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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7
votes
1answer
416 views

Why adding SQL Server user to “Perform volume maintenance tasks” improves the speed of database resizing so much?

If I want to create 5GB database with CREATE DATABASE [test] CONTAINMENT = NONE ON PRIMARY ( NAME = N'test', FILENAME = N'E:\2012\test.mdf' , SIZE = 5529600KB , FILEGROWTH = 1024KB ) LOG ON ( ...
2
votes
1answer
51 views

PostgreSQL 9.x: a clustered index on column A is the same as creating a table ordered by A?

Reading the official PostgreSQL documentation for version 9.0 I read an interesting escamotage that performs better than CLUSTER for big tables: The CLUSTER command reorders the original table by ...
1
vote
1answer
25 views

How compiled are prepared statements?

I found this explanation of how prepared statements are compiled, but I'm still unsure. What exactly is "compiled" in the context of a prepared statement? Is a C compiler executed to create a custom ...
1
vote
2answers
46 views

Should I normalize my string arrays, or just keep it a simple string?

I am working on a project involving cards from the Magic: The Gathering game. To be of any use, I must load the basic information about each card into my database, but some of the fields may contain ...
0
votes
0answers
9 views

Store 100 GB of N-gram and fast access the N-gram [on hold]

I have a scenario where I want to store 100GB of N-gram like ngram = "who is" count = "1233432" where ngram and count are the field names. Just like this, I have billions of records whose approx. ...
-4
votes
1answer
43 views

Create database unique Surrogate Keys without using GUID’s

What is the best way to get database unique surrogate keys in Microsoft SQL Server when using something like “auto increment” as opposed to GUID's. The purpose is to increase performance over using ...
0
votes
0answers
38 views

Very high CPU caused by mysql service

A running mysql service uses CPU in a crazy way. (See attached screenshot from htop) I followed the instructions here with no luck. My server specs: CPU: 1900Mhz . Intel Hexa-Core Xeon E5-2420 ...
1
vote
0answers
20 views

Postgresql: Partition table by hour

I have a system that inserts several million records over the course of 24 hours. Users don't care about the data that's older than 24 hours, and typically query data over a small time frame (5 to 60 ...
1
vote
4answers
42 views

with MySQL, are multiple single column indexes faster than one multi-column index? [closed]

I have a performance related question, in MySQL, are multiple single column indexes faster than one multi-column index?
3
votes
1answer
92 views

Biggest wait WriteLog

I have been given a server (SQL Server 2008R2 64 bit) where our application is running. There has been a gradual decrease in the performance of the application. Now it has come to a point where ...
0
votes
1answer
47 views

Best query to exclude existing friends from query

I have a User table / id_user / username / .. friends table (pair AB and BA): / friend_of / friend_to and a friend_request table (used for pending friend requests) / id_req/ sent_from / sent_to ...
0
votes
2answers
122 views

Make DB tables customizable from an Admin

I want to build an commercial product promotional mobile application in which the administrator of the app will be able to customize some texts / pictures or whatever from the database that ...
4
votes
1answer
62 views

What is the performance impact of queries against DM objects using DMVs in SQL Server 2008?

Recently, I've been running queries against our production system on the DMVs for querying the plan cache. In particular, here's the from clause of the query: FROM sys.dm_exec_cached_plans AS cp ...
0
votes
1answer
25 views

Get statistics of slow running queries

My database application runs many different queries. I have set log_min_duration_statement to 1000. But queries logged there are not always slow, most times they just take a few ms. Is it possible to ...
-1
votes
1answer
27 views

Query optimization and takes less execution time

CASE-1: SELECT * FROM A JOIN B ON B.CustomerID=A.CustomerID CASE-2: SELECT * FROM A JOIN (SELECT * FROM B) C ON C.CustomerID =A.CustomerID Which CASE is efficient ?
0
votes
0answers
44 views

MySQL 5.6 and MariaDB extremely slow

I have MariaDB 10.0.15 and MySQL 5.6.0 (compiled and running on different port) on my server (Debian Wheezy). I have also MySQL 5.5 installed. I have tried import of large database, but I have found ...
0
votes
2answers
31 views

Best database for a real time application [closed]

I am a student doing my Final Year Project where I need to build an android application for on the road navigation. The problem is the application has a feature that alerts the user of nearby incoming ...
0
votes
1answer
18 views

