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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12
votes
4answers
4k views

Is it possible to increase query performance on a narrow table with millions of rows?

I have a query that is currently taking an average of 2500ms to complete. My table is very narrow, but there are 44 million rows. What options do I have to improve performance, or is this as good as ...
10
votes
2answers
822 views

Postgres query plan of a UDF invocation written in pgpsql

It's possible when using the pgadmin or plsql to get a hold of a query plan for a sql statement executed via a UDF (using EXPLAIN). So, how do I get a hold of the query plan for a particular ...
31
votes
5answers
17k views

Why not use a table instead of a materialized view?

I'm new to Oracle databases. If I have understood correctly, materialized view is a view which result set is saved as a physical table in the database and this view/table is refreshed bases on some ...
1
vote
3answers
922 views

Improve performance of a Fact Table

I have a Fact table CardTransactionFact Table Structure TABLE [dbo].[CardTransactionFact] [CardTransactionID] [int] IDENTITY(1,1) NOT NULL, [TransactionTerminalID] [int] NOT NULL, ...
2
votes
2answers
3k views

Querying a database efficiently for a huge chunk of data

Here is my query SELECT * FROM ( SELECT a.*, rownum rnum FROM ( SELECT id, data FROM t ORDER BY id ) a ...
7
votes
2answers
269 views

High rise in SQL Server CPU after adding a DB

I have just added a "new" DB to my Server (2005), I have restored from a dead SQL2000 server to my active one (2005), and changed the compatibility to 90 (SQL Server 2005). My average CPU was on 48% ...
11
votes
2answers
3k views

Placing Transaction Log on Separate Volume [solid state]?

Transaction logs are often isolated on a separate volume. The rationale for this practice, as I understand it, is that the transaction log's data is written sequentially -- and hard drives can execute ...
8
votes
2answers
2k views

Why you want to avoid Dynamic SQL in stored procedure?

I have heard one said you do not want to use Dynamic SQL. Can you give some concrete example or real-life example? Personally, I code it a few times in my database. I think it is OK because it's ...
6
votes
2answers
2k views

How can I save a severely fragmented database/table?

I've recently made a discovery that might explain my slow SQL run times. I found out that the default in SSMS is to allow mdf growth of 1MB at a time. When the size of one table alone is roughly 23 ...
4
votes
3answers
1k views

What should I consider when deciding between passing a comma-delimited string to a stored procedure instead of calling it individually per record?

I have to run the same stored procedure for a lot of records (hundreds or thousands, depending on user selection). The procedure is fairly basic: insert a record in two separate tables with some ...
6
votes
3answers
7k views

How database size affects performance: Theory vs reality

There is a lot out there that says database size should not affect performance to any great degree. As long as indexes on tables fit in memory the database should remain performant. However what is ...
3
votes
1answer
7k views

Amazon RDS MySQL 5.5 Innodb Lock wait timeout exceeded

Ever since we've moved to Amazon RDS, we've had some pretty crazy performance issues, and today we started having locking issues. Because of that, I figured it was just a timeout issue, and went to ...
1
vote
1answer
161 views

Optimizing table and choosing storage engine

Having the follow MyISAM table: +----------------------+-----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
6
votes
2answers
2k views

Rebuilding index has impact on mdf/ldf files SQL Server 2008

While rebuilding index have used option 'SORT_IN_TEMPDB = ON' in order to avoid unnecessary growing your user database files. What does it exactly means? Is complete process done on TempDB and does ...
4
votes
1answer
6k views

Analysing SQL Server Network I/O

A frequent request I get from clients is to help figure out what queries or clients are making the largest contribution to SQL Server saturating an Ethernet link. Ideally I'd look at some counters ...
3
votes
1answer
777 views

Fastest way to copy data from MyISAM to InnoDB

I want to copy all data from a MyISAM table with 16 millions rows to a InnoDB table, that will have a different (optimized) schema. See tables below to see the changes. However, every approach I try ...
6
votes
3answers
1k views

Performance of Inline-TVF vs. Views

I have a database where i am using inline TVFs (table value functions) instead of views. For example, I might have two tables called [car model] and [car manufacturer] that I'm joining together ...
0
votes
1answer
796 views

Performance comparison in ways a SSIS package can be run

I'm wondering if there is any difference in performance of a SSIS package if it runs using SQL Server job, vs running using DTEXECUI.EXE Utility or running in BIDS? Also if the target database in on ...
2
votes
2answers
292 views

Writing to a DKNF database, but reading from a de-normalized table for performance?

Would the following approach be reasonable? The Goal: queries have to be relatively fast, but without the hassles incurred by writing to a de-normalized database. The Context: A database for ...
1
vote
3answers
91 views

Generally speaking, what pecking order should be used when tuning SQL Server?

When tuning SQL Server, what generally is the pecking order to use when trying to decide what to tune first? I'm asking in regards to an existing database that would I would have little ability to ...
5
votes
4answers
3k views

How can I speed up “show columns” on MySQL?

My application depends on running "show columns" for certain tables. It takes about 60ms to run, whereas all our other queries take under a ms. Querying information_schema directly is even slower. ...
2
votes
5answers
268 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 ...
1
vote
2answers
390 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
294 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
646 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
975 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 ...
22
votes
5answers
20k 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
5k 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
735 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
15k 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
251 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 ...
18
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 ...
7
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
29k 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
302 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
320 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
631 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 ...