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.

learn more… | top users | synonyms

1
vote
2answers
387 views

Slow queries on SQL Server [closed]

We have SQL Server 2005. Our main table is the archive table which has nearly 200 million rows in it. There are 2000 clients that connect a service so the service writes the information to the ...
1
vote
1answer
66 views

SQL - Need some advices for building a large db

currently, as I understand, to build a large db, we need to pay attention to its size and performance. Below are what to reach: Size: HDD has > 4tb to store filegroup if using partition tables. ...
2
votes
1answer
292 views

How do you figure out what planner cost constants to use in Postgres?

I'm using Postgres 8.4 right now. Performance has started to become an issue as our tables have grown in size and our queries in complexity, so I've started to look into some performance tuning, but I ...
2
votes
1answer
1k 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 ...
7
votes
2answers
4k views

What are the differences between SQL I/O Sim and SQL IO tools?

I want to test my different SQL Server alternatives with a benchmark tool. I found two tools by Microsoft: SQLIO Disk Subsystem Benchmark Tool SQL IO Sim What are the differences between them? is ...
4
votes
4answers
627 views

Can I reorganise index on a sql server 2005 database without performance hit on production server

I would have preferred to run online index rebuild instead but our production sql server (2005) is standard edition. Hence I think I am left with reorganising index and update statistics after that. ...
3
votes
2answers
925 views

Are these MySQL queries efficient?

It took me quite a while to learn how to deal with timestamps in MySQL and I think I accomplished my goals, but I want to double-check two things: 1) Are these doing what I expect 2) Are there ...
21
votes
5answers
19k views

What is the most efficient way to get the minimum of multiple columns on SQL Server 2005?

I'm in a situation where I want to get the minimum value from of 6 columns. I've found three ways so far to accomplish this, but I have concerns with the performance of these methods and would like ...
2
votes
1answer
125 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 ...
6
votes
3answers
3k views

Is MariaDB a suitable drop in replacement for MySQL on a standard LAMP stack?

I've been wondering lately what (if any) are the improvements available in MariaDB over 'conventional' MySQL? I understand that where platform interoperability and/or backwards compatibility may be ...
6
votes
1answer
4k views

Why is DELETE so much slower than SELECT, then DELETE by id?

I have a fairly busy InnoDB table (200,000 rows, I guess something like tens of queries per second). Due to a bug I got 14 rows with (the same) invalid email addresses in them and wanted to delete ...
0
votes
1answer
2k views

mysql closing tables taking double the time of process

I have a delete query that is taking a long time. When I check in processlist that status is showing as closing table. It is taking a long time to close tables. ex: I run a query and the total time ...
3
votes
4answers
7k views

mysql insert into indexed table taking long time after few million records

I have a table like this CREATE TABLE IF NOT EXISTS `dnddata` ( `numbers` varchar(10) NOT NULL, `opstype` char(1) NOT NULL, PRIMARY KEY (`numbers`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 ...
5
votes
1answer
723 views

Denormalized table designs in normalized database?

There was a discussion between the developers and DBA's last week on set of tables that the developers were creating with more than 400 columns in our OLTP environment with combinations of VARCHARs, ...
9
votes
3answers
14k views

How to get the most out of MySQL on a QuadCore machine with 16 GB of RAM?

I'm running a MySQL 5.5 server on my workstation for scientific data analysis and wonder how to configure MySQL in order to get the most out of it performance-wise. The types of query that I typically ...
3
votes
1answer
244 views

Why are my queries getting really slow?

I own a WordPress installation, and Updated to 3.4.1. After the upgrade, I experienced a very strange slow-down. After all, I used the define('SAVEQUERIES', true); in my wp-config.php with ...
2
votes
3answers
1k views

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 ...
15
votes
4answers
15k views

Aggressive Autovacuum on PostgreSQL

I'm trying to get PostgreSQL to aggressively auto vacuum my database. I've currently configured auto vacuum as follows: autovacuum_vacuum_cost_delay = 0 #Turn off cost based vacuum ...
4
votes
1answer
3k views

PostgreSQL tree structure and recursive CTE optimization

I'm trying to represent a tree structure in PostgreSQL (8.4) to be able to query the path from the root to a given node or to find all the nodes within a sub-branch. Here is a test table: CREATE ...
6
votes
3answers
6k views

Should I add an arbitrary length limit to VARCHAR columns?

According to PostgreSQL's docs, there's no performance difference between VARCHAR, VARCHAR(n) and TEXT. Should I add an arbitrary length limit to a name or address column?
0
votes
0answers
42 views

Resource to learn writing most efficient and highly optimized sql queries [duplicate]

Possible Duplicate: Learning to Optimize SQL Queries and Understand Execution Plans - Resources? Can some one point me to a great book/great books or some really solid reference/references ...
6
votes
2answers
27k views

way to prevent queries from waiting for table level lock

We've encountered a problem after moving the database of our customer to an extra server. This should have had positive effects on the site's performance, but there is a problem with table locking in ...
0
votes
1answer
300 views

Fill factor for later bigserial + index

I'm planning to import and update a huge table (3 Bil. rows) in the following step: create table with fill factor x import the data from csv files (6 files, ~21GB each) add a BIGSERIAL column create ...
2
votes
2answers
1k views

Why are parallel writes in MySQL as slow as sequential writes?

I have many MySQL write-only processes. They all go to the same MySQL master. I run them sequentially to get a baseline time. I basically chain together several mysql command-line clients, ...
1
vote
1answer
307 views

Should indexes automatically be placed into their own bufferpool?

We work with DB2 LUW (specifically we are currently on 9.7 FP4) running on AIX. Per best practices from IBM, they recommend that when you build a table, you place the data, the indexes, and LOBs/LONG ...
1
vote
1answer
608 views

What is connection time?

