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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1answer
440 views

Getting ratio of reads to writes on SQL Server

Sorry I am not a DBA so bear with me. I wanted to get a better understanding of the ratio of reads to writes in our archiecture. The best to get this is at the database. We are using SQL Server ...
2
votes
1answer
295 views

optimal table design mysql with primay key and varchar value

I have a table: id (PRIMARY KEY AUTO_INCREMENT) value (UNIQUE KEY) which currently holds over 50 millions rows (and growing fast) and is hit hard: process 1 queries this table (>200/sec) with a ...
4
votes
1answer
1k views

PostgreSQL versus MySQL for EAV structures storage

Is there any practical difference or what are the advantages of using Postgres 9.x versus MySQL 5.x for storing EAV (Entity-Attribute-Value) structures, especially in terms of read performance?
5
votes
3answers
545 views

Just how much is a query supposed to slow down the whole system?

This is similar to my earlier question but more generic. I have a system with 16GB of memory, 16 cores, supposedly quality hard drives, RHEL 5, MySQL 5.0.x. Yes, I know, we're working on upgrading ...
3
votes
1answer
575 views

PostgreSQL WAL Archiving: Does having archive_mode set to 'on' without copying logs cause performance issues?

Using PostgreSQL 8.4/CentOS 6: if I set the archive_mode parameter to on in postgresql.conf, but don't actually store the generated WAL files anywhere via the archive_command parameter, is there any ...
2
votes
1answer
72 views

Single field instead of several fields

There is a relational database with the following Users table User Id Name Age Parents Friends Colleagues ... And there are tables Parents, Friends, Colleauges, etc. Due to specifics of database ...
4
votes
2answers
5k views

Performance settings for MyISAM tables - keep everything in memory

I have a 8-core MySQL server with 32 GB of RAM, holding 40 MyISAM tables (total: ~4GB of data). Since the databases size is several times smaller than the available memory, how can I make full usage ...
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vote
3answers
133 views

Keeping an eye on contention

In SQL Server, I am using the following command to see blocked sessions: select * from sys.sysprocesses where blocked>0 This is super. The problem is I need to see what block sessions there ...
1
vote
1answer
261 views

MySQL replication risks for the master

I have a production MySQL server, fairly heavily loaded with an INSERT-only load on one of its databases. I'd like to attach a non-production (sitting on my desk, more or less) replication slave to ...
2
votes
1answer
341 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 ...
5
votes
3answers
610 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 ...
4
votes
2answers
476 views

Huge database logging of event type rows and ways to optimize it

We have a database that stores events. Events are generated at a 1000 per sec rate. We need to keep these events accessible for some years. Usual use of these events is selecting some of them from the ...
4
votes
2answers
798 views

Performance degradation after rebuilding indexes

I am optimizing some server application task that uses database (querying, complex calculations, data insertions...). Execution of this task spends about 16 minutes (I have tested it 3 more times) and ...
5
votes
2answers
575 views

Large accounting table, best way to partitioning by two dates

I need to create a log table to stores the connections to out network (last 3 years, after that the log will go into backup). The hardware/software used is proprietary, and for accounting it just call ...
3
votes
2answers
843 views

How to backup a MySQL database without slowing the application?

I'm an application developer and wondering about our database backup strategy. Right now our sysadmins backup our database every 8 hours. I don't really know how the do it, but while the backup is ...
2
votes
1answer
46 views

What will happen when a forum uses 24 char length as an URL ID?

I found a forum using self made/custom engine still in beta version, previously using vBulletin. Now, their new engine uses very long URL id, 24 char length. ...
4
votes
1answer
733 views

Design the big data with mongo db

I'm working now on the implementation of the following feature: Say I have a collection in mongodb with millions of entries (very big say 100M), each entry is of type {"uniqId", "properties"} for ...
1
vote
1answer
713 views

Usefulness of Foreign Key WITHOUT reference option

Sorry, if this is naive question, but I searched a lot and did not get a vivid answers. Consider a simple InnoDB FOREIGN KEY without ON DELETE or ON UPDATE I think this will avoid INSERT of a value ...
2
votes
1answer
704 views

PostgreSQL partitioning query performance inexplicably bad

I find this a bit mysterious. The cost of getting the maximum value out of just the partition parent table (which is empty) is very cheap: evlampts=# explain select max(timestamp) from only mcdata; ...
4
votes
2answers
2k views

Is there a MySQL maximum database or table count?

I am in the process of creating a massive archive of bitboards stored in MySQL. In my schema, there are four linked sets of bitboards which--for query sake--are represented in four different tables. ...
5
votes
2answers
2k views

Speed up INSERTs

I need to have a way to insert to a table, fast, synchronous, with minimal duration. What I've tried ("blind") is : Have no index on the table whatsoever Switch to simple logging (from full logging) ...
2
votes
2answers
298 views

Does the number of indexes effect the modification of table?

