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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Why performance degradation with query hint FIRST_ROWS(1000)? [closed]

I have a query with user supplied arguments that can produce a very high amount of rows depending on the user's input. In case the user supplies very unselective arguments, the query takes a lot of ...
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2answers
1k views

Database locking issues?

I have run into a transaction related issue on a SQL Server 2008 production database. A brief overview is that we have a website that has numerous concurrent users around the state, who do GUI type ...
6
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1answer
1k views

MySQL table creation insanely slow

A simple table creation on one of my MySQL databases takes forever: mysql> CREATE TABLE blah (id BIGINT UNSIGNED NOT NULL PRIMARY KEY); Query OK, 0 rows affected (16.58 sec) The machine is quite ...
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2answers
1k views

How can I save a severely fragmented database/table?

I've recently made a discovery that might explain my slow SQL run times. I found out that the default in SSMS is to allow mdf growth of 1MB at a time. When the size of one table alone is roughly 23 ...
6
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1answer
477 views

Huge differences of performance of MySQL in two servers

We have a MySQL server installed in two different machines, a testing server and a production server, both windows, which is used by a web application. The problem is that there are HUGE performance ...
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2answers
626 views

Major Discrepancy Between SQLIO IOPS/Throughput Stats and DBCC CHECKDB Operations

I'm conducting time trials on a new SSD array running both SQLIO tests and a real-world workload of DB restores and DBCC CHECKDB calls. I'm seeing a major discrepancy between the IOPS and throughput ...
6
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2answers
455 views

MySQL: Does the order of the fields in a table make a difference in performance?

Specifically I am wondering if I should place all my fixed length fields like int, timestamp, char at the beginning of the CREATE TABLE and place all the variable length like varchar at the end. ...
6
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2answers
655 views

Transaction speed benchmarks for mySQL v5.6 replication - seems very slow

I'm trying to select the best configuration for our new infrastructure but got a bit confused about the results. I used sysbench v0.5 for the tests: prepare data sysbench ...
6
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1answer
780 views

Extremely Slow StatMan query issue with #SP2010 farm

The issue I’m experiencing is explained in a blog-post I created for this, (easy to refer to and to manage the responses / solutions in 1 location) which can be found here: ...
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2answers
4k views

When to make changes to the cost threshold for parallelism

While examining a performance issue , I have seen an influx on CXPACKETS suggesting I might need to look at the cost threshold for parallelism and perhaps the MAXDOP. Before making any drastic ...
6
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1answer
356 views

Sudden increase in log_file_sync waits

I'm on Oracle 11gR2 with a 2 node RAC system. It's shared fiber storage to an EMC Clariion. Last friday things went bad..fast. All of the sudden processes that normally ran fine for years became ...
6
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1answer
180 views

Start/Stop MySQL

I'm seeking help to understand what happens when the following command line is executed: root@prodn$ service mysqld stop Yes, it shuts down the MySQL server so access to it is no longer available ...
6
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1answer
316 views

Landed as BI, but databases are a big WTF, what to do?

Maybe a duplicate, but I believe my case is a bit different. From one of the answers I got to this post on SQL Server Central that also comes handy too but is not quite the same scenario: 9 Things to ...
6
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1answer
162 views

What is a good way to determine the performance I should expect from a PostgreSQL server?

Trying to figure out how I should expect my database to perform. Basically, I need to determine when the server I have set up is reaching its performance limits - which would help me plan server ...
6
votes
1answer
449 views

Backup to three drives suddenly slow

The situation: I have a 1.3 TB Database (SQL 2005) that I am currently backing up to 2 network shares on separate machines and on one local USB. (Don't ask why - long story involving a DBA that quit ...
6
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3answers
603 views

Single query sending and retreiving duplicate data on MS SQL Server?

