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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4
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3answers
11k views

Slow insert in SQL Server 2008

Our products' database contains an audit trail table: CREATE TABLE gn_AuditTable( gn_ObjectId int NULL, gn_Action smallint NULL, gn_Time datetime NULL, gn_UserId int NULL, gn_Login ...
2
votes
4answers
815 views

Advice on choosing a really fast DBMS

I am working on a project that does real-time monitoring of data being transmitted, and logs if there are any of the various type of errors, etc. The CRUD operations are real-time. We initially ...
5
votes
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 ...
2
votes
2answers
3k views

Will altering order of columns in GROUP BY affect performance?

I have a SQL query like this: SELECT A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END), COUNT(D) FROM SomeTable GROUP BY A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END) On a huge dataset the actual execution plan ...
2
votes
2answers
2k views

Improving performance of nasty nested-view joins

I have a moderate-sized database spread out over a few tables, the rough architecture is: Input Data (Data ID, Session ID and a few fields of statistical importance) Input File (Data ID and a blob) ...
5
votes
2answers
936 views

Teradata: How to design table to be normalized with many foreign key columns?

I am designing a table in Teradata with about 30 columns. These columns are going to need to store several time-interval-style values such as Daily, Monthly, Weekly, etc. It is bad design to store ...
3
votes
2answers
437 views

How do I count rows with two properties in one index scan in SQL?

I have a table Units where I have rows ItemId, ItemCreationDate, ItemUnitsCount. ItemId is a primary key and I have a clustered index over it. I need to output the following: for each day I need to ...
5
votes
2answers
4k views

Frequently slow queries while in the 'Update' state

I have two tables that I update very frequently, one with a direct UPDATE .. and another INSERT .. ON DUPLICATE KEY UPDATE ... Normally these queries are instant but at times will take 0.1s to 1+ ...
6
votes
3answers
617 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 ...
2
votes
2answers
1k views

Does it ever make sense to use RAM Disk to force RAM allocation for tempdb with SQL Server 2008

If I give all RAM to SQL Server, it will use it's own pattern to determine what RAM to allocate for what. If I allocate portion of RAM as RAM Disk and put tempdb into that disk it will force RAM ...
7
votes
2answers
1k views

Investigate peak in MySQL throughput

Recently one of our servers has ran out of memory and crashed. After reviewing the munin graphs, it appears that the only metric (other than memory usage) that peaked just before the crash was the ...
1
vote
1answer
326 views

What can cause an UPDATE statement to execute endless? [closed]

I have a stored-procedure which is executed at 7 o'clock in the morning that updates the database because new records were imported at night. Today it started but never endet. So i've tried to run ...
6
votes
1answer
338 views

Is there a quickish, straighforward way to measure Transactions Per Second on SQL Server 2000?

The sys.dm_os_performance_counters DMV introduced in SQL Server 2005 makes this task somewhat trivial. However, my Google-Fu has been blocked in finding a way to do this in SQL Server 2000. How can ...
1
vote
1answer
130 views

Sql Server Resource Governor - track IO

I know I can use the performance counters to track Resource Governor CPU and Memory Usage. Is it possibly to track the I/O usage for each work load group? I haven't seen anything specific or any ...
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, ...
6
votes
1answer
523 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 ...
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vote
2answers
1k views

Do I need SQL_NO_CACHE for write intensive query?

When I establish a connection to DB, I have to write about 30,000 records with an INSERT statement. I've read in a book that I should do it ! Questions Do I need to do SQL_NO_CACHE ? Is it gonna ...
5
votes
1answer
3k views

SELECT with large WHERE IN clause taking long time

I'm pretty new at all this so be gentle :). I have large medical DB where I need to extract data for patients based on selected doctor(s). Right now I build a patient list by SELECT patID FROM ...
2
votes
2answers
2k views

Will an ALTER TABLE ADD COLUMN on a slave break replication?

I need to add a last_modified column to a MyISAM table tbl_items. The crux of this problem is that tbl_items houses several gigabytes of data. Also of note, I am using a master-slave deployment with ...
4
votes
3answers
2k views

PostgreSQL - Help Optimizing SQL performance - full text search

I have a big table ~15M records called entities. I want to find top 5 entities matching "hockey" in their name. I have a Full text index built for that, which is used : ...
25
votes
1answer
4k views

USING construct in JOIN clause can introduce optimization barriers in certain cases?

It was brought to my attention that the USING construct (instead of ON) in the FROM clause of SELECT queries might introduce optimization barriers in certain cases. I mean this key word: SELECT * ...
4
votes
5answers
12k views

Mysql: Insert performance INNODB vs MYISAM

I am inserting into a simple small table with 5 attributes and 1000 rows. I observed when the engine is INNODB, each insert is taking 0.03 - 0.05 seconds. I changed the engine to MYISAM, then the ...
3
votes
2answers
308 views

Reinitializing Subscription Performance

I have 4 Servers, Servers A, B, C, D. Server A publishes a Replication instance, and Servers B, C, D have Pull Subscriptions to it. Server B's subscription needs to be Reinitialized, but I am ...
2
votes
2answers
2k views

How to sync two MySQL high load tables with 10M rows?

I have two identical MySQL innodb table with 10M rows each. One is used at backend while other at application end. Thus, either of them loaded. I need to synchronize them in a way which is fast and ...
0
votes
2answers
2k views

Disk performance causing SQL Server Command Timeout?

I setup a perfmon collector to capture data around some recent SQL Server command timeout errors and most indicators point to disk issues. CPU and memory numbers look normal. This is a SQL Server 2008 ...
9
votes
4answers
10k views

Why using innodb_file_per_table?

