elasticsearch query performance tuning

Summary of Oracle Performance Tuning recommendationsPrinciple One: Note the connection order in the WHERE clause:Oracle uses a bottom-up sequential parsing where clause, according to which the connection between tables must be written before other where conditions, and those that can filter out the maximum number of records must be written at the end of the WHERE clause.Especially "PRIMARY key id=?" "Such a

This article describes some of the most useful ways to adjust the JSP and servlet to make your servlet and JSP pages respond faster and more scalable. And in the case of increasing the number of users, the system load will show a trend of smooth and long. In this article, I'll use some examples and configuration methods to make your application's performance unexpectedly elevated. Some of these tuning techn

Label:16th: Improving performance with indexes 1. CREATE index Single field index: CREATE INDEX INDEX_NAME on table_name (COLUMN_NAME);Unique index: Create unique index index_name on table_name (COLUMN_NAME); Combined index: An index of two or more fields in a table CREATE INDEX index_name on table_name (COLUMN1,COLUMN2); 2. When to consider setting the index 3, DROP index index_name; Delete Index 4, ALTER index index_name; modifying indexes 20th ch

1. Import the trace file into the tableSELECT IDENTITY (BIGINT11 as RowNumber,* into TableNamefrom fn_trace_gettable ('trace.trc'default)2. Querying for statements with large CPU overheadSELECT Top -Total_worker_time/Execution_count asAvg_cpu_cost, Plan_handle, Execution_count, (SELECT SUBSTRING(text, Statement_start_offset/2 + 1, ( Case whenStatement_end_offset= -1 Then LEN(CONVERT(nvarchar(Max),text))* 2 ELSEStatement_end_offsetEND -Statement_start_offset)/2) fro

be sorted, or it can be added to a column (like joins or additions). Any non-indexed item in the ORDER BY statement, or a computed expression, will slow down the query. Double-check the order BY statement to find non-indexed items or expressions that degrade performance. The solution to this problem is to rewrite the order BY statement to use the index, or you can establish another index for the column you

may be a little bit small, or too much fragmentation. Query Cache Hit Ratio = (qcache_hits-qcache_inserts)/qcache_hits * 100% Sample server query Cache Fragmentation rate = 20.46%, query cache utilization = 62.26%, query cache Hit Ratio = 1.94%, hit ratio is poor, probably write more frequently, and possibly some frag

the data from disk into the Oracle buffer cache. if this happens too often the performance of the query or the entire database can suffer. typically this is caused by contention for "hot" blocks or objects so it is imperative to find out which data is being contended. once that is known this document lists several alternative methods for solving the issue. conclusion: Two or more sessions simultaneously ne

on static file compression />2. Optimizing the JVM for catalina.shOpen the Tomcat path \bin\ catalina.sh, add at the top, red part please adjust according to the actual situationJava_opts= "-server-showversion-xms12g-xmx12g-xx:permsize=256m-xx:maxpermsize=256m "java_opts= "$JAVA _opts-d64-xx:cicompilercount=8-xx:+usecompressedoops"java_opts= "$JAVA _opts-xx:survivorratio=4-xx:targetsurvivorratio=90"java_opts= "$JAVA _opts-xx:reservedcodecachesize=256m-xx:-useadaptivesizepolicy"java_opts= "$JAVA

at this timeOpen log file discovery occurrence recordLater, you can only check the log file periodically to find the slow query statement.Attention:After finding the slow query statement, to confirm the slow query by repeatedly using the SELECT statement, note that only SELECT statements can be used, even if the original statement is delete or update, etc., also

Label:Original address: Http://social.technet.microsoft.com/wiki/contents/articles/4995.sql-server-columnstore-performance-tuning.aspxSQL Server's Columnstore index is a new version of SQL Server release that improves query performance for the Data Warehouse, and this article explains the performance

union and UnionAll. UnionAll Good 18, pay attention to using distinct, do not use when not necessary, it will make the query slower than the union. Duplicate records are not a problem in the query. 19. Do not return rows or columns that are not required when querying 20. Use sp_configure ' query governor cost limit ' or setquery_governor_cost_limit to limit the

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 performance opti

Label:MySQL is a powerful open source relational database management system (RDBMS). It was posted on 1995 (20 ago). It uses Structured Query Language (SQL), which may be the most popular choice in database content management. The latest MySQL version is 5.6.25, released on May 29, 2015. An interesting fact about MySQL is that its name comes from the daughter "My" of Michael Widenius (the founder of MySQL). Although there are many interesting rumors a

, the not-in clause performs an internal sort and merge. In either case, not in is the least effective (because it performs a full table traversal of the table in the subquery). To avoid using not, we can change it to an outer join (Outer Joins) or not EXISTS. 20. Replacing exists with a table connection typically, table joins are more efficient than exists 21. Replace distinct with exists when you submit a query that contains one-to-many table inform

an execution plan, and stored in a database of SQL statements, is a collection of control flow language, the speed of course fast. 48, the return value of the function is not too large, this overhead is very large. A user-defined function that executes as a cursor consumes a large amount of resources if a large result is returned with a stored procedure. 49, as far as possible to avoid repeated access to the same or several tables, especially the large number of data tables, you can consider th

keys from table_nameTime to create an index:Generally need to be indexed in the where and join clausesConsiderations for Using Indexes:In some cases like needs to be indexed, because in a wildcard % and - start query,mysql Do not use indexesSELECT * from table-name where name like ' % admin'; Besides, there's no way to do the math on the list.SELECT * from Users where Year (adddate) The operation on each row will cause the index to fail and perform

established, the System.IDisposable interface should be inherited, and the resources will be forced to be freed, so that the problem of insufficient number of connections can not occur.Solution TwoWorkaround (*): Web.config: In the database connection add Max Pool Size = 512;server=local;uid=;p wd=;d atabase=2004; Max Pool Size = 512; " > Once and for all.Solution ThreeIt is estimated that the connection (Connection) object does not have close. It is not necessary to dispose, and DataReader sho

index, the TPS from the previous 110 to 6000 such. Two. The SQL statement index does not work: When performing a performance test, the server is running under the circumstances: The CPU of the database is up to 90%-99.9%, and the CPU of the application is low; Sufficient memory (free memory >20m); Network normal; Disk input/output is normal; CPU-High Monitor diagram The logs are not printing errors, but the TPS is very l

the query, and Usingfilesort will appear. Sorting naturally increases query time, resulting in slower efficiency. The workaround is to use the index for sorting. If the order required for the query is the same as the sort used by the index, because the indexes are sorted, and therefore the results are returned in sequential read by index, the using Filesort does

GROUP BY:Increase the efficiency of the group BY statement by filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster.Copy CodeThe 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 o