An evaluation of whether a system works well enough to be fit for purpose. Normally performance refers to the speed with which a system completes an operation or set of operations over time.

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SQL Server Cache Flush and Disk I/O

We're busy load testing an OLTP system we've developed in .NET 4.0 and runs SQL Server 2008 R2 in the back. The system uses SQL Server Service Broker queues, which are very performant, but we are ...
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2answers
151 views

A question on SARGability

I just need to confirm that I understand something correctly: I recently viewed an SO question in which a user posted an answer in Linq like: from p in db.table where p.column.AddMinutes(1) > ...
11
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1answer
3k views

noexpand hint for non-enterpise edition and performance

I have to use Indexed views to reach performance. As I can see from this comparison table standard edition does not support indexed views. But BOL says: Indexed views can be created in any ...
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3answers
2k views

Where is the INNODB Performance Leak?

I have a weird problem which I cannot seem to fix. I'm more an web programmer than a Server/DB Admin, so I hope someone here can help me. The Situation I am working on a system which handles a lot ...
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2answers
4k views

More CPU cores vs faster disks

I'm part of a small company so as usual covering a number of different roles. The latest of which is procuring a dedicated SQL Server box for our .NET web app. We've been quoted on a dual Xeon E5-2620 ...
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Placing Transaction Log on Separate Volume [solid state]?

Transaction logs are often isolated on a separate volume. The rationale for this practice, as I understand it, is that the transaction log's data is written sequentially -- and hard drives can execute ...
11
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2answers
58 views

Why do my Batch Requests increase when doing a Differential Backup

I have started doing some long-term tracking of various activities on our 2012 SQL Server and I have noticed an increase in Batch Requests during our incremental backups. To give an idea, normal ...
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409 views

Minimizing Indexed Reads with Complex Criteria

I'm optimizing a Firebird 2.5 database of work tickets. They're stored in a table declared as such: CREATE TABLE TICKETS ( TICKET_ID id PRIMARY KEY, JOB_ID id, ACTION_ID id, STATUS str256 ...
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13k views

How do you clear out all old query plans from within Microsoft SQL Server?

We have an off the shelf application that uses a Microsoft SQL database. Within this application we pick and choose various selection criteria for each report. This application then runs these ...
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1answer
1k views

Why adding SQL Server user to “Perform volume maintenance tasks” improves the speed of database resizing so much?

If I want to create 5GB database with CREATE DATABASE [test] CONTAINMENT = NONE ON PRIMARY ( NAME = N'test', FILENAME = N'E:\2012\test.mdf' , SIZE = 5529600KB , FILEGROWTH = 1024KB ) LOG ON ( ...
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729 views

What is retrieved from disk during a query?

Fairly simple question, probably answered somewhere, but I can't seem to form the right search question for Google... Do the number of columns in a particular table affect the performance of a query, ...
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3k views

PostgreSQL Index Caching

I'm having difficulty finding 'lay' explanations of how indexes are cached in PostgreSQL, so I'd like a reality check on any or all of these assumptions: PostgreSQL indexes, like rows, live on disk ...
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4answers
5k views

Help me choose a RAID level combination for a SQL Server 2008 instance

I am going to rebuild one IBM 3400 server from scratch. This server is dedicated to a SQL Server 2008 instance running on Windows 2008 R2. I am going to make new RAID configuration. I have 6 SCSI ...
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3answers
3k views

Testing stored procedure scalability

I have an email application that will be called upon to deliver to the UI the number of new messages for a given user on each page load. I have a few variations of things I am testing on the DB level ...
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2answers
448 views

@table_variable or #temp_table

I have a big user defined table type variable that has 129 columns. I will store around 2000-3000 records in this table variable at a time and pass it to various stored procedures and functions to get ...
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1answer
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Why are multiple COUNT faster than one SUM with CASE?

I wanted to know which of the following two approaches is faster: 1) Three COUNT: SELECT Approved = (SELECT COUNT(*) FROM dbo.Claims d WHERE d.Status = 'Approved'), Valid ...
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2answers
1k views

How many Sproc Parameters is too many?

