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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Slow insert with MySQL full-text index

I use a full-text index in a MySQL table, and each insert into this table takes about 3 seconds. It seems that MySQL rebuilds (a part) of the full text index after each insert/update. Is this right? ...
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46 views

Postgres: Is migrating old records to separate table and creating new aggregated records a good strategy to improve search speed?

I have a table with 1M+ records. New records are created and updated each day each time an event occurs for each type of event (which there are many). I frequently need to find sums across many ...
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2answers
194 views

How to optimize indexes on MySQL query with various sorts

I have an INNODB table levels: +--------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
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2answers
129 views

mysql multiple column index Cardinality order

How does Multiple-Column Indexes work in MySQL? How is it stored internally? consider a table with Multiple-Column Indexes on two columns (X,Y). If X has High-cardinality than Y i.e., X is less ...
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4k views

How to force higher values of open_files_limit or table_open_cache?

I'm having a frustrating problem where setting my.cnf to values higher than I currently have them does not 'take'. This is MySQL 5.6.14 on MacOS X 10.8.3 I'm trying to address dropped connections ...
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29 views

Optimization for query n increase performance

I am executing the following query: select count(inspection_result) from table where (inspection_time between "2015-06-28" and "2015-07-04") and inspection_result= 1 and part_type = "39000048" and ...
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382 views

MySQL: Optimize query with a range and distinct count

I have a query on a large table with millions of rows that looks like this: SELECT COUNT( DISTINCT clicks.tx_id ) AS unique_clicks_count , clicks.offer_id FROM clicks WHERE ...
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2answers
82 views

SQL Server 2008 R2 Memory Pressure

My SQL Server has a weird problem. It seems it happens with the same matter. It always restarts after running a period of time(about one month long). And I used dbcc memorystatus to check the problem. ...
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287 views

mysql fulltext query is very slow

I have one table for User detail in MySql with about 500000 records in it. I have also created fulltext index on firstname, lastname field on this table. but when I am trying to search any single ...
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1answer
192 views

How to determine cost/benefit of adding an index?

According to Craig Ringer: While it's usually a good idea to create an index on (or including) your referencing-side foreign key columns, it isn't required. Each index you add slows DML operations ...
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2k views

mySQL Optimization Suggestions

I'm trying to optimize our mySQL configuration for our large Magento website. The reason I believe that mySQL needs to be configured further is because New Relic has shown that our SELECT queries are ...
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63 views

How can i update my database from another database using temporary tables?

I want to update tables of my database using another big database every day with using temporary tables and without returning result. How can i update it? This my temporary table : use data_pro; ...
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671 views

INSERT take too much time

I have in my MySQL DB a few tables Most of the time, I'm only doing INSERT in my db. I have up to 4 connections to the DB, each one inserting into a different table. There cannot be two connections ...
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71 views

Why the stored procedure is much slower than a temporary table?

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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132 views

Optimization of an Oracle query

I have a view which is accessed via DBLink in Oracle. This view is made up of different tables. Now we have to execute queries on this view. Example: Select * from Viewname@dblink where ...
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243 views

Modification to GEQO (Genetic Query Optimization) of PostgreSQL

I need to implement a functionality that is in line with the GEQO functionality of PostgreSQL. I understand that GEQO approach is to encode query plans as integer strings and GEQO generates these ...
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45 views

How can i add index in MYSQL stored procedure?

I can not use alter table () on my stored procedure i don't have a permission to do that in the big database data_pro. How can i use index in my stored procedure for my 2 fields in where condition? ...
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1answer
130 views

Why is my stored procedure very much slower than the same MYSQL query?

My stored procedure is very slow compared to a normal query or a temporary table. How can I optimize my stored procedure? CREATE DEFINER=`datasll`@`...` PROCEDURE `product`() BEGIN EXPLAIN ...
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2answers
128 views

Slow Performance caused by Correlated Sub-queries & Clustered Index Seek

I'm running a query in which one of the tables (FIELDDATA) has nearly 400,000 records which is taking more than 2 minutes to execute. I ran the execution plan, and noticed that the clustered seek ...
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3k views

Optimize IN clause in where query with order by - MySQL

I am trying to optimize a query that using IN clause in WHERE to avoid file sorting. To make it easy , I created the following sample which shows the problem. Here is my query: SELECT * FROM `test` ...
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61 views

Why my sql query run faster than my stored procedure?

I am trying to write a script in MYSQL Workbench to update my database every day using stored procedure but I find it too slow compared normal query or temporary tables. If i use temporary table the ...
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2answers
73 views

Is there's another function to optimize this query in MySQL?

I want to use a function that returns for me the same result in one line is that's possible?? MIN( CASE WHEN (data.pro LIKE '1 %' ) THEN 1 WHEN (data.pro LIKE '2 %' ) THEN 2 ...
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1answer
182 views

getting “table is full” error even if the table size is much smaller than tablespace

Currently I am using MySQL NDBCluster 7.3.5. I have created one UNDOFILE hhme.dat with INITIAL_SIZE=200m. Also one tablespace hhmefep_tbs with DATAFILE hhmefep_tbs.dat having INITIAL_SIZE=500M ...
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1answer
153 views

Optimize large table design

First, I am a complete novice when it comes to databases, but have been given the task to speed up queries on a large set of data. (Hundreds of millions of records) The current implementation is a ...
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1answer
60 views

How to optimize this MySQL query?

Hi can someone help me to optimize this MySQL query, it's taking very long to complete, I have set indexes correctly, but it seems that string operations are slowing this query SELECT ...
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462 views

Optimising a query of an SSRS dataset

Consider the query given below: SELECT * FROM ((SELECT c.cust_id , c.username , REPLACE(qs.seg_type_ref_key_02, 'N/A', 'Non Vip') casino_group, ...
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63 views

Is LIMIT processed before or after retrieving data?

