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
89 views

Meaning of SQLIO output “counts per second”

I realise that my question isn't strictly 'database' but I know that a lot of DBA's will use the SQLIO tool to check I/O performance on their systems so I'm hoping that somebody here will be able to ...
2
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1answer
212 views

SQL Server full safety mirror commit overhead less then Time to send?

How is it possible that the time to send value is greater then the mirror commit overhead? The mirror operates under full safety so this means that the commit is only done @ principal when the commit ...
2
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1answer
68 views

Debugging SSAS Timeouts

I have a drill-through problem apparently related to security. Users in one role are seeing timeout failures when trying to invoke a drill-through action. They have permission on the action through ...
2
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1answer
319 views

How to ensure that date-range queries involving multiple time zones are sargable

I am building a web analytics application for search engine traffic only. You can see some screenshots here: http://myhappyanalytics.com/ It works similar to Google Analytics but it only saves and ...
2
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2answers
2k views

Cannot Utilize Maximum CPU and Memory Usage for MySQL

Good day. I know this may be a duplicate of other questions however I have applied all the suggestions in many of the threads, but I remain with the same problem. I have a single stored procedure ...
2
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1answer
964 views

Innodb Slow queries since convert from MyISAM

a few days ago we converted some write intensive tables from MyISAM to InnoDB hoping to have a better performance due the better locking system of InnoDB, but instead of gain performance, we start to ...
2
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1answer
2k views

Why does that query cause lock wait timeouts?

From time to time, I find a lot of these errors in my PHP error log: MYSQL.1213: Deadlock found when trying to get lock; try restarting transactionSQL The problem persists for about 2 or 3 minutes. ...
2
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1answer
226 views

How much overhead is involved with querying a DB on the same server?

History The company I work for had two databases, DB A and DB B, on two different servers. A contains information pulled from a COTS application database in addition to information from our own ...
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1answer
7k views

Mysql slowly uses memory until it starts to use swap

I am running a 1gb of RAM rackspace database server. For some reason in about 2 days the memory usage goes from using very little swap, to using 100mb. If I don't restart sql it will keep using more ...
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2answers
295 views

Localhost vs LAN Database Performance [closed]

Normally, what some of us do is to just host the database and web-server inside 1 machine. Meanwhile we also may focus a machine with high RAM just for the remote database on LAN and another machine ...
2
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1answer
197 views

Improve the performance and stability of a MySQL server

We provide a B2B solution, which is doing quite a lot of UPDATE, INSERT an DELETE operations. Our infrastructure at the moment looks like this: Home-Server ( MySQL (INNODB) + website ) 5 worker ...
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3answers
3k views

Mysql innoDB write operations are extremely slow

I'm having serious performance problems with MySQL and the InnoDB engine. Even the simplest table makes writing operations (creating the table, inserting, updating and deleting) horribly slow, as you ...
2
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1answer
110 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=# ...
2
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1answer
92 views

Help with database design

I'm quite the beginner when it comes to databases, so please bear that in mind. I need to store user statistics in several categories for an application. In the near future I will most likely need ...
2
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1answer
1k views

How to monitor INSERT failures?

An application INSERTS a parent record then child objects. Both these procedure call different stored procedures. Parent can have many child objects. Typically both parent and child would be inserted ...
2
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2answers
170 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 ...
2
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1answer
486 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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1answer
68 views

MySQL query took 98 seconds to run but EXPLAIN looks okay

I have a query that took 98 seconds to execute this morning, but I can't recreate the problem now, and the EXPLAIN output isn't giving me any clues. Am I missing something? Here's the SQL: SELECT ...
2
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2answers
201 views

MySQL : UNION script help

I have two tables which have roughly the same data but we could not mix them together due to the nature of the data input and presentation and to keep the table size small. We run the followign ...
2
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1answer
144 views

Optimising a query using hint locks

I have a stored procedure that is being called very frequently. For some database servers it is as often as 20 times per second. Unfortunately because different clients call this procedure, I can't ...
2
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1answer
87 views

MySQL Unions/Subselects not utilizing keys from associated tables

I've noticed by doing EXPLAINs that when a MySQL union between two tables is used, mysql creates a temporary table, but the temp table does not use keys, so queries are slowed considerably. Here is ...
2
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1answer
649 views

Poor MySQL for Drupal on Shared Hosting

My Drupal site is on a shared host where I cannot modify the my.cnf configurations but the database seems to be performing poorly. Here are some of the flagged issues that I can see... In ...
2
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1answer
137 views

Group_by and having vs Joins when table is self joined 5-6 times

Now the situation due to which this question came to me. Schema is Table User_Read_Book user_id | book_id Now I want to get users who have read certain books. Say give me users who ...
2
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1answer
948 views

Are many NULL columns harmful in mysql InnoDB?