I've just started writing a Stored Procedure in SQL Server 2008 and have 30+ parameters. I've never written one with more than ~10 parameters, and that got me thinking... At what point are there too ...
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6answers
4k views

What could be causing strange query timeouts between PHP and MySQL?

I am the senior developer on a Software-as-a-Service application used by many different customers. Our software runs on a cluster of Apache / PHP application servers, powered by a MySQL backend. On ...
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2answers
3k views

Is there a way to force an index to stay in memory with SQL Server 2008?

I've got a table with several millions rows, from which I need to run some queries from time to time. First query will usually be quite slow (around 10s), and subsequent queries are usually way faster ...
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2answers
9k views

SQL Server Join/where processing order

After reading Slow SQL query, not sure how to optimize, it got me thinking about the general performance of queries. Surely, we need the results of the first table (when other tables are joined) to be ...
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3answers
325 views

Query Performance Tuning

When you finish writing a query/stored proc/function, what's the most informative way to quickly get some performance parameters? Do you run the query and view the actual execution plan? If so, what ...
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3answers
6k views

Database suggestion for a social network/ knowledge base community?

I am looking into various database types and DBMS's for a new project I am wanting to start in the summer. I have built systems in MySQL and postgreSQL , now I am wanting to expand my knowledge and ...
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2answers
18k views

Efficient query to get greatest value per group from big table

Given the table: Column | Type id | integer latitude | numeric(9,6) longitude | numeric(9,6) ...
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2answers
1k views

Strategy to handle an SQL Server DB with too many files (BLOBs) in it?

Scenario: SQL Server 2005 database servicing an ASP.NET application (on a separate web servers). Database: DB has about 5GB of "normal" data in it, and about 15GB of "files" (e.g.: a 200k PDF stored ...
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2answers
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Postgresql 8.3: Limit resource consumption per query

I'm using PostgreSQL 8.3+PostGIS 1.3 to store geospatial data on Ubuntu 8.04 Hardy. This particular version of PostGIS has a bug when calculating a buffer() on very complex segments, which causes ...
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185 views

Why is query thousands of times slower with DESC?

I have a PostgreSQL database (AWS RDS) and ran the following queries in psql: livenet=> EXPLAIN ANALYZE SELECT * FROM outputs ORDER BY height LIMIT 10; Limit (cost=0.57..36.82 rows=10 ...
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Inclusion of ORDER BY on query that returns no rows drastically affects performance

Given a simple three table join, query performance changes drastically when ORDER BY is included even with no rows returned. Actual problem scenario take 30 seconds to return zero rows but is instant ...
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2answers
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Which performance counters can you look at on a SQL Server Instance to determine it's performance and over all health?

I am a student from Fontys University in Eindhoven, and I am currently carrying out a series of interviews to help with the development of a SQL Server tool and I would like to get feedback from the ...
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2answers
10k views

Improve performance of COUNT/GROUP-BY in large PostgresSQL table?

I am running PostgresSQL 9.2 and have a 12 column relation with about 6,700,000 rows. It contains nodes in a 3D space, each one referencing a user (who created it). To query which user has created how ...
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4answers
57k views

High CPU usage on SQL server - Slow queries [closed]

Our MS SQL Server is using about 95% of the CPU-power. After a server (hardware) restart, or a SQL-Service restart, the usage is 0% and slowly increases over the course of 1-3 days. Depending on how ...
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3answers
11k views

How do I best measure the query performance?

I have 2 stored procedures, where the second stored procedure is an improvement of the first one. I'm trying to measure by exactly how much that is an improvement. 1/ Measuring clock time doesn't ...
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4answers
2k views

How can I optimize this MySQL query further?

I have a query that is taking a particularly long time to run (15+ seconds) and it is only getting worse with time as my dataset grows. I have optimized this in the past, and have added indices, ...
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1answer
2k views

How important are transaction log VLFs for performance?