We are currently trialling ManageEngine SQLDBManager Plus. On the dashboard for a server it shows connection time in milliseconds (currently 15ms). Can anyone tell me what Connection Time represents ...
5
votes
3answers
2k views

CPU usage on RDS instance monotonically increasing with no change to query volume

I have two RDS instances: a R/W master and a read-only replica. On 29th June, the replica stopped registering replication data - not sure if this is related. On July 3rd, the master's CPU usage ...
2
votes
2answers
8k 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 ...
0
votes
1answer
1k views

Slow performance of MySQL Join Query

I have inherited a site (running Coldfusion8 and MySQL 5.0.88) with a product search using multiple criteria. I'm struggling with optimizing the search, especially a pricelist check, which makes the ...
1
vote
1answer
861 views

decreased performance of stored procedure when migrated from mysql server 5.0 to 5.5

i recently testing the move of our db from one server to another. as part of this process i copied all the data to the new db and started testing it. as a comparison i run a store procedure whose ...
3
votes
2answers
1k views

SQL Server 2012 - Frequent SELECT and UPDATE on bit column. Index doesn't help

I have a SQL Server table with about 2 million rows in, this table stores short textual documents. Here's my schema: CREATE TABLE Documents ( documentId bigint IDENTITY NOT NULL, content ...
3
votes
2answers
3k views

How to setup mysql on tmpfs?

How to setup mysql on tmpfs ? I am reading a tutorial in french, where the author do it this way : 1.) Create a tmpfs directory : mkdir /var/tmpfs mount -t tmpfs -o size=1G tmpfs /var/tmpfs chown ...
3
votes
2answers
3k views

Oracle listagg forces SORT (GROUP BY) execution plan

I have the following query SELECT /*+ USE_HASH_AGGREGATION */ id --, count(id) , listagg(type, ', ') within group (order by null) types FROM test group by id Both type and id are short strings. ...
2
votes
1answer
3k views

mysql taking too long to send data

I have a simple table with million of records (14,000,000) and for a simple query it is spending too much time "sending data". The table CREATE TABLE IF NOT EXISTS details ( id int(11) NOT NULL, ...
2
votes
2answers
214 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 ...
7
votes
1answer
4k views

Capabilities of InnoDB INSERT Performance

Hi I am running the most recent version of Percona Server. Server version: 5.5.24-55 Percona Server (GPL), Release 26.0 I have a 10 cpu box of these characteristics. processor : 0 vendor_id ...
10
votes
2answers
964 views

Strategy to handle an SQL Server DB with too many files (BLOBs) in it?

Scenario: SQL Server 2005 database servicing an ASP.NET application (on a separate web servers). Database: DB has about 5GB of "normal" data in it, and about 15GB of "files" (e.g.: a 200k PDF stored ...
197
votes
15answers
77k views

Can MySQL reasonably perform queries on billions of rows?

I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies ...
5
votes
2answers
445 views

Create function in central database or repeat in each database?

One of my developers has written a SQL function that works like the VB.Net function (LastIndexOf) and wants to publish it. My question is what would be the reason to put this in a central database ...
2
votes
1answer
168 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 ...
4
votes
2answers
5k views

Primary key vs. unique index: performance difference with foreign keys?

Will there be any difference in performance if you compare a query fetching data via a join between two tables where there's a relationship against either of the following: A primary key A unique ...
9
votes
2answers
10k views

Slow Performance Inserting Few Rows Into Huge Table

We have a process that takes data from stores and updates a company-wide inventory table. This table has rows for every store by date and by item. At customers with many stores, this table can get ...
0
votes
2answers
1k views

Some queries slower in MySQL 5.5 than 5.0?

We have an exceptionally inefficient process (1.3 million selects, 232k updates) that I'm now recoding to be 1 select and 50 updates. In the meantime, though, today's process ran. We recently updated ...
6
votes
2answers
751 views

What are the pros/cons of splitting date and time into separate fields vs. using the datetime data type and storing the date in a single field?

My database is extremely large and growing at a rate of ~20m rows/day. I have timestamp data that is important but most of the reporting is based on date ranges and week over week or month over month ...
3
votes
1answer
272 views

Adding new key(s) to enable partitioning, INSERT performance?

I have a table to storage GPS coordinates with multiple (~30) inserts per second (from 50 different devices) during 12 hours per day, so the table is growing fast, to improve the SELECT speed I was ...
1
vote
1answer
295 views

Database inserts/updates slow only in Production

We have a int/test/staging/production Mysql database setup. A Java application(using Hibernate) that periodically generates up to 200,000 updates/inserts (mainly updates by 20 to 1) completes in 10 ...
6
votes
1answer
1k views

What should every DBA know? [closed]

As a SysAdmin who "wears all the hats", I find myself increasingly pulled into database projects. I took one database course back in college and since then I've always scoured resources online (like ...
6
votes
2answers
2k views

Slow ORDER BY with LIMIT

I have this query: SELECT * FROM location WHERE to_tsvector('simple',unaccent2("city")) @@ to_tsquery('simple',unaccent2('wroclaw')) order by displaycount I'm happy with it: "Sort ...
1
vote
1answer
183 views

Hard Drive Configuration for my setup

I have a fairly large transactional database (100GB) with a lot of users. The database access is solely via stored procs that make heavy use of temp tables, table variables, cursors and other fun ...
5
votes
1answer
2k views

NESTING_TRANSACTION_FULL latch

Production SQL Server 2008 performance is far below expectations. Simple single-table queries sometimes are working for 5 seconds in the mid-day compared to 250ms after hours. We cannot find which ...