Very odd thing happening. It would appear that all queries against a particular database in our system are periodically "running slow". Ie "normal speed" for 5 minutes then slow for 5 minutes ...
6
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1answer
517 views

Using an RDBMS for querying tens of Terabytes of time-series data?

I stumbled over an algorithmic / data-structures question over on SO, which I'll short quote: (...) opinions regarding best of breed data structures to be used for indexing time-series (aka ...
6
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1answer
197 views

What is the expected performance impact when dropping a large table

I have a 100G+ innodb table that needs to be dropped in a production environment. I am trying to do this without interruption to service. The table is no longer being written to, and needs to be ...
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3answers
384 views

Reducing the size of a database

SQL Server newbie here. I'm a MySQL guy. I'm having a look at something for a client in their 2008 SQL Server, and need some advice. Whoever designed the database chose to log insane amounts of stuff ...
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3answers
313 views

SQL Server clustered index, index balancing and insert performance using NewID

I have a large (6db) trace table. It has a clustered key (DateTime) which is created through GETDATE(). The connection pool for connections to this database/table rises as high as 50 on average ...
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5answers
4k views

Improve sort performance in PostgreSQL?

I've got a simple blog database in postgres-8.4 which has two tables, articles and comments. I have a query (generated by Django) that wants to get the latest article of type 'NEWS' and also find the ...
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2answers
2k views

Compare Microsoft SQL server performance between virtual and dedicated server

I have a dedicated windows 2008 r2 server at the moment and I am thinking about migrating to a virtual server because of the costs. Now I know that SQL should be on a dedicated server, but the ...
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2answers
387 views

How to design index for faster deletes

I want to speed up following piece of code delete from ssn_sdo where (art_id=@art_id and skl_id=@skl_id and @level=0 ) or (art_id=@art_id and skl_id=@skl_id and @level=1 and ...
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3answers
6k views

How can I configure MySQL Innodb to handle 1000s of inserts per hour?

I have a very high traffic website where it is possible that 1000s of new records are inserted every hour. This one error is crippling the site: PDOException: SQLSTATE[40001]: Serialization failure: ...
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3answers
622 views

SQL Server 2005 uses 1GB of RAM

Is this normal? To be exact it uses 1,068,000 KB. It occasionally shoots up to 1,400,000 if query takes too long. My total system memory is 3GB and I am running WinXP. Is there a specific amount of ...
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3answers
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Is the ADO.NET Entity Framework known for generating poorly performing queries?

This question is inspired by the comment posted to the latest ServerFault blog post: Are you guys still using LINQ to SQL? I know I can use SQL Server Profiler and/or the ToTraceString method to ...
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3answers
128 views

Dynamic temporary index creation

In my undergrad databases course, my professor mentioned that some DBMS software is so advanced that it can detect when a long-running query would benefit from an index. The DBMS can then create that ...
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3answers
10k views

Optimizing InnoDB default settings

I looked into my.ini and saw various default settings. My database is running on a single stand-alone PC. I want to optimize the performance of InnoDB and MySQL in general for performance. There is no ...
5
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3answers
459 views

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 ...
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3answers
3k views

Is MariaDB a suitable drop in replacement for MySQL on a standard LAMP stack?

I've been wondering lately what (if any) are the improvements available in MariaDB over 'conventional' MySQL? I understand that where platform interoperability and/or backwards compatibility may be ...
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5answers
4k 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 ...
5
votes
2answers
2k views

Index on primary key not used in simple join

I have the following table and index definitions: CREATE TABLE munkalap ( munkalap_id serial PRIMARY KEY, ... ); CREATE TABLE munkalap_lepes ( munkalap_lepes_id serial PRIMARY KEY, ...
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2answers
362 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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5answers
862 views

Advice with date column SQL Server 2005

I have two datetime columns in SQL Server 2005 that I need to query without the time portion of the datetime. Currently, my query looks something resembling this (just an example): WITH Dates AS ( ...
5
votes
1answer
761 views

Does MySQL still handle indexes in this way?

