In the context of a database, optimisation refers to the process of the query optimiser selecting an efficient physical execution plan.

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Optimising MySQL

As per this post, it looks like I'm having some serious issues with MySQL optimisation. Unfortunately, I have no idea where to start! I'm running a DirectAdmin-based CentOS dedicated server. It's an ...
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What are the key points to avoid table locks?

MySQL is using at my company and most of the database administration works on trying to solve the table locks. What are the key points to avoid table locks(I mean at database side and even at software ...
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if database is not shrinked does it affect backup size?

Ok my question is simple. Lets say that when i click database and hover over shrink it says it can be reduced 1 GB space. Now when i do a backup of this database, does this space also getting added ...
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This query is choking the server. How can I improve it?

Following query is hogging a lot of resources, as much as that the queries are getting locked down & CPU usage goes through the roof! The MySQL Processes list shows that as the number of requests ...
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How to optimize this dynamic stored procedure

I have a stored procedure which is retrieving data using 20 tables. Sample of the procedure: CREATE PROCEDURE GetEnquiries ( @EnquiryDate DATETIME = NULL ) AS ...
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What are the best Database Analytics Companies for analyzing several 1000s or Mio. of products,sum them together and analyze them for statistics?

We will get several thousands products in our database. The problem is that one product can have several different names e.g. "iPad 16GByte UMTS schwarz" or "iPad 16GB 3G black" and so on. But they ...
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DB2 CASE statement faster with parentheses around entire WHEN

Trying to optimize slow queries, someone on my team come across this. Having this in our stored proc: CASE WHEN MYCOL BETWEEN @STARTNUM AND @ENDNUM AND RECTYPE = 'RO' THEN 1 ELSE 0 ...
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Do MySQL optimizations hold for MariaDB also?

I am a developer who will be starting a new project soon in which database performance will be crucial. The current candidate for the backend is MariaDB. I have worked with MySQL and MariaDB before in ...
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179 views

PL/pgSQL functions and optimizations fences?

I am newbie on DB stuff. And my DB knowledge is very old (around MSSQL2000). All what I remember is, the stored procedures are faster than ordinary queries because it avoid query compilation and ...
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342 views

What's the optimal server configuration for fastest inserting in a MySql database in this scenario?

I have a MyISAM table partitioned by range with 90 partitions representing the last 90 days. I expect this table to receive somewhere between 500 million to 1 billion records before i start rotating ...
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225 views

Query optimization with extreme statistic

I have a table: mysql> describe table_1; +---------------+------------------+------+-----+---------------------+----------------+ | Field | Type | Null | Key | Default ...
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How to optimize a log process in MySQL?

In my project, I have about 100.000 users and can't control their behavior. Now, what I would like to do is log their activity in a certain task. Every activity, is one record which includes columns ...
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can sql generate a good plan for this procedure?

I have read that procs that do not always do the same thing per se, will not always have a good plan generated. That is (correct me if I'm wrong), if I have a proc that if the day is even it reads ...
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How to setup mysql on tmpfs?

How to setup mysql on tmpfs ? I am reading a tutorial in french, where the author do it this way : 1.) Create a tmpfs directory : mkdir /var/tmpfs mount -t tmpfs -o size=1G tmpfs /var/tmpfs chown ...
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237 views

Optimizing queries against a set of tables that contain partitioned data

I have a third party program that creates and populates a series of tables to hold some historical data: data_33 -- contains data for 12/01/11 - 12/05/11 data_34 -- contains data for 12/05/11 - ...
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How to restructure this slow query containing subquery?

This query takes about 2-6 seconds to run depending which tag id(s) is/are selected: SELECT t2.id, t2.name, count(*) as kpl FROM (SELECT pt1.post_id FROM posts_tags pt1 WHERE pt1.tag_id ...
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1answer
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EXPLAIN ANALYZE shows no details for queries inside a plpgsql function

I am using a PL/pgSQL function in PostgreSQL 9.3 with several complex queries inside: create function f1() returns integer as $$ declare event tablename%ROWTYPE; .... .... begin FOR event IN ...
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189 views

When is mariadb creating tmp tables?

