A class of issues where a database executes a query inefficiently due to the optimiser selecting an innapropriate query plan.

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how to improve query performance

## Only 1 query which returns 10 rows. ## It took about 66 secs mysql> explain SELECT al.log_id , al.user_id , al.page_name , al.section_name , al.submit_time , al.url , ...
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1answer
131 views

How to know what to investigate and how for a VERY slow stored procedure

I have inherited a large and slow stored procedure and it's giving me a nightmare: I'm not a DBA, although I have some knowledge, but I don't know where to start to identify this bottleneck. I have ...
2
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3answers
273 views

How to get all non deleted messages from one user

I have two tables one for messages called default_messages and the other for recipients called default_recipient. This is how SQL for those table looks like: CREATE TABLE IF NOT EXISTS ...
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2answers
1k views

How expensive are SELECT FROM LIKE statements from a design perspective?

I have a situation running out of control regarding an ever increasing number of small static files I need to access randomly in a large directory structure. I MUST reduce the number of those files ...
2
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1answer
345 views

Oracle ash report

Recently, i have been handed over with an ash report from DBA. To me this report is like french. I have no idea what it is about and what all is written in this report. Can someone please guide me in ...
2
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1answer
58 views

How to speed up select distinct?

I have a simple select distinct on some time series data: SELECT DISTINCT user_id FROM events WHERE project_id = 6 AND time > '2015-01-11 8:00:00' AND time < '2015-02-10 8:00:00'; And it ...
2
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3answers
79 views

Change table scan in query plan to seek

I have an ORM generated query (Django) running against a local Postgres 9.1.11 instance that looks up ~5 records from two specific match fields. Due to the nature of the EDI load program, I need to ...
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2answers
5k views

Why can't we access SQL Server when a long query is running in Management Studio?

We have a SQL Server Database (2012 Standard edition). The database is accessed through an ASP.Net web page which displays the count of databases in different tables on page load. This work fine ...
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1answer
141 views

How to optimise window queries in postgres

I have the following table with approximately 175k records: Column | Type | Modifiers ...
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1answer
160 views

Select data based on records created_at column

I have two tables Keywords, ProjectReports: http://sqlfiddle.com/#!15/06ae3/1 As you can see in that example everything works fine, but I want to get more data from those 2 tables and I don't know ...
2
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1answer
261 views

Why would a query in code be slower than a query in a SQL tool

When we face performance issues with out application, one of the first things we do is try to isolate if the problem is the code, the queries or the database itself. The most frustrating part of this ...
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2answers
1k views

Is there a difference in performance between @date and getdate()?

Usually I use the getdate() function in my where clauses to go back in time. Something like: DOC.DATUM >= DATEADD(DD,-1*SSN_SDO.DANA_ZA_POVRAT,GETDATE()) Will SQL Server 2008R2 perform faster ...
2
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1answer
297 views

Parameter triggers different execution plan, but why?

I have a table CREATE TABLE [dbo].[Numbers] ( [Date] [date] NULL, [Time] [time](3) NULL, [Value] [char](10) NULL ) and the table has > 10 Billion rows, therefore it ...
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1answer
976 views

How to speed up mysql query?

I have query : SELECT `school`.`ARCO_name`, `student-`.`ClassSize_7`, `student-`.`ClassSize_8`, `degree_o`.`degree_code`, `accredit`.`full_faculty_3`, ...
2
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1answer
81 views

Unused index in range of dates query

I have a query that is not using existing indices and I do not understand why. The table: mustang=# \d+ bss.amplifier_saturation Table ...
2
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1answer
44 views

How can I speed up an sql query that round trips between two tables

I first posted this question on stackoverflow, and now I see this site, seems more relevant. These tables are not that big, but the time taken to process this query is long. What can I do with the ...
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2answers
427 views

SQL Server - Logical Reads lowered, Execution time remained the same

A view executed Select columns from view where col= "date range" (view contains calculation in it Col1+Col2*col3 AS Col4). It took 7 seconds for 500K rows to return, logical reads some 144k. Added ...
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2answers
460 views