How to define the table structure for measured data in sqlite

I have an embedded system with an sqlite database. How should I define the table structure for the measured data from 4 sensors? Each sensor give us every second an numeric measured value. The ...
2
votes
0answers
24 views

Performance of bitwise operators on byte column vs individual bit columns

I'm designing a database schema at the moment, but have a performance query. Our table needs to have (at least) two flags, or boolean values. We can call these IsComplete and IsExportable. The ...
0
votes
1answer
45 views

Slow ranking values in MySQL

I have a table of around 30 million retail products, with various INT columns that describe sales counters and pricing at different retailers. I'm supposed to display well over 70 different rankings ...
1
vote
0answers
64 views

Database performs differently on the two same Xeon E3 1270-v3 Quad Core machines [closed]

Configuration: RAM: 16 GB DDR3. HDD: Seagate 500 GB 7200 3Gb/s 3.5 inch SATA - idential disks. Postgres 9.4, tried with 9.4.1 also Windows 2008 R2 Web Tried these tunings: work_mem = 32MB ...
2
votes
1answer
79 views

Indexing nvarchar(128) in SQL Server

Have no idea how indexing works in SQL Server. Working with a SQL Server 2012 Intel Xeon 2.2 GHz dual core 8 GB RAM. Will indexing a nvarchar(128) in addition to int primary key cause any ...
3
votes
0answers
77 views

Slow transactions, many locks

At high load conditions the server app stops responding to client because begin/commit statements are executing very slowly (some take 15 seconds). The queries are simple - insert, update two columns ...
3
votes
1answer
78 views

Is a clustered index on a child table in a parent/child relationship the most optimal index?

A clustered index will sort row data in a table according to the ordering of the fields in the index. If so, why would you (or would you not) want to create a clustered index on the child table in a ...
0
votes
2answers
35 views

Is it a good idea to add a reserved field to a large MySQL table?

As you may know adding a new column to a MySQL table with millions of records is hard and in some cases impossible. Is it a good idea to add a text column to each table (say, meta) to save some ...
1
vote
2answers
86 views

Improve performance of converting a large xml file (~300 MB) to relational table in SQL Server

So this is what I have so far: --Read xml content into a XML data type variable DECLARE @FileData XML SELECT @FileData = CONVERT(XML, BulkColumn) FROM OPENROWSET(BULK '\\file_path\test.xml', ...
1
vote
1answer
30 views

Does the length of the index name have any performance impact?

This may seem silly, but in trying to stick to my standard nomenclature when naming indexes in our DB, the latest one was a little lengthy, and like all things DB I wondered if it in any way could ...
0
votes
2answers
28 views

MySQL Image Queries

I have table employees in MySql database with Id, Name, Gender, HireDate, Photo. Photo field is blob. Now when I run this query: SELECT id FROM employees WHERE Photo IS NULL ; it takes forever to ...
0
votes
1answer
47 views

Application is hanging when database upgraded from SQL Server 2000 to SQL Server 2008 R2

Presently we are working with SQL Server 2000, the database is perfectly working with our software for retail sales counter application developed with VB 6.0. But after upgraded to SQL Server 2008 R2, ...
0
votes
1answer
56 views

MySQL always writes simple temporary/memory tables to disk (both tmp_table_size and max_heap_table_size are set to 8GB)

I'm struggling with this issue and just can't figure out why this is happening. CREATE TABLE sitecache._test ENGINE=MEMORY SELECT * FROM website.gallery_likes WHERE 1=0; Every time I execute this ...
1
vote
1answer
73 views

Non-sequential Primary Key performance in PostgreSQL 9.3

Due to requirement to support distributed environment, each of my clients has been assigned unique node id, it appends the node id with running number as primary key and stores at local database. E.g. ...
4
votes
0answers
85 views

Timestamp-based index

I have a big database (200GB+) that contains some log info. And I want to speed up SELECT queries and stored procedures. I have a table with a GeneratedOnUtc datetime column, and have a non-clustered ...
0
votes
0answers
25 views

redshift performance effect if use 32 character long unique string as Primary key instead of auto incremented int

In my analytics application I am creating 32 char long unique string for each hit as user_session. In current implementation, I am storing user_session in tbl_sesssion in session column and I am ...
0
votes
2answers
22 views

Can I extrapolate from the progress reporting in MyISAM ALTER?

