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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160 views

Understanding pagefile.sys % Usage performance monitor (perfmon) counter correctly

Lately we run into performance inssues and I started tracking some recommended sql, memory, disk and cpu counters. I informed myself about the recommended values and numbers to look at. One of the ...
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1answer
2k views

Lazy Writes Performance Issues

My SQL Server sometimes reports high Lazy Writes e.g. "Lazy Writes per second is 119 Writes/sec" What should I be checking to find out why this is high? What are potential causes? Thanks.
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2answers
79 views

Why is this simple join taking so long?

I'm trying to run some reporting queries on a MySQL database, and I'm running into serious performance issues for some reason. One table, page_views, is extremely large (~70 million records), so some ...
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2answers
69 views

Are #tables and #procedures 'not best practice' or 'bad practice'?

I am working on a project and part of it is an interface tool that executes SQL code stored in a xml file to import/export files. In the file, temp procedures and temp tables are used quite heavily ...
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1answer
46 views

Detailed optimal column order with large text and bytea

I read this excellent answer on optimal column ordering and noticed the summation: Generally speaking, if you put the 8-byte-types first then the 4-byte-types and the 2-byte-types last you can't ...
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2answers
352 views

Ideal values for wait time in SQL server

This is related to my own post here The SQL server starts everyday at 8:30 AM and stops around 9:30 PM.( So wait times will reset everyday) SQL server will be used by around 60 users ...
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15 views

Page cache installation in magento admin panel

Hi just added pagecache from varnish in Magento through the magento connect. It went in ok, just wanted to know, the correct configuration. In magento admin panel for the correct set up in the page ...
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62 views

Performance: Interleaving several statement handles in MySQL

Does interleaving several statement handles slow the system down? Example (Perl): $sth1->execute(...); $sth2->execute(...); $sth1->execute(...); $sth2->execute(...); (interleaved) vs ...
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1answer
47 views

Two MySQL requests at the same time - Performance issue [closed]

I have a MySQL server with many innodb tables. I have a background script that does A LOT a delete/insert with one request : it deletes many millions of rows from table 2, then insert many millions of ...
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1answer
2k views

Qcache_free_memory not full yet I get alot of Qcache_lowmem_prunes

I just started dabbling with the query cache for our CMS. Can anyone tell me (or at least give a good guess) why I get a lot of Qcache_lowmem_prunes when more than half of Qcache_free_memory is free? ...
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0answers
121 views

Optimization Tips For MYSQL Tuner/Primer

So I have a site that has a crap ton of traffic. I see a decent amount of latency when the site has over 1,000 active visitors on it. I have new relic installed and it seems Im only using 10% of the ...
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1answer
30 views

Need DDL for an Oracle Table that would be 1 row = 1 8K Block

For performance testing in our performance environment we want a means to turn over SGA the way production does. Our performance environment is a fraction of production and production's very nature ...
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1answer
38 views

MyISAM InnoDB performance

MyISAM vs InnoDB I keep reading how InnoDB is faster than MyISAM. I wanted to find out myself. When I was using a forloop in PHP to fill my MySQL test database with 100,000 numbers using PDO driver. ...
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29 views

Excesive use of RAM on MysqlServer

The RAM of a server where I have installed mysql is always 100% and looking at the processes that are running, MySQL is the most consumer on CPU and memory and I can see the cause of great use RAM.   ...
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5answers
560 views

Performance tuning a Great Circle distance calculation

I have a query that I am using to find locations that are within 1km of a known point. To do this, I am using the Spherical Law of Cosines formula with my latitude and longitudes. Currently, the ...
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1answer
111 views

How to deal with async calls to a stored procedure that updates data

I have asynchronous calls from Entity Framework to a stored procedure. The stored procedure selects data to a temp table and later on, it updates the real table. This works fine for sync calls. The ...
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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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2answers
4k views

Most efficient way to add a serial column to a huge table

What's the fastest way to add a BIGSERIAL column to a huge table (~3 Bil. rows, ~ 174Gb)? EDIT: I want the column to be incremented values for existing rows (NOT NULL). I didn't set a fillfactor ...
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2answers
33 views

Do I need foreign keys in ORMs?

Object Relational Mapping (take ActiveRecord and Rails, for example) allows a programmer to define relations between models, and callbacks on delete. So my question is: do I still need to define ...
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1answer
98 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 ...
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1answer
62 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" ...
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0answers
71 views

Performance issue in Postgresql9.3

I have very good configuration server dedicated only for PostgresSql. Server is 16 Core 122 GB RAM on Linux machine. select version(); **PostgreSQL 9.3.4 on x86_64-unknown-linux-gnu, compiled by gcc ...
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38 views

Guidelines on best indexing strategy for varying searches on 20+ columns

I’m running a search engine for cars. It’s backed by a postgresql 9.3 installation. Now I’m unsure about the best approach/strategy on doing index optimization for the fronted search. The problem: ...
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0answers
29 views

Extended Events missing documentation

I have been looking pretty hard for the documentation regarding the RingBufferTarget <RingBufferTarget truncated="0" eventsPerSec="1370714" processingTime="7" totalEventsProcessed="9595" ...
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0answers
17 views

View in View slower to execute?