There are many articles exaggerating (IMHO of course) the need for innodb_file_per_table. I understand that with innodb_file_per_table, there should be a better control over the individual tables; ...
2
votes
2answers
1k views

Trying to optimize query for performance (MySQL)

So I have this table that has a lot of foreign keys but when I will a record, I need to join all on those tables because I generally need those fields for the record to make any sense. The basic ...
0
votes
1answer
911 views

slow index scan on postgresql 9.1

I have a view which is amazingly slow :) It joins two tables only, having a few simple WHERE conditions and one in a form of a subquery (see SubPlan1 below). The simplest condition is checked as an ...
3
votes
1answer
208 views

PostgreSQL synchronized commit performance

I'm setting up a pair of PostgreSQL servers. Because cash is short I can only afford one high class server and some crapy backup box. If the expensive high end box should catch fire, operations can ...
5
votes
2answers
3k views

Oracle's Merge v. Select->Update/Insert

What is the faster statement? A MERGE or Select->Update/Insert depending on if it returns a value? I'm trying to optimize a database, but I haven't found any speed tests comparing the two. I found ...
16
votes
5answers
5k views

Why are periodic restarts required to keep my instance performing well?

We've got a production DB server on SQL 2005. Everything runs normally for a while, but after a couple weeks we see a notable performance drop. Only restarting SQL Server brings performance back to ...
1
vote
3answers
485 views

Checking if the query is made async or sync on SQL Server 2008 R2

I have tried to make async calls to my SQL Server instance as you may see on my SO post: ASP.NET MVC 4 asyncronous database call: never returns the HTTP response I did a benchmarking and the sync ...
3
votes
3answers
471 views

SQL 2008 Developer Edition, not using all CPU´s

My SQL Server doesn´t want to use the second CPU for our Vault database. I tried to use different configurations for the CPU affinity in SQL Management Studio, but doesn't seem to fix it. I've read ...
11
votes
4answers
10k views

Mysql int vs varchar as primary key (InnoDB Storage Engine?

I am build a web application (project management system) and I have been wondering about this when it come to performance. I have an Issues table an inside it there are 12 foreign keys linking to ...
5
votes
2answers
207 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 ...
5
votes
1answer
5k views

mySQL query optimisation — multiple joins or select … where not in (select distinct…)?

Background I have a Drupal install accessing a large users database (~200k rows) and my "People finder" functionality needs to access all those rows (in a random order). I don't seem to be able to ...
2
votes
1answer
545 views

Maintenance Plan Takes Too Long - Locks Tables - Indexing To Blame

System: I have a Maintenance Plan that Rebuilds Indexes for Several Tables (10 tables, 50M records total). Issue: During the Index Rebuild (~20 minutes), we fail to insert data into the DB ...
3
votes
1answer
799 views

Oracle explain for cascading delete is wrong

My deletes in Oracle 11 are very slow. The tables are linked by foreign keys and every foreign key constraint has a delete cascade set on it. If I hit the explain button on a statement like this ...
2
votes
1answer
324 views

what does SHOW /*!50000 GLOBAL */ STATUS do ?

What is the difference between SHOW /*!50000 GLOBAL */ STATUS and SHOW GLOBAL STATUS I saw that in few scripts and tuning presentations the first command is being used. Is there a difference, ...
5
votes
2answers
138 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 ...
9
votes
2answers
6k views

Percona vs MySQL

What is Percona? How does it differ from MySQL? When should we consider switching (or upgrading) from stock MySQL to Percona? To add some specifics in our situation we almost exclusively use ...
2
votes
1answer
1k views

Performance Inserting and Updating Millions of rows into a table

We have a CSV the user imports into the Application. After inspecting the CSV, validating and applying some business logic, we got Inserts and Updates operations we should perform into a ...
1
vote
2answers
803 views

SQL Server 2008 R2 Express high insert slowdown possibly due to PAGEIOLATCH_SH

I have a program that insert row to a table though multiple connections. For each insert, the connection would open and then close. When I run the program, the insert were fast. However, once it reach ...
5
votes
2answers
2k views

How do I get the execution plan for a view?

I have a schema with a number of views. I need to check the execution plans to make sure the appropriate indexes are in place and being used. How do I do this? I'd rather not have to copy and paste ...
3
votes
1answer
1k 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 ...
4
votes
1answer
11k views

SQL Server Activity Monitor - Resource Waits - Logging > 1400 ms/sec, how?

I have an SQL Server 2008 R2 server. I open "Activity Monitor", and inside the "Resource Waits" category, I see that the "Logging" category is taking up more than 1400 ms/sec. That doesn't seem to be ...
6
votes
2answers
7k views

SQL query slow-down from 1 second to 11 minutes - why?

Question: I'm porting the below query (listing tables by foreign key dependencies) to PostGreSql. WITH Fkeys AS ( SELECT DISTINCT OnTable = OnTable.name ,AgainstTable = ...
1
vote
1answer
281 views

How should I distribute my tables for better performance from fragmentation point of view

I have a database on SQL Server 2008 R2 with about 20 non-indexed tables that are continuously undergoing INSERTs AND DELETEs. There are about 400,000 records @ 4KB/record being inserted or deleted ...
4
votes
2answers
2k views

“freeing items” taking forever on inserts, updates and deletes

Recently I migrated all my MySQL database tables from MyISAM engine to InnoDB. I'm using the DotCloud MySQL service as my server (http://docs.dotcloud.com/services/mysql/). After the migration, ...
2
votes
1answer
1k views

Postgres multiple joins slow query, how to store default child record

Ive got a small database in Postgres, about 10,000 records storing company customers. I have a "slow" performing query (about half a second) which is performed very frequently, and my boss wants me to ...