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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InnoDB Performance Tuning

I'm new to database administration so please excuse any omissions of what would seem like basic info to provide for this problem. I'm a RoR developer and our team is currently short a DBA, so we're ...
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1answer
45 views

In real terms, how much effect does a bad fillfactor have on performance?

There's a storm brewing, or maybe I should say firestorm. A customer has recently implemented SQL Server 2012 Always On but that's not the most important bit. A list of fires to be put out has been ...
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2answers
5k views

Why does MySQL (InnoDB) table get faster after OPTIMIZE TABLE, but then don't work?

I have a Django web application that stores data in a MySQL InnoDB database. There is a particular page that is accessed a lot on the django admin, and the query is taking a long time (~20 seconds). ...
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5answers
245 views

How to shard 14 gb of data for archival database?

We have 14 GB worth of CSV's containing product information, with each CSV being all the records for a US state. We now want to store this in a database. There would be ~130 million records. The ...
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1answer
773 views

Tune postgres 9.1 to speedup deletes

I need to tune my postgres db to speed up delete queries. I cant't optimize my db structure yet, so I'm looking for options available on server level for postgres 9.1. I've seen in older posts the ...
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1answer
117 views

why/how does the number of matched columns influences the way of excecuting a query

Imagine the following situation: Table A uses MyISAM and contains 4 fields (text) with a combined FULLTEXT-index. FULLTEXT fulltext1 | fulltext2 | fulltext3 | fulltext4 Table B uses InnoDB and ...
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3answers
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whether a big (but not used) ibdata1 slow anything down

Hi I have an ibdata1 that is around 10 gig. I have gradually migrated to 'file per table' using the innodb_file_per_table=1 option such that there are no big tables in ibdata1 anymore. I recently ...
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3answers
563 views

Tuning Question

Every so often our box is HAMMERED to a crawl %Wait goes to 40 or 50% and connections grows to 300 or so. i think its due to a query running, but i wanted to see if any of the settigns on the mysql ...
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289 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, ...
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1answer
923 views

SQL Server Replication causing locks on table

we have three MSSQL 2005 servers (database is set to compatibility level 80 for legacy reasons) which we have just set up Transactional Replication w/ Updateable Subscriptions on. Two which are ...
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1answer
27 views

3 minutes to import 327Mo database

We do database import a lot of times per day on a server with those specs : Xeon E5-1620v2 4c/8t @ 3,8Ghz 32 Go DDR3 ECC 1600MHz Hard Drive 2x 3 To SATA3 MariaDB 10.14 with XtraDB Given a 327Mb ...
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2answers
98 views

Seeking help to test a use case on sql server memory

This is a question which came out of curiosity to know of how sql server handles memory. Assume I set a very low value for max server memory and I increase my workload like running dbcc checkdb, ...
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1answer
123 views

Need help tuning my.cnf file

I need help tuning mysql. Currently it is using a lot of CPU. I dont find any query that last longer than 3 seconds in SHOW PROCESSLIST and there are only around 20-25 running most of the time. Still ...
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2answers
88 views

Does having many databases affect MySQL performance?

I have huge unused databases in MySQL. Do they affect my MySQL engine performance even if they are unused? Do they consume memory on their own? Thanks
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1answer
84 views

How to monitor load on database server

Could anybody please suggest me a way to monitor the load on my database server? What perfmon counters should I monitor on daily basis and confirm that load on the server is increasing day by day [or] ...
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3answers
395 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
93 views

Why isn't the rows of an EXPLAIN accurate?

I have the following table: mysql> select count(*) from employees; +----------+ | count(*) | +----------+ | 10000 | +----------+ 1 row in set (0.03 sec) I do an EXPLAIN: ...
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1answer
94 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
227 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 ...
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1answer
73 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
331 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 ...
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2answers
3k 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 ...
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1answer
1k 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 ...
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1answer
237 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
318 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 ...
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1answer
207 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 ...
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1answer
115 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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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
199 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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1answer
491 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 ...
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1answer
72 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 ...
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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
148 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
88 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
669 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 ...
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1answer
141 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 ...
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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 ...
2
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1answer
279 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 ...
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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
551 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), ...
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2answers
973 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
925 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 ...
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1answer
461 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)?
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1answer
683 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 ...
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2answers
488 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 ...