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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276 views

Why are my queries getting really slow?

I own a WordPress installation, and Updated to 3.4.1. After the upgrade, I experienced a very strange slow-down. After all, I used the define('SAVEQUERIES', true); in my wp-config.php with ...
3
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1answer
1k views

Need advice for a 'tag' table design

My website has different content types. All content types should be tag-able (except if specified in the model, whatever). I can think of 2 options for my design: 2 tables option : 1 table for the ...
3
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2answers
538 views

Performance differences between executing via Linked Server vs. SSMS

We've had an issue reported where a stored procedure was behaving badly when called from some .Net code. On the face of it, that sounds similar to this case, which turned out to be due to EDMX, but in ...
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1answer
1k views

Can you have a WHERE clause with a greater than operator on a composite key?

I'm a web developer (not DB admin!) having performance problems processing a 1.7m record table on MySQL. Here is that table : CREATE TABLE `bbcmapimp_pc_raw` ( `postcode` char(8) NOT NULL, ...
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1answer
7k views

Query performance with subquery and IN clause

I am trying to select a range of data for multiple devices (unique serial numbers) from a historical table and was wondering why there is such a big difference in time for the following queries: ...
3
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1answer
591 views

Sql Server Performance Degradation in moving from 2005 to 2008

I have sql server 2005 setup for my performance bench marking exercise and I have put same database on another server which has sql server 2008 and exact replica in terms of hardware configuration. ...
3
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1answer
125 views

Database performance for determining entities assigned to users

I am interested in insight in improving performance in the following instance: I am currently working on an application that has a hierarchical entity structure where, depending on a user’s level ...
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1answer
1k views

Replication slows down on massive deletes

First of all, I'm not a DBA, but I'd like to get advice how to deal with the following issue. We have few database servers based on SQL Server 2008 R2 SP1. They have been organized as shown below, so ...
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2answers
174 views

How can a key lookup with zero executions and zero actual rows take time?

I have a query that is taking about 10 seconds to run and I am trying to optimize it. All the time is spent in the key lookup which is fine however in this case if I mouse over the key lookup in the ...
3
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1answer
109 views

Are there significant performance differences when linking to a simple data view, rather than a data table, in a simple data view?

Sorry for the long question, but let me give you my scenario. I have a DB that houses data exported from another DB. The containing tables are copies from the other (non-SQL) database. Each column ...
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1answer
4k views

sqloledb vs sqlncli - Performance difference or just feature set?

I've been running through some Classic ASP code recently and was wondering if there was a performance difference between connecting using: ...
3
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2answers
316 views

Comparing two XML query plans

Hopefully a simple one, if I have two (fairly complex, 30-40 node) .sqlplan files (from the same SQL text) what is a good way to compare them side by side? Or just have it tell me what it did ...
3
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1answer
93 views

Select performance problems with conditional index vs non-conditional on large volume table

We are trying to change some indexes on a large-volume table to be conditional indexes (function-based indexes) to reduce how much space is being used for indexes against this table. When testing the ...
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1answer
185 views

Excessive CPU use in vendor SQL Server DB

Background: I've got a SQL Server 2012 DB provided by a vendor so modification of queries and tables is limited. We do own the DB though, so we can add and maintain indexes. Indexes haven't been ...
3
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1answer
298 views

Is a clustered index on a child table in a parent/child relationship the most optimal index?

A clustered index will sort row data in a table according to the ordering of the fields in the index. If so, why would you (or would you not) want to create a clustered index on the child table in a ...
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1answer
265 views

Help with indexing narrow table with many millions of rows

I have a good amount of experience with SQL Server, but not much with indexes and I fear I'm a little bit out of my depth in trying to figure out how to correctly structure a table that has 100+ ...
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2answers
156 views

Do MySQL optimizations hold for MariaDB also?