I'm migrating a 300 million row MyISAM table to add some indexes. Just because it might be relevant, here's my ALTER statement: ALTER TABLE my_table ADD UNIQUE INDEX my_table_abcd (a, b, c, d), ...
2
votes
1answer
74 views

Oracle 11g connect overhead

Currently one of our new applications is connecting to an Oracle 11g instance over 30,000 daily (at every user request) via their application server, using the same account. (it will be significantly ...
0
votes
0answers
31 views

Multiple subqueries performance issue

I have a query that collects customer data. I select a lot of correlated data from different tables. I want to have only ONE result row for each customer. The query looks like that: SELECT c.Id ...
0
votes
1answer
29 views

Reusing covering index for fields in FROM, from another query's index

For the following query I have a covering index as so: SELECT bar_id FROM foo WHERE user_id=:user_id AND date_sent=:date_sent; ALTER TABLE foo ADD INDEX (user_id, date_sent, bar_id); Now I have ...
1
vote
1answer
94 views

Query on 250 million records

I have a table with below structure CREATE TABLE [dbo].[ColumnValues]( [Id] [int] IDENTITY(1,1) NOT NULL, [ColumnId] [int] NOT NULL, [Value] [nvarchar](max) NULL, [OutputArea] ...
0
votes
0answers
44 views

PostgreSQL Performance - Many Large Databases

I run an internal (development) database server containing 25 databases each ~71GB in size. There are usually between 50 and 100 active connections at any given time. What can I do to help improve ...
0
votes
1answer
21 views

Query running slow on script and producing error 500 when run in phpmyadmin

I have a query that seems to take a good 30 seconds to execute even when the query produces no results. There are 4000 lines within the database and queries that produce all results run within ...
2
votes
1answer
38 views

io_stall question

I just installed SQL Server on new hardware and ran a test script to show io_stall information by file. Nothing else has been loaded yet, just a fresh install of SQL Server 2012. Why are the ...
0
votes
1answer
42 views

Improving lots of Left Joins ( SQL Server 2008 - procedure )

This query is running with 8 minutes to complete. I'm trying to help the programmer with this task. I've created indexes and stats, update_stats and rebuild indexes but none of this is helping us. ...
0
votes
0answers
23 views

Performance/Maintenance Implications of a Write Heavy Table In An Otherwise Normal “CRUD” Database

We have a small-ish (<100,000 rows) MySQL database (on Amazon RDS). Its supporting a fairly simple read heavy CRUD web application. Currently we're building out a web analytics system. It will ...
1
vote
1answer
226 views

Designing a High Score/Leaderboard table

I'm looking for input on how to design a highscore table for a game I'm creating. The database I'm using is postgres. That's not really something I can or want to change (unless there's very good ...
1
vote
2answers
155 views

OLAP or OLATP - How to determine

I have SQL express server with database that is used by one application. I am trying to optimize the DB but am not sure if the DB is OLTP or OLAP. There is no analysis server installed, the DB is ...
0
votes
0answers
52 views

SELECT query on mySQL taking 20 seconds to execute

Many points to note: This SELECT statement is happening both on my site, terminal, and on phpmyadmin, so the problem isn't a coding problem. If you delete the 11,000,000 rows and keep 20,000 rows ...
6
votes
1answer
483 views

Would index lookup be noticeably faster with char vs varchar when all values are 36 chars

I have a legacy schema (disclaimer!) that uses a hash-based generated id for the primary key for all tables (there are many). An example of such an id is: 922475bb-ad93-43ee-9487-d2671b886479 There ...
0
votes
1answer
41 views

MySQL performance of applying unique constraint single column vs combination column

I have a large MySQL InnoDB table containing around 137 million rows. I need to add a unique constraint to the table. We have two options: 1) A combination index on three columns, one of which will ...
5
votes
2answers
165 views

Feasible to have thousands of users in Postgres?

We are creating SAAS where we will at most have 50.000 customers. We are considering creating a user in the Postgres database for each customer. We will map each user that logs into our service to a ...
0
votes
1answer
80 views

MYSQL: How to improve performance of inserting over 1M rows to a table with over 100M indexed rows

I have this mysql table: CREATE TABLE `codes` ( `code` bigint(11) unsigned NOT NULL, `allocation` int(11) NOT NULL DEFAULT '0', `used` tinyint(1) NOT NULL DEFAULT '0', PRIMARY KEY (`code`), ...