Dropping a duplicate index in MySQL was taking rather long, so while I was waiting I searched about it & found this post from 2006, talking about how MySQL handles ADD and DROP index. If a ...
5
votes
4answers
2k views

T-SQL INNER JOIN Optimisation

Well, I really have read so many articles, used different techniques and done some random things to do this. My problem was that a have big tables (over one million rows) and some small (with few ...
5
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2answers
137 views

Are existing entries immediately included into a newly created index?

Suppose I have a table Stuff with a column City and no indices including that column. I populate the table. Then I decide to create an index: CREATE INDEX [StuffOnCityIndex] ON [dbo].[Stuff](City ...
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3answers
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MySQL general query log performance effects

One of our customers who has a somewhat problematic web application would like us to log all the queries for a period of 24 hours. I wouldn't know how much data it will actually write. The amount ...
5
votes
3answers
5k views

Investigating high SQL waits, especically LCK_M_U

Recently I have been struggling with SQL server performance and although we have fixed a huge multitude of basic errors in the config it is still performing badly. To clarify it is not overall ...
5
votes
1answer
2k views

In a CASE Statement, which is faster: “WHEN [field] in (0)” or “WHEN [field] = 0”?

I'm looking at a stored proc that another guy has written and every WHEN clause is using an IN statement instead of =. My gut tells me this isn't as fast, efficient, etc. For example: CASE WHEN ...
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2answers
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The order of INNER JOIN's

I would like to know if there are any rules about the order of INNER JOIN's in T-SQL 2000. I had 62x the performance on my query when my INNER JOIN that act like a filter is placed at first instead ...
5
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3answers
238 views

When you select from a table on an indexed column and order by that column in the opposite direction of the index, does the index help

Let's say I have a large table of transactions with a date field and an index on that field in ascending order. If I select that field from the table and order by in reverse order is it able to ...
5
votes
1answer
747 views

Optimum configuration for 4 SSD drives

I would like to move a SQL Server database from a shared configuration with the web-server to it's own dedicated box. My current budget will allow me to put 4 disks together in an array with a single ...
5
votes
1answer
3k views

Qcache_free_memory not full yet I get alot of Qcache_lowmem_prunes

I just started dabbling with the query cache for our CMS. Can anyone tell me (or at least give a good guess) why I get a lot of Qcache_lowmem_prunes when more than half of Qcache_free_memory is free? ...
5
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3answers
292 views

SQL Server how to test filegroup IO

We have a customer who is switching from SAN storage to directly attached storage. Our SQL Server database has several filegroups all of which has been deployed on the same LUN. In order to determine ...
5
votes
2answers
698 views

SQL Server performing slow

I have a Microsoft SQL Server running on an IBM server with 10 cores and 64 GB RAM. I have from 100 to 300 users working concurrently on the server. Users complain about slowness of the application. ...
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2answers
1k views

Slow ORDER BY with LIMIT

I have this query: SELECT * FROM location WHERE to_tsvector('simple',unaccent2("city")) @@ to_tsquery('simple',unaccent2('wroclaw')) order by displaycount I'm happy with it: "Sort ...
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4answers
7k views

Optimising join on large table

I am trying to coax some more performance out of a query that is accessing a table with ~250-million records. From my reading of the actual (not estimated) execution plan, the first bottleneck is a ...
5
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1answer
182 views

Is my function nondeterministic one

I have two functions: fn_Without_Param and fn_With_Param CREATE FUNCTION [dbo].[fn_Without_Param] ( ) ... INNER JOIN .. ON .. AND SubmitDate = CONVERT( varchar(10), GETUTCDATE(), 101 ) and /* ...
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2answers
2k views

Does a TRIGGER improve the performance?

I understand that TRIGGERs are useful, as they take care of subsequent queries, but do they have an advantage from performance point of view too? Replacing two or three queries as INSERT INTO table1 ...