Super simple mysql query taking too long

I have the following: SELECT * FROM autorepair WHERE zip_code IN (91316,91356,91416,91426,91436) AND specialty = 'transmission' ORDER BY ABS(91316 - `zip_code`) LIMIT 0,10 Indexes: -zip_code ...
2
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1answer
164 views

Query returning unused stored procedures

When I run SP_askbrent@asof = '2014-05-20 16:00' a period where the database was timing out, I'm getting dozens of CREATE PROCEDURE xxx entries. When I run the following query, the results show the ...
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1answer
44 views

Will composite indexes or unique indexes help with query performance?

I need help with identifying indexes to increase performance of the following query. I'm currently using v5.5 with InnoDB. I cannot modify the query. However, I can add indexes as needed. The ...
2
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1answer
43 views

General purpose view for last value in a group

I am trying to create a view to show the last value in the group. Looking for a more general purpose query. CREATE TABLE a ( id INTEGER, seq INTEGER, val VARCHAR2(16), PRIMARY ...
2
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1answer
457 views

MySQL: What is the most optimized way to use datetime type field in query

I am working on optimization of some slow queries in my application. I found a query in which datetime comparison has been used. Below is the subquery: select * from jos_content c where c.visible = 1 ...
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2answers
118 views

Convert to Self JOIN

I have a correlated sub query, which is taking 16 Minutes to execute. How can I convert it to join or optimize it. SELECT SSF.SM_StockCode, SSF.ST_ItemSize FROM Stock AS SSF WHERE ...
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2answers
311 views

Trigger update does not seem to finish

I'm new to PostgreSQL triggers & functions and such. I've got a table: keywords and each keyword should be unique. So when I try to insert a keyword that already exists, it should simply update ...
2
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1answer
136 views

Are there differences in performance of getting data between FullText Search and indexed columns

In SQL Server 2008 R2 I have a query which looks like create stored procedure give_me_art @filter varchar(15),@skl_id int begin select id,naziv,sifra,isnull(lager.kolicina,0) as lager from art ...
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2answers
406 views

Efficient way to query set of rows from MySQL

I am using MySQL database engine. My Java application uses simple JDBC to retrieve data from database. I have following database schema: main table with two columns: (INTEGER id, BLOB data). id is ...
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2answers
3k views

How do I force a JOIN to use a specific index in MySQL?

I have a query that JOINs 2 tables; lineitem and part, select sum(l_extendedprice* (1 - l_discount)) as revenue from lineitem force index for join (l_pk), part where ( ...
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1answer
586 views

inner join on PK with extra criteria slow despite indices?

Given the two tables below I am struggling to understand: why is the third query slow even though first two queries are fast what exactly is EXPLAIN saying can I do anything to significantly speed ...
2
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1answer
140 views

Combining columns in index

With reference to RolandoMySQLDBA's answer on MySQL: Index when joining to tables not being used (Performance optimizing question) He mentioned Make sure you build an index that involves the ...
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1answer
102 views

Optimising query on view that merges similar tables with a clear discriminator

Using PostgreSQL 8.4, I have a number of tables that have a very similar structure, but that belong to different categories: CREATE TABLE table_a ( id SERIAL PRIMARY KEY, event_time TIMESTAMP ...
2
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1answer
520 views

Should I use left join to do my job in this scenario?

What I want to do is to find out the items which appeared more than once in this table: mysql> desc tables; +-----------------+---------------------+------+-----+---------+-------+ | Field ...
2
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2answers
125 views

CPU or Page Reads

While comparing query performance should i go for CPU values or Page Reads. On live server (with better hardware) a query is showing different CPU when i test it on my local machine. But Page Reads ...
2
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1answer
1k views

postgres composite index design

In my rails application using the Postgres database, I have a table called tw_schedules which belongs to a scenarios table (one scenario to many tw_schedules). In addition to the scenario_id foreign ...
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1answer
1k views

How to optimise read/write performance a MySQL table with many rows?

