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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Mysql table with only two columns, nothing unique: Will an index increase search performance?

If my table only has two columns (username, groupname) and a million or so rows, will an index improve performance at all? Wouldn't it take just as long to search the index file as it would to search ...
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1answer
105 views

Partition : understanding files and file groups

We are trying to partition a large history table. Being new to partitioning, I was trying to understand the concept of files and file groups. File groups can be set up in following three ways : 1. ...
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1answer
17 views

How performance schema in mysql 5.6 improve performance?

Since MySQL 5.5 performance_schema database has been added likewise information_schema. As we know that tables in information_schema contains statistical information like tables, plugins, partitions, ...
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16 views

MySQL 5.5, Xubuntu 14.04 - INSERT and UPDATE bottleneck

DBAs: I have been developing and maintaining plugins for Moodle for the last ~2 years, and have recently decided to try using my local desktop again, rather than my institutions ESX VMs, as a ...
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6 views

Sysadmin tools for SQLAnywhere

I'm seeing a performance issue in a 3rd party application based on SQLAnywhere 7. The DB engine seems to be dramatically underperforming on the hardware provided. It seems to have a upper limit on the ...
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1answer
75 views

How to configure my.cnf for Mysql 5.1, which is using too much CPU?

I am new Database engineer. I am having trouble in my server which is using too much CPU on database query(simple count statement). I have googled about it, so i found out it depends on system ...
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1answer
22 views

MySQL ON DUPLICATE KEY UPDATE performance issue

We have a table with over 200k rows. Every row belongs to a category, there are almost 50k rows per category. What is the best way to update all rows of that category? We are using a script like ...
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1answer
27 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
883 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
52 views

MySQL: How to avoid case sensitivity in SQL queries when migrate from Windows to Linux?

I have migrated my Database from Windows to Linux server. In many places, query has been written without focusing their cases (uppercase / lowercase). So, these queries are not getting executed and ...
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2answers
68 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
46 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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30 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
210 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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1answer
63 views

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

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 ...
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5 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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24 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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2answers
136 views

Enhance performance of update query

I have a query that is running against a table with 50 million rows. The phone number is stored as a CHAR(10) and an ETL process is changing the phone number if it has certain values. We are seeing ...
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1answer
27 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
94 views

DB disk space requirements comparision between MySQL versions

I have 2 labs where MySQL is installed. DataBases are created and deleted dynamically by certain internal processes. InnoDB is the Engine used. In one lab, MySQL version 5.0.77 is installed. The DB ...
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1answer
126 views

Inserting to table: Insert rows with Left Outer Join or Insert rows then Update?

I have a table of Orders and another table of Deliveries. The Orders table will contain a reference to the Deliveries table if there is a corresponding row. Not every row in Orders will have a row in ...
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1answer
40 views

Does having a big table that I do not query cause the whole DB to be slower?

I have a log table that I use for logging files sent to clients. I'm not querying that table, just use it for logging (INSERT) and when I need to check when something was sent to clients, usually once ...
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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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19 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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2answers
134 views

mysql need help optimizing query

I have a table containing servers logs, and another table containing rules to match certain and drop them. The logs tables contains around 1 million rows, and there are about 20-30 rules. The ...
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1answer
177 views

Major Discrepancy Between SQLIO IOPS/Throughput Stats and DBCC CHECKDB Operations

I'm conducting time trials on a new SSD array running both SQLIO tests and a real-world workload of DB restores and DBCC CHECKDB calls. I'm seeing a major discrepancy between the IOPS and throughput ...
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44 views

How to prepare executon plan for given sql query on a server with 4 processors (Oracle database)

4 processors means the query runs in parallel. Select /*+ parallel(4) */ T1.A FROM T1,T2,T3 WHERE T1.A = T2.A AND T1.B=T3.B AND T1.C=T3.C Tables T1,T2 and T3 have 4,8, and 16 partitions ...
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1answer
26 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
32 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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1answer
24 views

MySQL 5.1: change datadir variable value in my.cnf

Below is my system configuration: OS: RHEL5 MySQL: 5.1.73 Default datadir=/var/lib/mysql/ But, the above directory has space crunch. So, I decided to change the path. I found /u000 directory has ...
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13 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
501 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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10 views

JDBC , make connection static to improve performance [migrated]

I'm dealing with JDBC these days, I found it's really slow and i try to figure out some ways to improve the performance, I've noticed that it's slow to get the Connection object, so I'm thinking ...
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1answer
48 views

DB2 - how to track IOPS statistics?

DB2 9.7. Is there some easy way in every moment go have statistics about IO operations per second? I am not interested for hit ration on Buffer Pool but really on IOPS? THANK YOU
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1answer
48 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
78 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
3k 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
30 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 ...
2
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1answer
48 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
28 views

Mysql improve Self join performance large table?

I have a task to help identify conflicting IP ranges , I want to highlight when one companies IP range falls within another's ... below is the sample table, I have converted the IP ranges from .dot ...
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1answer
42 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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2answers
191 views

Minimizing Indexed Reads with Complex Criteria

I'm optimizing a Firebird 2.5 database of work tickets. They're stored in a table declared as such: CREATE TABLE TICKETS ( TICKET_ID id PRIMARY KEY, JOB_ID id, ACTION_ID id, STATUS str256 ...
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1answer
37 views

Slow INSERT/UPDATE on InnoDB

I have a problem with the performance of my MySQL server, let me explain: I instaled a MySQL server, version 5.5.20 Server version: 5.5.20-log Source distribution SELECT queries runs fast on ...
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1answer
25 views

How can I measure the number of IOPs for a certain query

I need to estimate the max IOPs for a certain MySQL DB (one that does not exist yet). The OS is Linux and the DB is MySQL 5.1.x (though I don't think the DB brand is important for the asked topic) ...
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0answers
54 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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31 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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1answer
38 views

Preventing sysquerymetrics from being created ASE 15.7

Can I prevent Sybase ASE 15.7 from creating the sysquerymetrics view for a database upon creation? And also, if the view is dropped how can it be added later?
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24 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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1answer
112 views

MySql - is possible that performance issues are caused by dynamic SQL?

We have this MySQL SP, which uses dynamic SQL. It seems it does NOT perform well under load. It is possible that this SP becomes slow under load because it uses dynamic SQL? Can dynamic SQL cause ...
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2answers
134 views

Improving a search query

I have a query for search function. Basically search function allowed user to define what they "have" and "want". Then this query will filter out all the possible result which created by other user. ...