How important are VLFs when considering database performance? What would describe an optimal situation for VLFs?
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550 views

How to implement paging in an effective way?

I have a database query which could result in a big result set. The client which displays the data receives the data over network, so the idea was to minimize the amount of transferred data by ...
9
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1answer
296 views

Estimating IO Requirements for Bursty Usage

We have an application that queries a SQL database periodically throughout the day. There are periods of zero or only light activity, interspersed with individual requests for relatively large ...
9
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3answers
14k views

Cache MySQL database in memory

I am having problems with a website with 600MB of MySQL database. The website is way too slow. I noticed the bigger the MySQL database gets, the slower it goes. When it was 5MB, the website was very ...
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4answers
18k views

How to get the most out of MySQL on a QuadCore machine with 16 GB of RAM?

I'm running a MySQL 5.5 server on my workstation for scientific data analysis and wonder how to configure MySQL in order to get the most out of it performance-wise. The types of query that I typically ...
9
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1answer
9k views

Auto Update Statistics in SQL Server 2008R2: Why do some statistics remain stale despite a large number of row inserts?

During investigation of a slow query it appeared that the execution plan was exceptionally suboptimal (A nested loop performing 9 million executions of a seek where the estimated number of executions ...
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2answers
14k views

MySQL 5.1 InnoDB Configuration / 24GB RAM - bi-xeon high load

i'm running a facebook app which currently has 300 - 600 concurrent users (and growing). To get the hardware ready for growing i changed my i7 / 12gb ram / 2x 80gb intel x25 ssd's (debian 5.0 / mysql ...
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2answers
6k views

Updating 700 million rows to same value

I've got a data warehouse (oracle) where I need to set a column to the same value for all 700 million rows. I don't have admin access, or access to an admin, so this needs to be accomplished with ...
9
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2answers
255 views

Find rows where integer sequence contains a given subsequence

Problem Note: I refer to the mathematical sequences, not the sequences mechanism of PostgreSQL. I have a table representing sequences of integers. The definition are: CREATE TABLE sequences ( id ...
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2answers
13k views

Slow Performance Inserting Few Rows Into Huge Table

We have a process that takes data from stores and updates a company-wide inventory table. This table has rows for every store by date and by item. At customers with many stores, this table can get ...
8
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3answers
3k views

SQL Database Structure for RESTful API

I am creating a RESTful API. I am struggling to decide on the best way to design my database tables around my resources. Initially, I though a table per resource would be a good way to go, but I'm ...
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4answers
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Good, Bad or Indifferent: WHERE 1=1

Given this question on reddit, I cleaned up the query to point out where the issue was in the query. I use comma first and WHERE 1=1 to make modifying queries easier, so my queries generally end up ...
8
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3answers
992 views

Worse performance on a new server

We've been on a dedicated server (single quad-core, 6 GB RAM) and are moving to a new dedicated server (2x hex-core, 32 GB RAM). Both are Windows Server 2008, SQL Server 2008. The performance on the ...
8
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3answers
800 views

Create function in central database or repeat in each database?

One of my developers has written a SQL function that works like the VB.Net function (LastIndexOf) and wants to publish it. My question is what would be the reason to put this in a central database ...
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3answers
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SQL Server - Multiple running totals

I've got a base table with transactions and I need to create a table with running totals. I need them to be per account and and also have a few running totals for each account (depending on the ...
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InnoDB import performance

I'm struggling with bulk importing a quite big InnoDB-Table consisting of roughly 10 Million rows (or 7GB) (which for me is the biggest table I've worked with so far). I did some research how to ...
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2answers
856 views

Index fragmentation and SSD disks

I'm new to performance problems, but I saw some discussion that SSD disks solve performance problems caused by index fragmentation. Has anyone experienced this? I'm thinking of changing my hardware ...
8
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5answers
9k views

Does SQL profiler affect server performance?

I am facing a problem where the sql server 2008 fails for some high load. I need to find that load case and need to optimize the code so that it can handle the load. I have found on the internet that ...