MySQL. My heavy query crashed our MySQL server. If I add LIMIT 10 will it make my query more lightweight? (both for indexed and unindexed queries). Which way LIMIT are processed: before the rest of ...
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73 views

Optimize table by removing large field

I have a MySQL table of articles. It's growing rapidly, and over 50% of the size on disk is accounted for by the article body field, as you might expect. There are no indexes on the body, but 8/16 ...
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374 views

How to improve the performance of SELECT queries with multiple JOINs on a 50GB database hosted on AWS m3.medium MySQL RDS?

Example query: SELECT p.ListAgentEmail, p.ListAgentFirstName, p.ListAgentLastName, p.ListingKey FROM Property_RES AS p INNER JOIN Property_RES_COUNTIES_OR_REGIONS ON ...
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6answers
35k views

How to determine if an Index is required or necessary

I've been running an auto-index tool on our MS SQL database (I modified a script originating from Microsoft that looks at the index statistics tables - Automated Auto Indexing). From the stats, I now ...
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32 views

Optimize query with access to tiny fraction of data

I am trying to optimize some queries but I can only use a tiny portion of the actual data they will be executed against later. Probably the query optimizer will generate completely different plans ...
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2answers
5k views

How to optimise T-SQL query using Execution Plan

I have a SQL query that I have spent the past two days trying to optimise using trial-and-error and the execution plan, but to no avail. Please forgive me for doing this but I will post the entire ...
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1k views

Using something better than UNION for combining multiple queries

I have one big query which is based on 12 smaller queries that I have put together using UNION. A relative simple example of my query: (SELECT 'type1' AS 'type', fieldOne AS someField, ...
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38 views

Which query performs better when searching a row where a column has maximum?

Consider a simple table for example purposes: person(name varchar, age int) I have a task to retrieve the oldest person. Which query is better in general for such problems? Query 1: criteria with ...
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716 views

Best book on query optimization, rewriting, refactoring [closed]

I have a specific problem: huge amounts of Web-related data in Postgres db. The queries running against the data are often very inefficient. But in a more general sense, I need a book that explains ...
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56 views

Link-table(s) vs Redundant Columns? [duplicate]

Possible Duplicate: Would it be considered as a bad practice to have multiple nullable FKs on a table in SQL Server I have two tables, Users and People, both of which share a common ...
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1answer
23 views

optimizing mysql query using explain

I'm trying to optimize a query for a client; I'll try to describe what I'm going for at a high level before diving into the structure. The client database has a table of transactions (currently ~352k ...
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1answer
73 views

Optimizing a query that performs worse on a smaller dataset

I am trying to run this query. The * is just for simplification, I'm selecting ~10 specific fields for some calculations. SELECT * FROM `orders` LEFT JOIN `orders_processed` ON ...
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2answers
40 views

Sqlite query slow whilst it should be fast

I have the following query: SELECT breakType,date,blockname,modname,metadata,nbtdata,x,y,z FROM BlocksBrokenByExplosion WHERE dimension=0 AND y>60 AND y<70 AND x>150 AND ...
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SQL Server Baseline and Performance Optimization

I've been struggling a little bit around Performance Troubleshooting including baseline and troubleshooting of SQL Performance. Could anyone help with this or point me to where I can possibly get a ...
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2k views

How can I better optimize my tables and a LEFT JOIN query to find items that don't yet exist in the right table?

I have two tables that represent a list of urls and their related word indexes. Here are the table definitions for reference. desc urllist; ...
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51 views

Having four different tables or having one table with one more field?

I have a website with 4 translation (That is Arabic with 4 different Persian translation), and I had exported each of these translations to different tables. Which one of these ways are faster and ...
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87 views

Will the Oracle optimizer still plan a join if I'm not reading any columns in the joined table?

Suppose I have the following view: CREATE VIEW dummy AS SELECT a.some_column, b.other_column FROM a LEFT JOIN b USING (key_column); When I do a SELECT some_column FROM dummy, is there a way to ...
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170 views

Vertica pagination

I have a query that gives the total number of rows to use in a pagination: select count(1) as total_rows from (subquery with some sum() and 2 inner joins) as as total_sums ; when I run only ...
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1answer
740 views

Are there any disadvantages to partitioning on financial year?

Our current set up has one table per financial year (May 1- April 30). Each table has approx 1.5 million rows. We have about 8 years of data, and will obviously be adding each year. The majority of ...
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2answers
66 views

Mysql Index for concat select

For Below Query SELECT MAX(CONCAT(date, ' ', last_entry)) AS LAST_LOG FROM entry_log WHERE TRIM(LEADING 0 FROM card_no)='2948' I've index on date card_no date,last_entry ...
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40 views

How to determine if an Index is uselss in Percona MySQL?

Using Percona Server 5.5 I've a table which stores user activty (lets call it user_activity). It was created quite a few years ago when I had only a little bit of knowledge about database ...
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98 views

Optimizing queries on a range of timestamps (one column)

I am using Postgres 9.3 through Heroku. I have a table, "traffic", with 1M+ records that has many inserts and updates every day. I need to perform SUM operations across this table over different time ...
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44 views

Storing small array of many possibilities

Let's say I need to store the text of a series of books, line per line in a database, and present them in a (CMS-based) website. I thought the correct setup would be: a 'library' table: containing ...
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56 views

How to most efficiently store possible combinations of categories?

I have a table of categories (currently with 14 rows, not likely to change). A need to cache combinations of categories emerged, so I'm creating a table of allowed combinations (only few hundreds of ...