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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SQL Server 2012: query to see queries that are consuming more resources [duplicate]

I'm trying to find/build a query to show me those queries that are consuming more resources in SQL Server so that I can optimize them or at least have a statistical idea of what is really happening. ...
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144 views

Incorrect unit allocation size. error comes when Tuning the Database

Here I am Using the SQL IDERA tool for checking the Index and performance of the Database, then i found below error, can any one tell what is it talking about. Incorrect unit allocation size. ...
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48 views

Can an index be added to a PRIMARY with a null key?

I have a query that takes a long time to return, roughly 12-15 seconds, which I'd like to optimize. The query below is the result of running the original query with SHOW WARNINGS. If I run EXPLAIN ...
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31 views

How can I optimize a query with multiple left joins?

The working example that I have been provided with takes about 20 minutes to fully process. http://paste2.org/G8BZvNHe What are some basic strategies for making this more efficient? Edit: I've ...
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2answers
742 views

What indexes should one use to optimize a PostgreSQL query with a JOIN depth of 2?

Disclaimer: I am relatively new to PostgreSQL. I'm wondering how to optimize a query that does 2 INNER JOINs. My scenario is fairly simple: Select Posts with a photo (Posts.photo IS NOT NULL) and a ...
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29 views

Creating separate small table from big based on access frequency for “select” performance

I have table with several millions of rows which are selected a lot (many times in a second in average). It is indexed and everything is ok for now. But performance is always a question (sometimes ...
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2answers
171 views

Slow subquery in SELECT statement

Having tried many different methods, I can't get my query taking shorter than 40 seconds to run with a dataset of ~11000 rows. The table is a list of hotel bookings, containing (most relevant) ...
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2answers
300 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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2answers
452 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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2answers
1k views

Can rebuilding indexes cause worse performance after the rebuild is finished?

We have a customer database that is heavily fragmented - practically every table with more than 1000 pages has >95% fragmentation. Fill factors are set to sensible values, but page space usage is ...
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2answers
65 views

Get the pais_id not associated to fabricante_distribuidor_id and producto_solicitud_id, the opposite from SELECT query

I have this query for get all the pais_id given a fabricante_distribuidor_id and producto_solicitud_id, the query works fine. SELECT DISTINCT nom.pais_id FROM negocio.fabricante_producto_solicitud ...
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49 views

optimizing a select query of 1.5 million entry

I have the following query: SELECT s0_.id, s0_.lowresimageurl FROM app_instagram_shop_picture s0_ FORCE INDEX ( idx_deleted_shopId ) LEFT JOIN app_instagram_shop s1_ ON s0_.shop_id = s1_.id AND ( ...
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1answer
64 views

MySQL column type to boost performance

I'll have a table where: userid (link to user's id in users table) foldername (a varchar, max. 260 char) entry (varchar, max. 1024) data (varchar, max. 20kb) Single user will have several ...
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1answer
173 views

optimize design for a table with 50 columns [closed]

I have a table with 50 column and one of my friend has told me to split the table in 4 different table to save 12 column in each table. He proposed a design to have Master table and refer the PK of ...
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100 views

Large text column slows down whole table

I have a mysql database table table1 with a dozen columns in it. One column is a mediumtext column with lots of data in it and all the other columns are small (ints, timestamps, etc.). The presence ...
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1answer
190 views

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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425 views

Database design for price comparison site - too complex?

I'm working on a regular price comparison site with two exceptions. I want to show price history and also allow users to subscribe to a product with a specific size and color. As a result, I've ended ...
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101 views

Delete Query throwing warning db2

I am trying to delete multiple records from view The view has Instead of Trigger defined .. The view has records consolidated from multiple tables. [db2inst1@testServer001 ~]$ db2 "delete from ...
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340 views

How to Insert records from remote database to local database using dblink in postgresql 9.3

I have a scenario like i have a two DB, one resides in remote server and other resides local. Now i have to fetch the records from remote DB when new records are inserted on tables (in remote DB) and ...
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1answer
471 views

Why is the CTE much worse than inline subqueries

Im trying to better understand how the query planner work in postgresql. I have this query: select id from users where id <> 2 and gender = (select gender from users where id = 2) ...
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40 views

Create Temporary Index for bulk operation and Delete after its completed

I am moving bulk data to archive tables. Some times query returns up to 4.5million records, which takes about 2:15 minutes for a table of 40 columns. I want too increase the performance for the ...
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1answer
104 views

What would be most elegant way to replicate data contents periodically into a MySQL table?

I need to parse contents from an API route and insert into a MySQL database. The aim of parsing contents is to replicate the data from the API to my database table. I need to check API response every ...
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1answer
666 views

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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1answer
831 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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1answer
11k views

Sql server table insert performance optimization

Setting In a datawarehouse, I am joining a fact table to 20 dimensions. The fact table has 32 million rows and 30 columns. This is a temporary staging table so I don't have to deal with other users ...
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1answer
103 views

Simulate more RAM with SQL Server

Background: I'm in the process of optimizing a Data Warehouse style query with big dimension tables. The optimizer does not like to pick the typical star schema join plan at the moment. When I force ...
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1answer
54 views

If a database is in memory does it still need indexing?