I have found, that copying to tmp table is taking most of the time of a slow query, that I wanted to optimize. I watched the output of 'profiling' in a terminal. This happens on a pics table with 6000 ...
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How to optimize this slow SQL query

I have a slow SQL query on my Drupal website and I don't know how to optimize it. Here is the query that Views produces: http://pastebin.com/StAEiXbY SQL fiddle: http://sqlfiddle.com/#!2/20081/1/0 ...
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Designating databases to certain CPUs

SQL Server 2012. AlwaysOn Cluster with two nodes, each has 4 cores We are consolidating SQL server instances and moving bunch of databases from various locations to a single cluster which has two ...
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1answer
183 views

Mysql Fragmentation. How bad is too bad?

I ran a table status for my companies production site and its showing close to around '49085939712' for just about every table in my database and we have around 400 tables. I am not a DB ...
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445 views

How do I calculate working business minutes?

I'm working on business inteligence reports and one of my task is to create reports for time tracking. I have to report on business minutes (10 hours per day) within business week (monday to ...
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4m Rows in MySQL, ~5 Minutes to Run Query

I have 2 tables, a users table and a log table which literally logs each time a user signs in. What I'm trying to do is grab a list of all users with a certain rank who have not logged in for over a ...
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MySQL query WHERE IN + ORDER BY, which EXPLAIN is better and how to avoid filesort?

This is my table definition, without any special index for now: CREATE TABLE `filter` ( `field_name` varchar(32) COLLATE utf8_unicode_ci NOT NULL, `category_id` varchar(32) COLLATE ...
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Query looks optimal but logical reads is huge

I run the following (really simple) query in SQL Server: SELECT MAX(PK_Field1) FROM MainTable kh WHERE kh.PK_Field1 >= '2014-12-01T00:00:00' AND kh.PK_Field2 = 1572 AND ...
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Simple SELECT takes forever, but works as a subquery. Why?

I'm running a MySQL 5.1 server and I have a MyISAM table called my_table with nearly 5 million records. Its structure is the following: ...
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mysql: need help to optimize my query/table

I'm wondering if someone could help me optimize my tables/query to speed up a query. It is currently running ridiculously slow. I think a well-thought out index could help me. Any help would be really ...
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Mysql Server optimization tips needed! (InnoDB)

I've recently been trying to optimize our mysql server but I've encountered some pretty serious problems on the way. We're running a game server which is coded in C#. We have two dedicated servers. ...
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Optimizing MySQL for Read-Only?

We have 14 GB worth of CSV's which total 138 million rows. I imported this into a MySQL table first with InnoDB, and then tried again with MyISAM. In both cases, a simple SELECT on primary key ...
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114 views

How can I find out which statistics are evaluated by the optimizer?

My enterprise has a farm of many nearly-identical, isolated production environments. Each environment has a SQL Server 2005 database server, each supporting a database with nearly identical schemas. ...
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Understanding optimisation of complex SELECT queries

I have a people table with basic contact info in. I have a bunch of criteria that can select Id values (fields called pid) from the people table. I want records that match ((criterion 1 or criterion ...
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How to search for an ID and its descendants in this query?

I have the following tables: Project Unit ------------- --------------- ID | IDUnit ID | IdParent I have to select all projects that have the IDUnit ...
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MySQL query 'going away' on executing INSERT ON DUPLICATE UPDATE statement with a 12524 character blob

I have a mysql insert on update query like so insert into table (col1, col2, col3) values (1,2,'huge blob with 12524 chars') on duplicate key update col3 = 'huge blob with 12524 chars'; col1, col2 ...
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Why does MySQL use all of memory and goes into swap when doing lots of delayed inserts?

