postgresql query optimization tips

the nature of the method, and calling this method does not change the state of the object.28. The use of intrinsic get,set methods should be avoided wherever possible.In Android programming, the invocation of a virtual method has a lot of cost, more than the cost of an instance property query. We should use the Get,set method when we outsource the call, but it should be called directly when it is called internally.29. Avoid enumeration, use of floati

function-oriented table. This colleague is also a good practice because she tells you how to distinguish the nature of the method, and calling this method does not change the state of the object.28. The use of intrinsic get,set methods should be avoided wherever possible.In Android programming, the invocation of a virtual method has a lot of cost, more than the cost of an instance property query. We should use the Get,set method when we outsource the

problem.27. Consider using static methods,If you don't have to go to the outside of the object, make your method a static method. She will be called faster because she does not need a virtual function-oriented table. This colleague is also a good practice because she tells you how to distinguish the nature of the method, and calling this method does not change the state of the object.28. The use of intrinsic get,set methods should be avoided wherever possible.In Android programming, the invocat

You have completed your brand's new application, and everything works like a charm. To use your network. Everyone is happy.Then, suddenly, an explosive user killed your MySQL server and your website was closed. What's wrong? How can you stop it?The following are some tips for MySQL performance optimization, which will help you and your database.Focus on In the early stages of development, you should know th

through the component.createvolatileimage () or Graphicsconfiguration.createcompatiblevolatileimage () method.　　3.9 using Window blittingWhen scrolling, all visible content is generally redrawn, resulting in a lot of unnecessary redrawing work. Many operating system graphics subsystems, including WIN32 GDI, MacOS, and x/windows, Support window blitting technology. Window blitting Technology moves the graphic to a new location directly in the screen buffer, redrawing only the newly emerging area

where the row resides, the data block and the position of the row in the block, so access to the data via rowID can be quickly located on the target data. is the fastest way for Oracle to access single-row data.3. Index Scan: The ROWID value of an object is first found by index, and then the specific data is found directly from the table through the ROWID value, which can greatly improve the efficiency of the search.2. Table Order of connection queriesBy default, the optimizer uses the All_rows

TABLE #t (...)13, a lot of times with exists instead of in is a good choice:Select num from a where num in (select num from B)Replace with the following statement:Select num from a where exists (select 1 from b where num=a.num)14, not all indexes are valid for the query, SQL is based on the data in the table to query optimization, when the index column has a lar

Label:For database optimization: The goal of database optimization is to avoid disk I/O bottlenecks, reduce CPU utilization, and reduce resource contentionThe design of database table based on the third paradigm has many advantages:One is to eliminate redundant data, saving disk storage space;Second, there is a good data integrity limit, that is, based on the primary foreign key reference complete limit and

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!);44, the loop inside do not declare variables, especially large variables: objects (this does not seem to be the only thing in PHP to pay attention to it?);45, multidimensional arrays try not to loop nested assignment;46, in the case of PHP internal string manipulation function, do not use regular expressions;47, foreach more efficient, t

columns is the physical storage order of the table records, and once the column values change, the order of the entire table records is adjusted,Will cost a considerable amount of 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.15. Use numeric fields as much as possible, if the field containing only numeric information should not be designed as a character type, which will reduce

consumption of sorting results, you can use ORDER by NULL to suppress sorting. For example: SELECT * FROM Dept GROUP by ename ORDER by NULL;4, in some cases, you can use a connection instead of a subqueryBecause you use Join,mysql, you do not need to create temporary tables in memory.5, if you want to use an index in a query statement that has or, you must use an index for each condition between or, and if you do not have an index, you should conside