I am a developer who will be starting a new project soon in which database performance will be crucial. The current candidate for the backend is MariaDB. I have worked with MySQL and MariaDB before in ...
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3answers
2k views

SQL Server 2012 performance degradation

We are running SQL Server 2012 SP1 on Windows Server 2012. The issue we have is that after some time the server automatically reboots. Checking the logs did not show any errors. When looking into ...
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3answers
2k views

MySQL query extremely slow after server restart

I am managing a very large database for a custom application I wrote to keep track of visitors. The DB server was rebooted for the first time in over a year - not even to install any updates, but ...
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1answer
274 views

How can I compare the server impact of transaction replication

We are developing a system that must extract data from an existing SQL Server 2008 R2 cluster. One of our design goals is to limit the performance impact on that cluster as much as is practical. ...
3
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1answer
122 views

Restoring with replace going incredibly quickly [duplicate]

So I have a database (on a SQL Server 2008 R2 SP2 instance) that is 2TB uncompressed, with a .bak file that is 500GB compressed. As I have been toying with the fastest way to restore this database ...
3
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1answer
296 views

What is Required to use Oracle Performance Manager to monitor SQL Server?

I am working with a customer who has several SQL Server and Oracle DBMS server instances. My customer would like to setup up performance data collection, monitoring and alerting for all of their ...
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2answers
3k views

SQL Query too slow on SUM function

I've a table with around 32 million rows having clustered unique index on CountryID,RetailerID,ProductID,DateID,EventID,TypeID and query is SELECT f.RetailerID , TypeID ...
3
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1answer
556 views

Group By primary key or DISTINCT increase query time over 1000x with limit

Also see http://stackoverflow.com/questions/17741167/hibernate-jpa-improve-performance-of-distinct-query but I realized this is mainly a PostgreSQL issue. My application uses a 3rd party extension to ...
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2answers
531 views

How to implement posts with “seen by” like facebook?

Inside a Facebook group there is a feature when every time see the group newsfeed it mark all posts as seen by me. And if I see a specific post inside a group thought a url ...
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2answers
7k views

Oracle insert through dblink performance issue

I'm trying to do an insert as select to a table via dblink. The query looks like this: Insert into MARS_SUPERVISORS_PUB@EDHPUB select {...} from edhper a, edhper b where ...
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1answer
1k views

SQL Server Performance Counters Relating to Disk Access and Log Files That Appear Concerning

I want to validate the optimal performance of our SQL Server and in doing so, I have gone through all the performance counters listed at the following link and create a trace log to analyze the data. ...
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2answers
157 views

SQL server performance and tuning

I am working on a system, there is a cisco load balancer that can handle 40K requests. There are two app servers. There are 12 or so web services. and there is a SQL server with 2TB of data. ...
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1answer
448 views

Load Testing Crash Course

Can someone point me at a good resource to get a crash course in load testing. I have a sql server machine that I need to load test but I havent been thruogh the process before. Also we do not have ...
3
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1answer
27k views

What queries is Oracle executing, how frequently, and time-taken?

I have a (Java) web-application, that of course executes many queries (selects, inserts, updates, deletes) to the Oracle Database. I want to find out the following for last 7 days: SQLQuery ...
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1answer
777 views

Will one nvarchar column affect query performance?

I have one column that I recently converted to nvarchar(100) to store Asian characters. The other columns in this table, and the other tables in the same database, use varchar, int, bit and datetime. ...
3
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1answer
144 views

Does updating a partially indexed field add or remove it from an index in Postgres

We can create a partial index for a field in Postgres. I am looking at using this to stop rows which are archived from being in an index on a created_at field: First we create the index: test=# ...
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3answers
669 views

Why does the query cost change so much and how to prevent it

The query causing me the issue is too big, but the piece that seems to be the core is quite simple, I will try to go with that: The query has an structure like: SELECT ... a lot of stuff ... ...
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2answers
248 views

Which performance can I expect?

I'm running a Postgres 9.1 database on a Debian Squeeze server. It's a paravirtualized XEN guest system with 4G RAM and 1 CPU core, based on a i7-2600 host system with Linux software-RAID1. I'm ...
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2answers
3k views

How to setup mysql on tmpfs?