Sometimes it's easier and clearer arranged to create a View from another View. Can this cause some speed losses in relation to selecting everything just in one Big and long View-Command?
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1answer
33 views

Transforming Huge Database table to Another Table

We are migrating lot of data from our old database to new database. Presently, both of them are actively[writing/reading] used based on flows/activity as migration is in progress. Here's the real ...
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0answers
25 views

Performance tuning in Sybase

Does Sybase have a tool like AWR in Oracle which can be used to identify high load SQL, tell the important waits that are happening, help in understanding the workload? What are the main tools to be ...
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1answer
79 views

Running queries directly on DB2 databases

Just have a general query, if it is really fine or safe to run long select queries on RDBMS production Databases specifically DB2? If NO, what are the major risks and issues in executing select ...
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1answer
33 views

MySQL 5.1: How to rollback partitioned table

I have partitioned a table on the basis of one flag column have value either 0 or 1. Now, I want to roll back these tables. How can I do this?
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2answers
5k 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 = ...
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0answers
25 views

Database slowdown at random times using mirroing

Our web application suffers DB query timeouts a few times a day at random times. Can you help to work out the cause, e.g. deadlocks, mirroring (disk or network), etc? We have two identical database ...
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1answer
56 views

Insert (write) performance

We are trying to speed up the queries in our application and in the process identified all queries which took more than 100ms. We noticed that there were few insert statements which took more than ...
2
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0answers
165 views

SQL Server 2012 Local SSD TempDB Slow

I have a production deployment using local SSDs for tempDB. I have 2 SSDs in a RAID1 configuration. I am seeing average reads of 1-2ms but the average writes are showing as 1377ms on all four of my ...
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1answer
476 views

SQL Server 2008 R2 Express single CPU core usage and need of upgrade to SQL Server 2014 Express

In our office we are using SQL Server 2008R2 Express which is installed in Windows server 2012. The SQL Server database is accessed by more than 60 users in network simultaneously. In recent days we ...
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1answer
64 views

Slow queries InnoDB occasionaly

I have the next table: CREATE TABLE `sessions` ( `session_id` char(32) COLLATE utf8_unicode_ci NOT NULL, `session_expires` int(11) NOT NULL DEFAULT '0', `session_data` varchar(10000) COLLATE ...
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0answers
46 views

How can I reduce recursion in Couchbase?

Sometimes, you need to access a certain document (A), but you do not know the key for that document (A), as that data is stored in a different document (B). So now, if you want to fetch A, it looks ...
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1answer
42 views

How to optimise very simple query with subquery that only needs to execute once

SELECT products_id, products_model, products_iban_no, products_allocation_number FROM products WHERE products_model IN (SELECT products_model FROM products GROUP BY products_model HAVING ...
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0answers
118 views

Do OR conditions in Oracle SQL queries spoil index use / cause full table scan?

I have a query on Oracle 11g of the following type, which results in a series of highly inefficient full table scans: select t.Id, t.ObjectId, t...[other Tasks columns] , od1...[ObjectData1 ...
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1answer
57 views

Redo log size results into performance degrade

We are continuously doing heavy insert and update query, but after 10 hours data base is returning answer late in minutes normally it takes around 1 ms. I observed that "free buffer wait" and "redo ...
3
votes
1answer
306 views

Slower queries after upgrade from mysql-5.5 to mysql-5.6

There is lots written about how MySql 5.6 is faster than MySql 5.5 (e.g. http://dev.mysql.com/tech-resources/articles/mysql-5.6.html) but we upgraded our Amazon RDS instance (using the new upgrade ...
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1answer
284 views

How to know which process is causing high memory usage on DB?

I've got one Onesight alert mail stating below: Short Description: Onesight Alert: ZEUS DB Monitor (zeus04) Description: Solaris 5.8: vmstat memory(free) - Free Memory for zeus04 2065112 8:06:02 ...
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1answer
158 views

Slow delete caused by many foreign keys

My DB has about 90 tables. Most of the tables have an UpdatedBy and AddedBy column that have foreign keys pointing back to the user table. With even moderate amounts of data spread throughout the ...
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0answers
22 views

Approaching multiple values in same column

I'm developing an Android-application that scrapes the schedule for my university and presents it nicely since the current system is a nightmare. I'm processing a lot of data and it gets down to ...
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1answer
59 views

MySQL from table to table data transfer

I've got some problem with my MySQL. I have the database with many many data. Well, there is only one table actually with huge ammount of data, over 1 billion rows. For some reasons I need to create ...
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0answers
18 views

Storing generated documents that can not be updated by changes in relationships

I have a system running with PostgreSQL and Yii Framework, which generates a few medical documents that, once ready, can't be changed. For example: If my full name comes out on this document today, ...
3
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1answer
148 views

How un-clustered is a CLUSTER USING table in PostgreSQL

I have some tables which benefit greatly from CLUSTER ON/CLUSTER USING in Postgres SQL: # CLUSTER table USING index_name; # ANALYZE VERBOSE table; # CLUSTER VERBOSE; A maintenance task periodically ...
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0answers
21 views

What is the best type of database for numerous multi-threaded access? [closed]

I am developing a simulation and have limited experience working with databases (very limited SQLite3 exposure). Here is my task: Server that stores a potentially large database (no size requirement ...
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2answers
52 views

SQL Server Backup and Query Execution

Is SQL Server Backup affects the query execution performance? Is there an effect while running the SQL Server backup in remote query execution? Thanks.
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3answers
352 views

best practice for 'staging' relation in stored procedure: use temp table, or view?

When I write stored procedures that take relation A and output relation Z, I like to create 'staging' relations along the way, so I can inspect the state of the data after each step in the programming ...
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0answers
36 views

Oracle 9i Low performance on Windows Server Enterprise 2003

I'm facing some problems with performance with my Oracle database running on a virtual machine with Microsoft Windows Server Enterprise 2003 with 8GB RAM. It works pretty well after the database is ...