We have a database server running Centos 5.6 64bit 64Gb of RAM. The server is idle most of the time. However, every hour it gets a lot of DELAYED inserts. Up to 3 mil INSERTs per hour into a MyISAM ...
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Why the stored procedure is much slower than a temporary table? [closed]

I want to do the updating of my database every day and I will like to use stored procedures but the time of execution of the temporary table is faster than the stored procedure. How can I optimize my ...
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Is it possible to get seek based parallel plan for distinct/group by?

An example from this question shows that SQL Server will choose a full index scan to solve a query like this: select distinct [typeName] from [types] Where [typeName] has a non-clustered, ...
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Slow transactions, many locks

At high load conditions the server app stops responding to client because begin/commit statements are executing very slowly (some take 15 seconds). The queries are simple - insert, update two columns ...
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Tagged questions

I have similar to StackExchange network that utilises tagged questions. In my web application Users also can find questions by tags. The query below returns a set of tagged questions: SELECT ...
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Mysql - show results from 3 tables excluding NULL or EMPTY values for certain fields

I have 3 simple tables with polls, users and votes. I'd like to show all polls ordered by clean count of votes (sometimes either poll_id or user_id don't get inserted). Furthermore I'd like to show ...
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Why the WHERE clause is not pushed down in the view's query?

With Postgres 9.4, I'm doing the following query quite often: SELECT DISTINCT ON(recipient) * FROM messages LEFT JOIN identities ON messages.recipient = identities.name WHERE timestamp BETWEEN timeA ...
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Why isn't oracle using an index for distinct query ?

This is the scenario SQL> exec dbms_stats.gather_table_stats(user,'TM', cascade=>true) PL/SQL procedure successfully completed. SQL> SELECT SEGMENT_NAME , SEGMENT_TYPE , BYTES / 1024 / ...
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Why does adding LIMIT to my query make it crawl?

Simple query: select sum(score) total,name,gender,dob,country from users join scores on users.id = scores.user_id where date between '2012-01-01' and '2012-01-31 23:59:59' group by scores.user_id ...
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Optimizing a Postgres query with a large IN

This query gets a list of posts created by people you follow. You can follow an unlimited number of people, but most people follow < 1000 others. With this style of query, the obvious optimization ...
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Is there any command to optimize all MySQL tables one by one automatically?

I execute below command line statement to optimize a table: optimize table tablename; Is there any command or statement which can optimize all the tables one by one of the selected database?
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Changing ORDER BY direction causes performance issue

I use MySQL 5.6, and I have two tables each with 16M rows: CREATE TABLE IF NOT EXISTS `newsstudios` ( `id` int(11) NOT NULL AUTO_INCREMENT, `title` varchar(255) COLLATE utf8_unicode_ci NOT NULL, ...
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Trying to optimize query for performance (MySQL)

So I have this table that has a lot of foreign keys but when I will a record, I need to join all on those tables because I generally need those fields for the record to make any sense. The basic ...
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Optimizing query using a WHILE statement

I'm trying to convert a view that extracts a yearly amount into something more WHILEish The query is more or less: SELECT * FROM (SELECT SUM(EmployeePaid)*2 AS Total2013 FROM TblRecords WHERE FYear ...
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Threshold for sort spill and random cardinality estimates

I wanted to test tempdb spill warnings so I run the following script on SQL Server 2014: USE tempdb IF OBJECT_ID('tempdb..tblTest') IS NOT NULL DROP TABLE tblTest CREATE TABLE tblTest ( ...
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Optimize a query on two big tables

I have a very important query in my system that is taking too long to execute due to huge amount of data on tables. I'm a junior DBA and i need the best optimization I can get for this. Tables have ...
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Will OPTIMIZE TABLE have any impact on my data?

I'm having issues with a database that is getting quite slow. The analyzer in phpMyAdmin recommends that I run OPTIMIZE TABLE on my tables. But before doing so, I would (of course) like to know if ...