How to setup mysql on tmpfs ? I am reading a tutorial in french, where the author do it this way : 1.) Create a tmpfs directory : mkdir /var/tmpfs mount -t tmpfs -o size=1G tmpfs /var/tmpfs chown ...
3
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1answer
4k views

mysql: deleted performance_schema, is it a problem?

Been following this tutorial http://stackoverflow.com/questions/3927690/howto-clean-a-mysql-innodb-storage-engine/4056261#comment14041132_4056261 in the process I deleted performance_schema along ...
3
votes
1answer
793 views

Will an index that is a partial key of the begining of another index perform any better than the longer index?

If I create an index that is a partial key of the begining of a second index, will SQL Server get any significant gains retreiving the results from the simpler index, when the search criteria matches ...
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1answer
527 views

Fastest key-value store for random disk reads?

I want a key-value store, with records stored on disk. (There are too many for memory.) I want to use a single machine. What key-value store will provide the fastest random reads (off disk)?
3
votes
1answer
127 views

ASP.NET & SQL Server 2012 timeouts once a month

We have an intranet site which works fine, except one day a month. There are slow queries, unoptimized tables, tables with ~8 million records, etc. but daily usage is fine, although some ...
3
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1answer
322 views

Pagination performance, with subquery, inner join and where

I am trying to optimize following query (this is most simplified version I could came up with): SELECT tr.Id, StatusDate FROM ( SELECT tr.Id, tr.StatusDate FROM mon.ArchivedTaskResults_201504 ...
3
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1answer
44 views

io_stall question

I just installed SQL Server on new hardware and ran a test script to show io_stall information by file. Nothing else has been loaded yet, just a fresh install of SQL Server 2012. Why are the ...
3
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1answer
366 views

Prepared statement overhead

I am using libpqxx to communicate with a PostgreSQL 9.3 server. For multiple table inserts, if they are split into individual prepared statements, they cost approximately 2ms each. If they are all ...
3
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1answer
683 views

PostgreSQL 9.4 analysis, performance of normal column, indexed column and jsonb key

If I have a table containing: CREATE TABLE test( id SERIAL PRIMARY KEY, name VARCHAR(200), age INT, data JSONB ); and data column populated with {"name": xxx, "age": yyy}, sometimes ...
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1answer
140 views

Why does my query end up with two seeks instead of one and how do I fix that?

I have these two tables: CREATE TABLE [TaskItems] ( [ItemId] UNIQUEIDENTIFIER NOT NULL UNIQUE PRIMARY KEY, [LastOperationTime] DATETIME NULL DEFAULT GETUTCDATE(), [OwnerId] ...
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1answer
247 views

Handling a chat room in a database

I have been searching all day to find a better answer to my question but those I found was useful but do not critically analyse my question. I am building a chat room using php, mysql, jquery and ...
3
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1answer
1k views

Debugging why postgres is snowballing with system cpu usage

I am having an issue where my postgres database which run on a dedicated machine is getting hammered with kernal level cpu usage. This essentially takes down the web service that run on this database. ...
3
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1answer
3k views

Table-valued function runs fast, but slow from another function [closed]

Disclaimer: I'm a senior sysadmin who's trying to help our development team speed up the production database. Our users are hurting, bad. Please don't shoot me for not being great with SQL The ...
3
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1answer
498 views

MySQL / Fusion IO Configuration Question

I need a little configuration optimization. I think what I have is pretty good but feel like there's still room for improvement. Current Config [mysqld] user=mysql datadir=/var/lib/mysql ...
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1answer
310 views

Forwarded Records, effective way to fix them

I'm dealing with an issue in SQL Server databases of an application. This application is used for Healthcare and I only maintain the databases, I do not create the application. Clients are facing the ...
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1answer
659 views

Insert performance with Geography column

I've been tasked with inserting data into a SQL Server table with a geography column. I've found that my times for doing inserts (same data 1.5 million rows) go up increasingly. I started out with no ...