INFO I'm following lessons on databases. We're learning about indices now. Question If big parts of a table are in the memory, would using a index still have benefits? My side I would assume ...
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37 views

optimize my query mysql

I have the following query: SELECT DISTINCT d.movieName, d.castName, d.movieImdbId, f.year, f.posterLink FROM director_movie as d LEFT JOIN film_info as f ON d.movieImdbId = f.ImdbId WHERE d.castName ...
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1answer
384 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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72 views

How to use max function in such condition?

My query is select * from guestuser union select * from olduser ORDER BY userid DESC LIMIT 1; Is that correct query to find last userid from different table have different userid? can i change ...
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56 views

Slow MySQL Query when Ordering

This query takes around 2 seconds when the order by is included, without the order it takes less than a tenth of a second. The field that is doing the sorting, qc_products.addedDate, is an index and ...
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1answer
135 views

SQL execution 2 seconds with LIMIT parameter, without only 0.2s why?

This is my query and I need to return only 12 rows, but it takes 2 seconds with parameter LIMIT 12 while it takes only <0.2 to process all ~600 results (without LIMIT 12 or with LIMIT 1200 for ...
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63 views

Table design for optimum performance

For example let's say I have to create a table called Employee with columns EmployeeID, Name, DOB, Address, DepartmentID[FK]. So I create the table as follows with a primary key and a nonclustered ...
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2answers
174 views

Simple query is slow on 4M-rows table

I have in production a MySQL table pageviews with 4M rows that records page views of users on posts. I need to know which posts a specific user have read, but this request takes up to 15 seconds to ...
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1answer
75 views

PLSQL using cursors or functions to query repeated data

Is it better to declare a commonly used lookup query as a package function or as a function (either returning rows or values or returning a sysref cursor)? Whats the difference? What are the best ...
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1answer
271 views

MySQL - OPTIMIZE TABLE for partitions

I would like to perform OPTIMIZE TABLE opearation , this table is a partitioned table. Which method can be better in this scenario: OPTIMIZE TABLE tblname; or ALTER TABLE tblname ...
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1answer
314 views

How to manipulate join order of PostgreSQL optimizer?

I am working on table join order optimization. While query processing, I want to get table join order generated by optimizer, and update it by using my own algorithm in PostgreSQL? How can I update ...
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4answers
184 views

DB performance vs replication

I am working on a db optimization (planing for future project growth) and need some help. Currently, every table is using uniqueidentifier as PK (clustered index) and we have high index fragmentation ...
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1answer
75 views

optimizing query for slow queries

I have this query in my slowqueries table which essentially is taking about 5-8 seconds to complete the query time: SELECT s0_.id AS id0, s0_.updated AS updated1, s0_.created AS created2, ...
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227 views

Performance tuning self-joining MySQL query

I asked a question recently on the correct way to update a table using multiple joins to itself in order to generate the desired values. Updating MySQL innodb table based on multiple joins After ...
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1answer
59 views

MySQL optimize range duplicate query

I need to eliminate duplicates from a time sheet. I found this solution and have adapted it for my own needs: DROP TABLE IF EXISTS `activity`; CREATE TABLE IF NOT EXISTS `activity` ( `id` int(11) ...
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221 views

Configuration help my.cnf Mysql

Is the following my.cnf file OK for a dedicated server with 56GB of RAM (on ubuntu server and 8 processors)? I'm running just one website on the server and there is a high demand on my cpu from ...
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0answers
126 views

How to optimize update using join in postgresql

I'm using PostgreSQL 9.3.5 on a CentOS system. I have a very large table (twenty million rows, 50+ column) that aggregates data from a few hundred systems. Several times a day each of the systems ...
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1answer
120 views

Optimizing SELECT queries

I'm not very experienced with database query optimization. I've been reading through similar questions here and Postgres tuning articles online, but unfortunately I haven't had any luck. Here's what I ...
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1answer
192 views

Is there a way to force one optimization level in SQL Server?

Based on Paul White's blog, there are three optimization phases in SQL Server, search 0(Transaction Processing), search 1(quick plan) and search 2(full optimization). Each phase has entry and ...
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2answers
2k views

Slow index scans in large table

Using PostgreSQL 9.2, I have troubles with slow queries on a relatively large table (200+ million rows). I'm not trying anything crazy, just adding historic values. Below is the query and the query ...
3
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1answer
242 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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1answer
856 views

Slow postgresql query with pagination and filtering

For the DB in question, I have followed the advice of Pagination Done the PostgreSQL Way That is, results are being paginated on a composite index with a definite sort order. Now, my problem is ...
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62 views

Oracle estimate cardinality on partitioned table

How does Oracle estimate cardinality on a partitioned table if the query gets the list of partitions from a subquery or a join? For example, if I have a query like this select * from ...
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1answer
37 views

Join Operation using index defined?

I need to optimize some queries with several joins. I plan to create some indexes for these queries. I am currently using MariaDB with TokuDB storage engine. Should I expect the indexes for the join ...