As I explored the clustered B-tree index system of InnoDB, I think that the presence of many NULL (or small) columns has no significant effect on InnoDB performance. Does the presence of excess ...
2
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1answer
267 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 ...
2
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1answer
69 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 ...
2
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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. ...
2
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1answer
514 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; ...
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2answers
2k 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), ...
2
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2answers
909 views

Tuning SQL Server Performance

While profiling my application against SQL Server 2008 running against a JDBC Application most of the time consumed were by following COMMIT TRAN FETCH API_CURSOR & exec sp_cursorfetch I ...
2
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3answers
886 views

Loading a FACT table per day

I have a database with 13 billion rows, per day I have around 20-30 mio rows. On top of this I have one cube, one of its dimensions is DateTime that goes down to milliseconds. To load the fact table I ...
2
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1answer
444 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)?
2
votes
1answer
645 views

Unicode support of PostgreSQL and its performance

How is the Unicode support of PostgreSQL? If I want to save Unicode data does it have to go through the conversion process while storing and retrieving? If yes then what is the performance of such ...
2
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2answers
483 views

Clustered monotonically increased index insert performance

I have a table with field Id (bigint, IDENTITY) as primary key and clustered index on it. I inserted 400 rows and saw execution plan. I got: the relative query cost for this insertion 36% and for this ...
2
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3answers
583 views

Best database choice for a highly scalable web ticketing system?

Essentially, we are developing using Ruby on Rails and want to make a highly scalable ticketing system. Essentially we will have a small database (containing event details and tickets sold) that will ...
2
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2answers
961 views

Is it better to store calculated values or recalculate them on request? [duplicate]

Possible Duplicate: Storing vs calculating aggregate values At an old job, we had this database, it wasn't normalized rigth, some tables wheren't used anymore, it was patch after patch. In ...
2
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1answer
68 views

If an INNER JOIN in a query returns no rows, do additional INNER JOINS add a significant performance overhead?

If I make a query as follows: SELECT * FROM TableA A INNER JOIN TableB B ON A.AID = B.AID INNER JOIN TableC C ON B.BID = C.BID Does the INNER JOIN with TableC add significantly to the performance ...
2
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2answers
69 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 ...
2
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1answer
15 views

Is 'internallength' always useful in custom type definition in Postgres?

In our database we use a custom type to store 3D locations: CREATE TYPE float3d AS ( x real, y real, z real); In many examples I see INTERNALLENGTH used as a parameter with the definition of ...
2
votes
1answer
31 views

What is FT BATCH CMPLETE in the cmd column for sysprocesses?

I was trying to figure out what was causing high cpu usage in our sql server and found two processes that were consuming high CPU. When I queried sysprocesses to see what the spid was doing, it had ...
2
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2answers
53 views

How do dirty reads at both the transaction and table level provide increased performance?

I ran the following code past our architect as I thought there may have been a tautology between the isolation level and table hint: SET NOCOUNT ON SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ...
2
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1answer
77 views

Character varying index overhead & length limit

I have a unique constraint on a character varying column that will mostly have lengths of approximately 600 but could get to 10 million. I have read about B-Trees, but I can't determine how much disk ...
2
votes
1answer
56 views

File database vs application server database for concurrent performance & bulk data

I asked a question about Ripple's database implementation, and received this response: The ripple server uses SQLite for structured data and a configurable "back end" for unstructured "bulk" ...
2
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2answers
99 views

DBCC CheckDB causing high values for resource_semaphore wait type

On one of our production server, where SQL Server 2008R2 (Service Pack 2) is installed with 24 GB memory and 24 CPU cores grouped into two NUMA nodes, we are facing high counts for resource_semaphore ...
2
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1answer
89 views

Do triggers affect DB performance

I have a database with 250 small and medium sized tables. These tables are related with both MyISAM and InnoDB storage engines. There are multiple triggers that have been created on different tables. ...
2
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1answer
48 views

How to efficiently count rows in a query by limiting the number or found rows?

I have a website where I output a pagination with a limited number of pages, let's set it to 50 for example. That is, if there are actually 51 or more pages of content the 50th will be the latest that ...
2
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3answers
107 views

Will MySQL be effective when selecting a row from a table with billions of records? [duplicate]

Note: this is a hypothetical scenario Lets say that: I'm running MySQL, InnoDB engine, UTF-8 encoding I have a table with 50+ billions of rows The tables primary key is a BIGINT The table also has ...
2
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1answer
321 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. ...
2
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1answer
102 views

Does Windows Server File Compression slow Oracle DB performance?

I'm starting a new a new contract and I get to troubleshoot their Oracle instance... I'm more apps and sql, but I'll be trying to figure out their crashes and slow performance. Go figure. I can ...
2
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1answer
69 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. ...