 methods are equivalent/dev/null Empty Device black hole1) 1>/dev/null 2>log/dev/null2) * * * * * 1>/dev/null 2>13) >/dev/nu

1. Definition:Modules: Logically organizing python code (variables, functions, classes, logic: Implementing a function, which is essentially the. py end of the file)2. How to ImportImport Module_name,module_name2,......From module import Module1,module2,....From module import logger as xxx: equals an alias for the imported moduleThe From module import * may have the same name as the existing module under the current path3.import Nature (Path search and search path)The essence of the import packa

tasks directly) Usage scenarios: 8. The Oracle Resource Manager is designed to make the database system manageable, without crashing through too many system resources. 9, the maximum number of connections to the Oracle database connection pool is not higher the better, generally set to the total number of CPU threads to achieve the best performance. Before setting: After setting: Cast Sword Team Signature: "Director" 12 Spring and Autumn,[email protected]; "Master" The rice is not pale,

last_name limit 20;(select First_name,last_name from actor order by last_name limit) union (select First_name,last_name from Customer Ord Er by last_name limit, order by last_name limit 20;Querying and updating on the same tableUpdate Foo as outer set cnt= (SELECT COUNT (*) from Foo as inner where inner.type=outer.type);Update foo JOIN (select Type,count (*) as CNT from Foo Group by type) as Der using (type) set foo.cnt=der.cnt;3) Optimize specific related queriesOptimize correlation:Explain se

check the Keep enumerations option, Because Ching this option causes the Java.lang.Enum to appear in the Configration file, this class is only available in a 1.5 environment. The error message is as follows:[Proguard] Note:the configuration refers to the unknown class ' Java.lang.Enum '[Proguard] Note:there were 1 references to unknown classes.[Proguard] You should check your the configuration for typos.5. When embedding an ant script, there is usually aTask.properties in Proguard.jar, reserved

index for our queries:MySQL could have used a range access to check the idExtra columnThis column shows the additional information that is not available in the other columns, and the MySQL document shows most of the values that can appear in this column, the most important ones you can see frequently are as follows:Using IndexMySQL uses an overlay index to avoid direct access to table data, and does not confuse the overlay index with the index access type.Using whereWhen MySQL retrieves data fr

statistics; use Oder by Rand () with caution. Third, the analysis of diagnostic tools in the daily development work, we can do some work to prevent slow SQL problems, such as pre-launch the use of diagnostic tools to analyze SQL. Commonly used tools are: Mysqldumpslowmysql profilemysql explain four, error operation, program bug how to do a mature enterprise often has perfect data management norms and a richer data recovery program (except for startups), Data backup and data disaster recovery. W

AWR Introduction to Performance optimization ToolsThis article mainly introduces oracle10g new awr tool, I often need to use AWR for database performance optimization and fault diagnosis in my work. AWR (Automatic workload Repository) is a new tool for collecting database statistics from Oracle 10g. It mainly includes awr memory area, historical data storage fil

catalog and then turn to the page numbers you need.3. Brief summary Indexes can improve query efficiency Clustered index A table can have only one, and a table with a nonclustered index may have multiple Clustered index storage records are physically contiguous, while nonclustered indexes are logically contiguous, and physical storage is not contiguous Also, it is well known that indexes can actually improve query speed, but it will affect the efficiency of insertions, del

Before the introduction, a simple say asp.net service side gzip compression module function and working principle, a lot of people write the page because of the use of a lot of JS special effects or put a lot of large dynamic ads caused the page or script bulky, Usually use some compression tools local to the page or script to a certain compression and then upload to the server, but such compression tool general compression rate is limited,

columns is the physical storage order of the table records, and once the column values change, the order of the entire table records will be adjusted, which can consume considerable resources. If your application needs to update clustered index data columns frequently, you need to consider whether the index should be built as a clustered index. Use a numeric field as much as possible , and if a field that contains only numeric information is not designed to be a character type, it can degrade q

tried to do this using the following SQL (for the sake of comparison, the columns of both tables are output): SELECT stu.name, stu.class, s.name, s.score FROM student AS stu LEFT JOIN score AS s ON stu.name = s.name AND stu.class = ‘A‘ At first glance, there seems to be no problem, but also left the connection and on the condition of the increase in class restrictions, in fact, the results appear in Class B classmate, why? It is because of the SQL execution o

|+----+-------------+---------+-------+---------------+---------+---------+-------+------+-------+1 row in Set#Simple means high efficiency,key is not empty to walk index Mysql> Explain select * from student where sdept= ' noon professional ';+----+-------------+---------+------+---------------+------+---------+------+------+-------------+| ID | Select_type | Table | Type | Possible_keys | Key | Key_len | Ref | Rows | Extra |+----+-------------+---------+------+---------------+------+---------+