I am developing a django application where I use a MySQL database. In my application there is one table for domains information which has only 2 coloumns id domain_name but I have a problem when I ...
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1answer
258 views

Query tuning - SQL Server

One of our developers are trying to run the below query on a development server, which involves pulling data from a linked server, production. The query ran for more than 14 hours before it was ...
2
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1answer
155 views

MySQL optimization question — how to speed up a simple query

I have a very simple database, one table with five columns (one INTEGER key, two VARCHAR, a DATE, and a DOUBLE). The table contains 909,000 records. A simple query like SELECT t.price FROM ...
2
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2answers
58 views

Slow queries on production Server

I am a developer who has been asked to look at a database slowness issue. I have had a look at the waits on the server and retrieved the following using a query from Red Gate's wait stats white paper. ...
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2answers
93 views

Joining two Mysql VIEWs takes a very long time

I have a textbox (for which I used jQuery auto-completion) in my PHP form where user can insert an actor/actress name and then by clicking "Search" button, a new window is opened showing list of ...
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1answer
68 views

Running a query on an improperly indexed, 600gb table

This is my first post on here and I'm really baffled by this. I have joined a team and somewhere in the past a horrific table was created which has been bloated to a point of 600+gb of data. ...
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1answer
281 views

Extremely long query time after upgrading to Postgres 9.3 from 9.1

We're attempting to upgrade from Postgres 9.1 to Postgres 9.3 on a FreeBSD 9.2 zfs box. Performance is noticeably slower across the board, but we have one query that has gone from 353ms to >200000ms. ...
2
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1answer
227 views

Improve select query performance

The following select query from my application is taking more than 200ms. The table has around 2 million rows. Is there any ways to improve the performance of this query ? select count(id) from ...
2
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1answer
489 views

T-SQL Query runs quickly on local PC, but slow on SQL Server?

I have a query with a few joins and a couple of basic SUM(...) statements, and no parameters. It's been running without issue for months - but has suddenly started running very slowly on the server ...
2
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4answers
6k views

How can I query data from a linked server, and pass it parameters to filter by?

I have a really big query that needs to be run on multiple databases, and the results appended to a temp table and returned. The basic syntax looks something like this: INSERT INTO #tmpTable (Id, ...
2
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1answer
59 views

What is the algorithmic complexity of a PosgtreSQL greater than or lesser than index query (compared to equality)?

Assuming there is an index idx_int on an int_col column, what is the algorithmic complexity of a query like this? SELECT id FROM table WHERE table.int_col > 1; I'm specifically interested in ...
2
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3answers
483 views

Why is SQL running the same query longer from another connection? [closed]

Here is the issue overview: Why does my stored procedure run faster when executed localy vs remotely? Dont jump to any conclusion just yet, let me explain what I mean... Here is the setup: A Windows ...
2
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1answer
333 views

Slow query performance

My database contains 20,000 rows and the following query is slow. Please help me to speed this up: SELECT r.report_id, r.user_id, u.user_name, u.user_mail, ...
2
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1answer
879 views

Oracle 10g using collection with sql

I have a stored procedure that takes collection of objects. (TABLE OF MyCustomType). Inside the procedure I'm trying to join this parameter with real tables. For example, something like create or ...
2
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1answer
709 views

oracle merge operation hangs (or loops); query tuner claims it's a cartesian product operation

I have a Merge query (open to better suggestions) that seems to cause the server to hang. (I'm not sure what it's doing, but it pegs the CPU and never completes) When I run it through the query ...
2
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1answer
106 views

Get the id_user_app if not exists in id_user_rq

I'm building a application and have this table for users relationships. I need to build some queries like for example: Who invited me as a friend? Who I invited to be my friend? Who I accept as ...
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1answer
744 views

How to calculate query that access system view cost in Oracle?

For a query that returns if there are any active transactions within current session , SELECT COUNT(*) FROM v$transaction t INNER JOIN v$session s ON (t.ses_addr = s.saddr ) INNER ...