sql performance tuning techniques

support Create compressed data page19, can dynamically turn off the InnoDB update metadata statistics function: Pollution buffer pool, annlyze table and Show table status will also read the table metadata pollution buffer pool20. Enhanced copy function21. Relay Log Self-repair22, open InnoDB Strict check mode23, dynamically change the system configuration parameters, new parameters can be changed dynamically is a separate table space, InnoDB lock timeout time24. Changes in

a text teaches you database performance tuning (attached to a large hospital real case) Preface An engineer at Microsoft once had a very figurative metaphor for performance tuning: Peeling onions. I also very much agree, let us to a layer of a layer of the outside its mysterious veil. six major factors The followi

feature that accelerates SQL adjustment as a whole.Through SPA, once a load (called SQL tuning set or STS) is created, Oracle will use the complex prediction module to repeatedly execute the workload (To obtain the best SQL Execution Plan for the current load. With SPA, we can predict the impact of an

operations, although PHP file operation efficiency is not low;41, optimize the Select SQL statement, as far as possible, as little as possible to insert, update operation (on the update, I was a bad batch);42, as far as possible the use of PHP internal functions (but I have to find a php non-existent function, wasted can write a custom function of time, experience problem ah!);PS: Built-in functions are nearly an order of magnitude more efficient tha

. server.2005. Technical Insider "series Conclusion This article first to this bar, short, easy to understand, this article mainly introduces the query plan of the joint operators, the next we analyze SQL Server parallel operations, in multicore hyper-threading gathered today, see SQL How server uses parallel operations to maximize the use of existing hardware resources to improve

filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster.The code is as follows:Low efficiency:SELECT JOB, AVG (SAL)From EMP GROUP job has job = ' president ' and AVG (SAL) >xxxEfficient:SELECT JOB, AVG (SAL)From EMPWHERE JOB = ' President 'OR job = ' MANAGER ' GROUP JOB having and AVG (SAL) >xxx7, usually, if the statement can avoid the use of subqueries, as far as possible without sub-query.Because the overhead

logEnabled by default Vim/etc/my.cnf[Mysqld]Options: Wq#systemctl Stop mysqld;#systemctl start mysqld; Error log: Log error messages generated by the service during startup and operationLog-error=/var/log/mysqld.log Query log: Records all SQL commands that are executed after the client connects to the service.[Mysqld]General-log cat/var/lib/mysql/host name. Log Slow query log: Displays the query result SQL

oracle| Data | database | Performance Oracle is a high-performance database software. The user can adjust the parameters to achieve the optimization of performance. Performance optimization is mainly divided into two parts: first, the database administrator through the adjustment of system parameters to achieve the goa

This article mainly tells you that there are 20 difficult problems in DB2 Performance Tuning. In actual DB2 database design, the physical design should be as close as possible to the logical structure, however, physical design changes made for DB2 performance cannot be ignored because they do not come from logical design. 1. Logical design should always be fully

does not exist in the table. (2) ' | | ' is a character join function. As with other functions, the index is deactivated. (3) ' + ' is a mathematical function. As with other mathematical functions, the index is deactivated. (4) The same index columns cannot be compared to each other, which will enable full table scanning.(+)A. If the number of records in a table that has more than 30% data is retrieved. Using indexes will have no significant efficiency gains.B. In certain situations, using an i

Usually SQL database needs optimization analysis, and there are some techniques, SQL optimization of several methods here do not do a detailed introduction, this article will be summarized in SQL statement optimization, followed by an optimization tool SQL

Mysql Tomcat C3p0 System Performance Tuning personal summary, System Information The application logic is to use c3p0 to query data in the database and return Json data over http. 1. the initial test result JMeter test result before optimization No. Type Original 1000 data bigger 1 500 Connection 250 query/S 63q/S70q/S 2 1000 connections 255q/S 57q/S65

you to optimize the SQL statement for join. Also, the fields that are used for join should be of the same type. For example, if you want to join a DECIMAL field with an INT field, MySQL cannot use its index. For those string types, you also need to have the same character set. (The character set of two tables may be different) "Avoid select *" "always set an ID for each table" We should set an ID for each table in the database as its primary key, a

|| Slow_launch_time | 2 |+------------------+-------+Mysql> show global status like '%slow% ';+---------------------+-------+| variable_name | Value |+---------------------+-------+| Slow_launch_threads | 0 || slow_queries | 4148 |+---------------------+-------+The configuration of the record slow query, the execution time of more than 2 seconds is slow query, the system shows that there are 4,148 slow query, you can analyze the slow query log, find the problem of

-------------------------------------------------------------------------| Id | Operation | Name | Cost (%CPU) |-------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 4 (0) || 1 | TABLE ACCESS by GLOBAL INDEX rowid| SALES | 4 (0) || 2 | INDEX RANGE SCAN | Index_qu_sold | 3 (0) |-------------------------------------------------------------------------9 Rows selectedSql> alter session Set "_use_nosegment_indexes" =true;Session altered.Sql> CREATE index

Guide: I had a feeling, no matter what tuning method, index is the most fundamental method, is the internal strength of all optimization techniques, so weSome of the tuning methods related to indexing are discussed. Indexes are a common method of improving database performance, which allows the database server to retri

Index | performance ORA FAQ Performance Tuning Series-- The Oracle (tm) Users ' co-operative FAQ Why would a reverse index to useful when the leading column of the "index is" generated from a sequence? When the first column of the index is generated by the sequence, what is the use of a reverse index? --------------------------------------------------------------

and reduced sorting. In the real world, optimized indexes are primarily considered in the following ways: The higher the filter, the more forward the field needs to be. Core SQL Overlay index to ensure maximum efficiency; The sorting field enters the index without interfering with the filter; Multi-SQL comprehensive consideration, re-use index; The third is to find the appropriate proportions by controllin

Hive General learners and trainers in the performance optimization of the general will be from the syntax and parameters of these tricks point of view, but not revolutionary optimization of hive performance, the reasons for this phenomenon are: 1, historical reasons and stereotypes: When you learn SQL is generally a stand-alone db, this time your

threads.Of course, here are a few thread operations can set their own, the maximum recommended for the current system configuration of the logical core number, of course, the large set can be just useless.Second , index Hint hints (index Hint)The so-called index hint hint is to force the query optimizer to perform a scan of a query statement or use a specified index.In this way, we often use in the tuning of a way, many times we create the index is i