First of all Good morning ! Today I got one question regarding indexes and tables. Actually I am not facing problem regarding this but due to curiosity I want to post !! Now come to the point, ...
1
vote
1answer
224 views

Slow enumeration of schemas and tables in a largish database

We have a Postgresql 8.4.8 database server on a Debian system with a database that has 500+ schemas with roughly 300+ tables each. The schemas and tables are created by scripts, we cannot influence ...
9
votes
3answers
4k 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 ...
0
votes
0answers
31 views

Fix missing performance counters [duplicate]

Possible Duplicate: How to revive SQL Server 2008R2 performance counters? On one machine, I have an instance of SQL Server 2008R2 Enterprise, Visual Studio 2010 and VS 11 Developer Preview. ...
4
votes
1answer
2k views

Performance difference between SQL Server Linked Server and direct query

A Management Studio query pane connected directly to a remote sql server executes and displays a simple table query of (SELECT * FROM table) in just under 2 seconds. The same Management Studio but ...
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vote
2answers
860 views

Very slow performance from MySQL

I have the following procedure: drop procedure if exists deletebatches; create procedure deletebatches() BEGIN declare acount int default 0; declare done INT default 0; declare abatchno ...
2
votes
1answer
868 views

tempdb on raid1 isolated or raid10 shared with high write db

PROPOSAL 2 8x600gb raid 10 mdf array 4x600gb raid 10 ldf array PROPOSAL 3 8x600gb raid 10 mdf array 2x600gb raid 1 ldf array 2x600gb raid 1 tempdb mdf/ldf array READ/WRITE STATS ON ...
18
votes
5answers
6k views

SQL: What is slowing down INSERTs if not CPU or IO?

We have a database for a product that is write-heavy. We just bought a new server machine with a SSD to help. To our surprise, the insertions were not faster than on our old machine with much slower ...
10
votes
2answers
5k views

INSERT performance difference between temporary tables and table variable

I have the following issue in SQL Server 2005: trying to inserts some rows into a table variable takes a lot of time compared to the same insert using a temporary table. This is the code to insert ...
2
votes
2answers
3k views

Oracle aggregate function performance

Can Oracle be smart about aggregate functions, such as MIN(), MAX(), and (AVG)? My testing shows that it seems to be surprisingly stupid. I have the following query: SELECT COUNT(userId), AVG(age), ...
4
votes
1answer
488 views

SQL Express 2008 R2 on Amazon EC2 instance: tons of free memory, poor performance

The old SQL Express 2005 was running on a low-end single Xeon CPU Dell server, RAID 5 7200 disks, 2 GB RAM (SBS 2003). I have not done any baseline measurements on the old physical server, but the ...
10
votes
2answers
2k 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 ...
2
votes
0answers
82 views

Permon counters on SQL 2005 mirroring (user defined counter log file is empty) [closed]

I've been attempting to gather performance counters for mirroring using perfmon, over a period of time and saving this to a log file. I am able to do this without problem for general SQL Server ...
4
votes
2answers
4k views

oracle distinct doing sort

I'm getting poor performance from DISTINCT. The explain plan indicates that it is doing SORT (GROUP BY) which doesn't sound right. I would expect some kind of HASH aggregation to produce much better ...
3
votes
2answers
436 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 ...
6
votes
1answer
192 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 ...
4
votes
1answer
861 views

Ways to speed up IN queries under PostgreSQL

I have a query of the following form: SELECT * FROM twitter_personas WHERE twitter_user_id IN ($1, $2, $3, ..., $25000) The IN query has anywhere from 10 to 25000 values. The query runs for minutes ...
5
votes
2answers
604 views

Unexpected extremely long query time (~5 minutes using nested WHEN-INs)

For the first time, I am running up against a horrifically long execution time of a MySQL query (~5 minutes). The data in the database is highly (and not arbitrarily) normalized. It very efficient ...
8
votes
2answers
572 views

Pros and Cons of Checking if value exist for unique column or let db raise unique error on inserting

While writing a query other day a thought came to me and have stuck in my mind. What is preferable, first checking if a value for a unique column exists and then inserting or insert and let db raise ...
2
votes
2answers
358 views

How to quantify TEMPDB usage in relation to other databases hosted on same hardware?

Working on a project to decide if configuration 1 or 2 is the best way to organise disks for my SAN: Config1 (sql 2008): 8 disks @ raid 10 data 2 disks @ raid 1 logs 2 disks @ raid 1 tempdb 2 disks ...
2
votes
3answers
404 views

Express union which is dependent on other results

I would like to make a union of two tables that are actually in a hierarchical constellation. How would I write that in relational algebra? Say table A is the parent of B in a 1:n relationship. ...
2
votes
1answer
205 views

SQL from/where or join?

I was wondering performance wise what would be faster a join or a from and where query. I am trying merge and update query but performance is terrible?
2
votes
2answers
708 views

How to compare performances of two databases

There are two database servers and I want to compare their performances. Both have Windows operating system and and Oracle (10.2.0.4 and 11.0.2) database. Both are OLAP databases with 15-20 users ...
3
votes
2answers
2k views

How can I optimize performance on a MySQL ndbcluster?

So, this is what I have: A simple table classes__to_students: |class |student| --------------- Math Alice Math Bob Math Peter Math Anne Music Bob Music Chis Music ...
5
votes
2answers
2k views

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 ...
1
vote
1answer
65 views

Reading and writing the common data

I have a couple tables and application service that intensively inserts, updates its. From the other hand some client application have to read data using those tables. Sometimes client application ...
9
votes
2answers
573 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 ...
1
vote
2answers
1k views

How to keep one query from slowing down entire database?

Using MySQL 5.0.x, we have a process to generate benchmarks for our business that consolidates a bunch of data, then pull out data based on certain criteria. This process used to take 18 hours, it's ...
3
votes
1answer
4k views

I have lots of free memory. How do I use it to increase performance?

I am running Litespeed (with suExec, PHP SAPI), MySQL, DirectAdmin, named on a VPS with a 16-core Xeon CPU and 2GB RAM. Currently, only 300 MB out of 2048 are used. It might sound a stupid, but how ...